ANNEX 1: 1. TECHNICAL SPECIFICATIONS: DOUBLE REGULATING TURBINE GOVERNOR 1.1. Type and Description The turbine governor shall be provided, complete with actuator, guide vane, governor cubicle, restoring mechanism & transmitters, motor-driven oil pumping units, pressure tank, sump tank, operation oil, oil piping, guide vanes servomotors, speed sensing equipment, hydraulic overspeed device, regulating ring hydraulic operated lock, hydraulic operated cooling water valve and all parts and accessories required to make a complete unit for regulating the speed and controlling the guide vanes of the turbine in accordance with the requirements specified below. The governor shall be of the proportional – integral –derivative [PID] Numerical Electro-Hydraulic type and shall be guaranteed by the Contractor to fulfill the requirements of this Specification. The governor shall be protected from the effects of electrostatic discharge, radiated electromagnetic fields and conducted or induced fast transients or bursts of noise. The governor shall be designed so that electromagnetic interference does not cause mal-operation of the control system or damage of the components. The Contractor shall explain his design basis for electromagnetic tolerance. The necessary apparatus and auxiliary devices shall be provided to facilitate interface to the Unit control system via hard wired interface. 1.2. Operating Requirements The governor shall be equipped with all necessary automatic auxiliary devices to permit full automatic operation of the starting, build up of speed, synchronizing and pick-up of load to pre determined manual setting, load/frequency regulation and stopping of the turbine – generator unit. The governor shall be capable of controlling the speed of the turbine stably when operated at no load, or when operated at the rated speed with isolated load at any power output. The governor shall also be capable of controlling the output of turbine at any power output when operated in parallel with other generators in the plant or in the transmission network. During normal operation, regulation of unit power and network frequency are according to actual frequency reference [i.e. frequency influence], power reference and permanent speed droop value. 1.3. Governor Components The governor shall be complete with the following items. The Contractor is to ensure that all necessary items are supplied, whether or not they are specified herein. 1.3.1. Control Unit This shall comprise an electro-hydraulic transducer which converts an electrical regulating signal into a hydraulic valve movement and causes the turbine guide vanes to move in a direction and to an extent demanded by the regulator. 1.3.2. Guide Vane Distributing Valve This valve shall control the flow of pressure oil to and from the guide vane servomotors.

1.3.3. Guide Vane Auxiliary Distributing Valve This valve shall be supplied and arranged for direct manual control of the turbine guide vanes. An auxiliary selector valve shall be provided to change from main distributing valve control to auxiliary distributing valve control. An indicator on or near the actuator shall be provided to show which type of control is selected. Push buttons for raise/lower control of the turbine guide vanes shall be installed in the turbine Governor control panel for use when operating the guide in manual position. 1.3.4. Guide Vane Limit Mechanism This function will limit the maximum and minimum guide vane position both during the start sequence and normal operation. Limitation to prevent operation of reverse power and operating on zones where cavitation can occur shall be provided. The Unit Automatic Control equipment will initially open the limiter to a predetermined value upon closing of the Generator breaker (preferably 80%). Afterwards the limiter device can be controlled freely from the control room to any setting by the operators. 1.3.5. Guide Vane Locks The servomotors shall be equipped with locking devices that shall be capable of maintaining the servomotors on either the fully open or fully closed positions. The closing lock shall be automatically applied when the unit is shut down such that the guide vanes shall remain fully closed against maximum reservoir level even if the oil pressure is reduced. The closing lock shall be released as part of the start-up sequence. The open position lock is to be applied manually to ensure operation safety while working within the turbine with the guide-vanes in open position. Both locks shall be capable of resisting the maximum force that can be applied at the oil pressure was inadvertently applied and shall be interlocked with the unit start-stop system. Alternative locking arrangements which achieve the same performance will be considered. Limit switches shall be installed for status indication on the position of the locks. These shall be connected to the control system for start/stop interlocking. All necessary supply and return oil pipes etc. shall be provided and installed in accordance with the standard technical requirements. 1.3.6. Emergency Shutdown mechanism The Hydraulic control assembly shall be able to close the guide vane servomotor in the event of malfunctions such as:-

Failure of the Governor Power supply. Failure of an element in the control loop Minimum pressure in the pressure oil system

In order to fulfill the above safety requirements, an emergency trip command signal shall be included in the hydraulic loop. This loop shall comprise of emergency trip acting valves to include:- The minimum pressure emergency trip valve. The solenoid valve for electrical trip signals.

By spring action during the emergency situation these valves shall change over from the operating position to the emergency trip position and hence closes the guide vane servomotors. The valves shall be provided with auxiliary contacts, which indicate when the device are energized and de-energized respectively. The equipment shall be rated for continuous duty on 110 V D.C. . 1.3.7. Restoring Mechanism The actual position of the servomotors and the distributor valves for the Guide vanes will be given by position transmitters. Two redundant position transmitters for the servomotors and distributor valves shall be required such that a failure in one will not affect the operation of the positioning controller and an alarm will be indicated.

The position transmitters shall be mounted appropriately and their connecting cables shall be connected to the governor electronic cubicle with properly screened cables, which shall be routed to minimize the possibility of interference or damage. The mechanism shall be complete with all supports, clamps, brackets, protection against mechanical damage and any other item required to complete the installation. 1.3.8. Hydraulic Mechanical Overspeed The turbine shaft shall be equipped with a suitable mechanical overspeed detector which shall apply full oil pressure to the closing side of guide vane servomotors. The operating speed shall be adjustable but will be initially calibrated to operate when the turbine speed is 140%. The mechanical overspeed device shall be fully interlocked with the unit tripping and shall in parallel with its direct action an emergency shutdown. The device shall be reset manually. Appropriate guard will be provided for the sensor device assembly. Electrical contacts rated at 250 V 6A shall be interfaced to the Unit electrical tripping scheme. 1.3.9. Speed Signal Generator Unit speed shall be measured with either the following methods:-

Use of system VT and generator VT measurement to synthesize the respective frequencies.

Use of inductive switches: Two inductive detectors that shall be driven by a toothed wheel to be mounted on the turbine shaft. The Contractor shall submit a proposal on how to mount the toothed wheel to the turbine shaft in situ. The Contractor shall provide suitable cover or guard for the speed detection device. The signal shall be transferred into the processor speed device, which will transform it to the required form. Failure of one of the inductive detectors will not affect the operation of the governor equipment and an alarm will be issued. If both inductive detectors fail, automatic changeover to manual governor mode procedure shall be activated.

1.3.10. Alarm, Trip, Indication and Control Devices Protection functions shall be included but not limited to the following: Failure of both inductive detectors for unit speed measurement or VT measurement. Failure of servomotor position transmitter measuring device. Actuator device not responding.

Digital governor failure. Failure of both power supplies. The above protection function shall initiate emergency shutdown procedure of the unit. All faults messages shall be indicated both and hard wired to the unit control board. Quantities shall be indicated at the Governor cubicle but not limited to the following: Guide vane position Turbine speed Guide vane limiter position Actual power output Penstock and Tailrace pressure Governor oil pressure Net Head All governing system alarms and trips functions shall be indicated by approved means at the Governor Cubicle. These are all abnormal conditions that may arise in the system. These systems includes but not limited to the followings: Governor processor Pressure receiver accumulator Sump Tank Speed measuring system Oil Level Loss of oil pressure Governor Pumps These shall also be hard wired to the unit control board. The control features that shall be provided shall include but not limited to the following:- Selection switches, key operated

Operation/Parameter selection Manual/Automatic selector Local/Remote operation

Control Modes selection pushbuttons Speed Control – Network Speed Control –Isolated Load Control with selectable frequency influence via selector switch. Opening Control

Push buttons for start, stop power Set point adjustments(raise/lower) Load/power analog set-point Limiter set point(raise/lower) Governor manual control adjustments Checking and changing of governor parameters.

The governor commands shall be possible from both the governor panel and the Unit Automation depending on the selection of the governor control (local /remote). These shall also be hard wired to the unit control board.

1.3.11. Electrical Control Devices The governor shall be complete with the following items. The Numerical electronic control unit shall be housed in one floor standing panel/cubicle.

1.3.11.1. Numerical Electronic Control Unit. A modern numerical based electronic unit of the PID type shall be supplied to control the position of the guide vanes.

Speed adjustment device with a range of 90 to 110% of the rated Speed adjustable while the turbine is operating. This device shall be controlled at this panel and also electrically from the control room.

Power adjustment device with a range of 0 to 100% full load adjustable under the turbine loaded. This shall be controlled at this panel and also electrically from the control Room. Gate limiting device shall be provided to be controlled manually at the panel and also electrically from the control room. The control unit shall introduce the necessary stabilising and correction signals and transmit the governing signal to the electro-hydraulic control unit of the guide vanes.. Protection against high voltage surges and transients shall be provided in all systems using solid state components. The surge protection shall be adequate to protect against system or component failure from either externally or internally produced surges. 1.3.11.2. Main Processing Unit and Memory The main processing unit and memory shall be suitable sized for the application. The Contractor shall provide details of the equipment proposed. This information shall include the unit configuration, memory structure, type and capacity, execution times, the effects of adding peripherals and a description of the diagnostic functions. The Governor Equipment shall be capable of I/O forcing and simulation, for test, commissioning and maintenance purposes. These functions shall be facilitated through a locally connected programmer. The I/O forcing shall be only be possible by use of security passwords or key switching. The Governor Equipment shall be programmed by high level programming language that is user- friendly. Windows pull down menus and mouse control interface software shall be provided. 1.3.11.3. Supervision of Governor Controller Comprehensive self testing and self diagnostic facilities are required to be included in the Governor equipment. The monitoring of the governor controller shall include but not limited to the following functions. The Contractor shall provide details of the following facilities offered:

Correct application program scanning check,

Memory integrity checks.

Validity of data exchange between memories, processing units and I/O modules.

Power supply check

Main processor unit status check,

I/O channel integrity check.

Error message display

Integral supervision functions

Powerful aid for testing

Other self test and diagnostic execution details.

Self monitoring of the processor

Process connections

Actuator and transducers

Speed sensor failure. The Contractor shall also provide details of the facility proposed for reporting the self test and diagnostic message. Output contacts shall be provided for external fault indication and interfaced to the unit control board. 1.3.11.4. Synchronizing Speed Control/Frequency matching. During the synchronizing, the network frequency with a small deviation (beat frequency) will be used as frequency reference. The difference between generator and network phase angle will then periodically be zero, making it possible to synchronize the unit. However, a selector control shall also be provided to allow the governor’s internal frequency reference to be used and at this time the frequency reference shall be adjustable using raise/lower push buttons or the synchronizing relay mounted on the unit control board. A selector switch shall be provided to select between frequency matching by governor itself or by the auto synchronizer. The selector may be implemented in the Automation (unit Control Panels). The governor shall ignore the commands from the auto synchronizer when selected to do the function of frequency matching. 1.3.11.5. Power and Frequency measurement The Generator’s current metering transformer and the Network’s voltage transformer shall be used as a source for measuring power. Network frequency shall be measured from the network voltage transformer. The accuracy of the frequency measurement shall be higher than 0.01%. The accuracy of power measurement shall be higher than 1%. Current transformer terminals blocks shall be furnished with short circuiting facilities to short the main CT such that secondary injection tests can be performed without open circuiting the CTs. The design of terminal blocks shall be such that measurement of secondary currents shall be possible while the unit is running. 1.3.12. Governor Power Supplies The Governor Control voltage shall be 24Vdc supply. Dual redundant power supplies shall be provided and shall draw power from both DC and AC sources as follows below:-

DC supply -110 Volts Nominal [Range +15 % /-20%]

AC supply - 240 Volts 50Hz Nominal [Range +5 % /-10%] Failure of one source of supply shall not affect the operation of the governor equipment. An output contact indicating failure of any of the power source shall be provided. The primary and secondary voltages of the power supply shall be galvanically isolated. For lighting and heating of the cubicle 240Vac 50 Hz supply will be used. Cubicle lighting shall be controlled by a door switch. 1.3.13. Manual Control Mode facility Manual control facility shall also be provided in form of electronic cards for control of guide-vane servomotor. The cards shall have mode selection (manual/Auto) and necessary controls and indications. In auto mode, the control of guide-vane servomotor shall be by the governor signal. 1.3.14. Net Head Signal Equipment Dam level and Tailrace level equipment shall be provided for real time dam level monitoring. The outputs from these devices shall be used by the governor to determine the net head. The mounting position of the dam level transducers shall be agreed upon during the preliminary design stage. 1.3.15. Speed Monitoring System Speed monitoring system shall be provided. The system shall serve to detect measure, evaluate and monitor machine Rev/Min signal up to 200% nominal speed. The system shall be driven by two inductive pick-up sensors driven by the toothed wheel (mentioned under governor speed sensing device) or frequency measured from the system and generator VTs. Failure of one pick-up sensor shall not affect the operation of the system but an alarm condition will be indicated by an output contact. Detection of failure on one or both of the pick-ups shall be incorporated and wired via relays on to the output terminals. Two additional separate electrical overspeed devices complete with inductive speed pick-up shall also be provided. 1.3.16. Speed Level Detection The system shall have at least 6(six) monitoring speed level that can be set to operate within a range of 3- 200% of the nominal speed. Output interposing cut-off relays contacts shall be SPDT with rating of 250Vac, 6A or better, shall be provided. 1.3.17. Analog Output Signal The system shall have mA output signal (4 – 20mA) to the unit control board for the following functions:-

Speed Indicator with red mark at unit rated speed

Guide vane position.

Limiter position

Governor oil pressure

1.4. Governor Cubicle construction The Governor cubicle shall be of rittal standard, floor-mounted and free standing construction for indoor installation with cable entry from the bottom. Ventilation points shall be provided with suitable removable air filters to prevent the ingress of dust and insects. Cooling air fans shall be incorporated in the Governor equipment Cubicle size and colour shall match the Unit Control cubicles. The Governor cubicle shall be of tropical design and to IP54 Protection code of practice according to IEC529. The cubicle shall be fitted with lifting eye bolts which shall be removed after installation. All metal parts other than those forming part of an electrical circuit shall be connected in an approved manner to separate earth bars running along the bottom of the panel. The metal cases of all instruments and the like shall be connected to the copper earth bars by conductors of not less than 2.5sq mm or by other approved means. Doors shall be fitted with handles and locks [key operated]. The cubicle shall contain internal power sockets. Door operated cubicle internal lighting shall be provided. All instrument and control devices shall be easily accessible and capable of being removed from the panel for maintenance purposes. Labels permanently attached to the panel shall identify each relay and electronic card within the panel and adjacent to the equipment concerned. All control relays shall be robust and firmly supported on their bases by use of retainer clips or springs to avoid looseness that may occur due to vibration. The cubicle shall be made of sheet steel not less than 2.0mm thick. Devices and component shall be mounted and labeled according to number and function. The Governor Equipment cubicle shall have terminal blocks for reception of cables cores (2.5 mm2) for interfacing to the other plant control equipment. All wiring shall be of adequate cross section area to carry prospective short circuit without risk of damage to conductors, insulation or joints. Wiring shall be supported using an insulated system, which allows easy access for faults finding and facilitate the installation of additional wiring. Ribbon cables cables with plug and sockets connectors may be used for light current wiring. Plug and socket connector shall be polarized so that they can be inserted into one another in the correct manner. All wiring shall be identified in accordance with the associated schematic and/or wiring diagrams by means of discrete wire numbers. All internal electrical wiring for the governor cabinet shall be neatly terminated. All wiring shall be insulated with 600-volt grade oil-proof material. All connections shall be made at terminal blocks. Terminal blocks shall be provided and rated not less than 600-volt, and shall be provided with covers. At least 10 per cent extra terminals shall be provided in each group or terminal blocks. Permanent identification of all terminals wires shall be provided. A consistent system of wire numbering approved by the client shall be used throughout the equipment.

1.4.1. Peripherals and Software Package All peripherals to the Governor Equipment, such as programming units shall be supplied as part of this contract. Client staff shall be trained on how to these equipment for plant maintenance and future plant modifications. The programming unit shall operate at 240V, 50Hz. The software package with the necessary license shall be provided. The Contractor shall provide details of the facilities to be included. This shall cover the method of programming program storage, program loading and program documentation. Any modifications to an existing program shall be protected by password or key-switch security. The portable programming units shall be capable of providing the facilities for local Governor fault finding, self diagnostic facilities and commissioning. Details of the programming, de bugging, maintenance, fault finding and diagnostic facilities shall be provided by Contractor. The necessary software build to operate under windows environment shall be supplied. The software will display the signal values/level in the Governor on the screen of the portable device in an analogue manner. The software will provide functions to modify, store, compare the running program with file, test and for graphical documentation of the program. A hardcopy of the software program including all the parameters setting and range shall be provided in the documentation. The operating software shall also be provided in a CD form for future loading into another PC. Cable to connect the PC to the governor equipment shall be supplied. 1.5. Training: A comprehensive training on the governor, operating software and control PLC algorithms shall be conducted by the contractor to client Engineers to equip them with sufficient knowledge on how to maintain and carry out future modifications on the Governor system. This shall be done before the commencement of the factory acceptance tests. A five (5) Tier training program is recommended as follows to help in attaining full technology transfer to client Engineers:

a) Basic Training prior to project programs development to absorb the software general concepts

b) Participation in project programs development during design(attachment to Contractor) c) FAT participation testing d) Participation in commissioning of the project program (attachment to Contractor) e) Site training in the configured project programs

The contractor shall present a training proposal that shall be discussed and agreed upon with the client during the preliminary design. 1.6. Facilities to enable Remote Regulation.

The governor shall be designed to accept the following control commands/functions from the unit control board.

start/ stop commands

Raise and lower commands for power /load control

Raise and lower commands for limiter position

load/power analog set-point

Selection command between load regulation by Raise/Lower commands and Analog set-point shall be provided.

Selection of all governor control modes. Speed Isolated Speed Isolated Network Operation Load Control – with inbuilt frequency threshold band outside which the governor

will automatically change-over from load control to speed control Isolated Load Control with selectable frequency Influence.

Shutdown commands (Emergency tripping). Load control shall be in two ways:-

a. Using the Digital Raise/Lower commands.

b. Using the analogue set point.

If the Raise/Lower commands are operated when the analogue set point is ON, these shall take priority. The necessary feedback signals shall be provided to the automation via hard wired interface. 1.7. Facilities to enable Local control Regulation. The following command shall be established to enable control of the governor from the local panel.

start/ stop commands push buttons

Raise and lower commands for power /load control

Raise and lower commands for limiter position

Selection of all governor control modes. Speed Isolated Speed Isolated Network Operation Load Control – with inbuilt frequency threshold band outside which the governor

will automatically change-over from load control to speed control Isolated Load Control with selectable frequency Influence.

1.8. Cables and Cabling Works Cables shall be provided for interconnections between the Governor equipments/devices to the Unit Automation system and Power supply boards. The cable shall be shielded and steel armoured. These cables shall carry all the signals including the power supplies. The ends of the cable to the governor components shall be provided with appropriate plug and socket connectors that shall be polarized so that they can be inserted into one another in the correct manner for easy removal during maintenance. Cables shall be well labeled at both ends. Necessary cable support systems shall be provided.

1.9. Governor Oil Pressure Supply Equipment The oil pressure system shall be designed for use to control the Guide vanes, the MIV and by pass systems and the cooling water valve. This equipment shall be designed to supply sufficient pressure oil to the guide vane servomotors via the governor and distributing valves to open and close the guide vanes through their full travel. It shall include but not limited to the following:- An oil sump, One pressure tank/accumulator, main and standby governor oil pumps, piping, valves Cooling system all other ancillary items to form a complete installation

The equipment shall be designed to minimize the requirement for site commissioning and shall as far as possible consist of a single assembly which can be factory tested prior to shipment. The main control valve shall be directly controlled by the start/stop valve and shall form part of the oil supply assembly. The control valves and associated equipment shall preferably be assembled from standard CETOP components and mounted on a common valve block. The contractor shall provide the operating oil for the governor system. 1.9.1. Sump Tank The sump tank shall have a capacity of at least 110% of all the oil in the sump and pressure tank(s) under normal operating conditions. It shall be designed to carry the two motor driven oil pumps and shall be provided with a manhole for access to the interior; an oil level gauge; operating oil; oil fill and drain connections; and oil purifier connections. A breather shall be fitted on the sump tank and shall incorporate a moisture filter. Two PT100 temperature detectors shall be also incorporated to monitor the oil temperature. Sight oil gauge shall be furnished. All control and monitoring equipment [i.e. low, pump stop level, normal & high oil level, continuous level indication [4-20mA], etc.] for efficient operation shall also be provided. 1.9.2. Oil Pumps and Auxiliaries. Oil pumping set with duty and standby pump motors shall be provided. Each pump shall be self-priming at any time after the units are commissioned. The pumping set shall be complete with sump tank, duty/standby electrically driven pumps, valves, monitoring devices, duplex filters (with pressure differential alarm), high and low tank level switches and all other parts necessary to integrate the system into the unit control system. When the turbine is running the duty pump shall run continuously to maintain the system pressure. Pump operation shall also be supervised by a pressure switch for alarm. The standby pump shall operate under pressure switch control. The pumps shall be rated such that the standby pump will not start when the guide-vanes are moved through a full opening stroke followed by a full closing stroke with initial oil pressure at minimum of the range of duty pump operation. Pump operation shall also be supervised by a pressure switch.

It shall be possible to select any pump to duty or standby. ‘Standby pump running’ alarm shall be provided. The pumps local control operation shall be provided in a separate panel. The panel shall house the local controls for the governor oil pumps. State indications, current consumption ammeters and associated CTs, running hour counters, start/stop push buttons, fault indication, pump selection switch, emergency stop buttons and key operated selector switches for local and remote operation shall be provided. All necessary signals shall be interfaced to the unit control board. The oil pumps shall draw power from the new 415 board that shall be supplied under this contract. The specification of this board is indicated elsewhere in this document. The board electrical components [i.e. pump contactors, switches, indicators, overload protection, fuses and it’s carrier etc] shall be designed in order that the circuit functions/copes to requirements of the new oil pump motors. The pump motors will be arranged for direct on line starting with the pump unloaded. The control system shall be arranged such that the pumping unit remains operative following a failure of the unit on start/stop system such that the system can be operated under manual control. 1.9.3. Governor Oil Cooling System Separate oil cooling system shall be provided with heat exchanger, oil circulation pump, piping for both oil and water, valves, cooling water flow meters (contacts and continuous flow), PT 100 for inlet and outlet cooling water temperature monitoring and any other necessary materials. The heat exchanger shall be of a suitable material for the application to the approval of the client. Cooling water shall be drawn from the Penstock through a hydro cyclone for each river. Strainer device shall be provided in the oil circulation circuit and an alarm shall be provided if the differential pressure across the strainer exceeds a threshold. Provision shall be made for oil refilling to the sump by external means. The oil circulation pump shall have two operation modes:- Auto -by sump oil temperature Manual – by ON/OFF push buttons The oil circulation pump shall draw power from the new 415 board that shall be supplied under this contract 1.9.4. Pressure Tank/Accumulator(s) One tank of welded construction shall be provided having a volume capable of operating the guide vanes three full strokes and the MIV two (2) full strokes at the rated minimum pressure and oil level. The tank shall be fitted with the following items and any other items required for the safe and efficient operation of the oil system: -

Pressure Relief Valve One automatic pressure relief valve of adequate capacity mounted at the top of each tank.

Sight Oil level Gauges

One oil level gauge to indicate the oil level in each tank. Each gauge shall be fitted with a metal guard, stop valves and automatic shut-off devices to prevent the escape of oil in the event of glass breakage.

Oil level Alarms High and Low oil level alarm devices each electrically-independent and arranged to close to give alarm. The high level alarm device shall be set at a level to indicate failure to maintain the oil volume. The low level alarm device shall be set to operate when there is only sufficient oil left in the tank to provide two total servomotor volumes. Further oil level switches may be necessary for automatic pumps stop when the level of oil in the sump tank is below the operating level.

Pressure indication and control Switches The following shall be provided:

Pressure gauge for local indication of pressure. Transmitting unit for connection to local pressure indicator and remote pressure

indicator at the generator control panel. Pressure switches

Ancillary Items The tank(s) shall be provided with the necessary connection for the pressure lines with shut-off valve; man-doors; drain connections; lifting lugs; and foundation bolts, nuts, washers, etc. to complete installation.

1.9.5. Guide Vane Servomotors Two oil pressure servomotors shall be furnished to connect to the guide vane operating ring by means of two push/pull rods having adequate length adjustment facilities. The servomotors shall be provided with an oil pipe work system connecting them to the governor oil distributing valve. At minimum oil pressure, the double-acting servomotors shall be capable of moving the turbine guide vanes through a full opening stroke or a full closing stroke at the rated closing time with maximum gross head plus maximum water hammer pressure acting on the turbine. At this pressure, the servomotor shall be capable of holding the turbine guide vanes closed to prevent the runner rotating. The assembly shall be designed to withstand the maximum reaction in either direction. The arrangement shall be such that the total guide vane operating force shall be divided approximately equally between the two servomotors which shall direct their efforts to opposite sides of, and tangentially to, the guide vane operating ring. The system shall be designed such that failure of any pipework will not allow fast closing of the guide vanes. The cylinders, pistons and piston rings shall be of approved materials chosen to restore mutual compatibility. The surface of the piston rods shall be hard chrome plated incorporating suitable renewable seals to prevent oil leakage along the piston rod. The cylinders shall be provided with flanged main oil pipe connections, a pressure gauge tapping at each end complete with isolating needle valve, air release valves, and drain connections with pipework fittings and valves.

Each servomotor shall be provided with a device to retard the rate of closing from just below the speed/no-load position to the fully closed position. This device shall not affect the rate of opening from the closed position. Each of the following devices shall be fitted on one or other of the two servomotors, or on the guide vane operating ring:-

A scale and pointer to indicate percentage of servomotor stroke from the fully closed position.

A connection for the governor restoring mechanism. A mechanical locking device of simple construction capable of locking the guide vanes

in the open position and of withstanding safely the maximum operating force of both servomotors.

An automatic hydraulic locking device for maintaining the guide vanes in the closed position. This shall be incorporated in the start-stop sequence of the Unit.

1.9.6. Oil Pressure Piping All interconnecting piping and valves between the oil pumps, sump tank, pressure tank, actuator, distributing valves, and turbine servomotors shall be included in the supply. All pipework and associated fittings on the oil system shall be flanged and if loose flanges are provided for welding on site, springing of pipes into position to make connections will not be permitted. The governor units shall be located in the powerhouse generally but the final layout shall be for agreement between the Contractor and the client. Valves shall be provided such that main items of equipment can be isolated for maintenance. The pipework system shall be well supported and arranged in sections to allow easy dismantling during turbine maintenance. The pipe work shall be arranged so that oil cannot drain from servomotor cylinders, control valves or pipe work when the pressure oil supply is off. Air release points shall be provided on the servomotors and as necessary in the pipe work. 1.9.7. Nitrogen Bottles Nitrogen Bottles for maintaining the governor pressure in the pressure tank (Piston accumulator) shall be supplied. These shall be well connected to the piston accumulator with appropriate pipe work. A pressure gauge shall be mounted on the nitrogen bottles for use during maintenance. 1.9.8. Penstock and Tailrace pressure Indication Ultra-precise pressure transducers and indications for Penstock and Tailrace level shall be furnished and installed in the governor cubicle. Necessary interconnecting cables, pipe work and materials shall also be furnished. 1.9.9. Inspection and Testing

Factory tests

All equipment shall be subject to tests in accordance with relevant applicable standards. All the governor parts (Hydraulic and electrical) shall be tested connected together as a system. This shall include but not limited to: - digital governor, sump tank, pressure tank, nitrogen bottles etc. necessary piping shall be provided for interconnecting the parts to a working system.

The governor acceptance tests shall be performed according to IEC 60308 (Testing of speed governing systems for hydraulic turbines) with the exception that the test items difficult to perform on Site, may be done in the factory. The client shall witness the factory tests.

Site tests during erection and preliminary functional test.

During the installation of each of the equipment tests shall be performed, to establish the accuracy of the assembly and to prove the adequacy of the materials and the workmanship. All tests and test procedures with test recording sheets shall be submitted to the Client at least three (3) weeks to the execution of the Tests. The client shall review and incorporate amendments to the procedures and tests.

The Contractor shall perform the following tests, for all items where applicable, to ensure that the equipment has been correctly installed all necessary adjustments and settings made and that the item is in sound condition to run under load. A. Inspection during installation of equipment

Pressure test of pressure oil tank and piping for pressure oil system

Calibration of dial type thermometers

Calibration of pressure gauges B. Preliminary functional test

Measurement of oil pump discharge pressure

Continuous operation test of oil pump (heat run)

Automatic start and stop test of stand-by oil pump

Measurement of oil pressure build-up time

Capacity test of oil pressure tank

Adjustment and setting of safety valve

Check of oil level control system

Leakage test of oil(tank and all pipe lines)

Setting of oil level and pressure switches

Insulation resistance measurement of motor

C. Operational tests and adjustments

Adjustment and setting of servomotor feedback transducers

Operation of servo valve with numerical governor

Operation of governor manual control

Overall governor operation test at no load

Normal Start and Stop operational tests

Quick shutdown test and Emergency Trip

Setting and checking of adopted times for turbine gate stroke

Preliminary setting of speed monitoring system and operational checks

Adjustment and setting of guide vane closing and opening times

Overspeed tests.

Load rejection tests at 25%, 50%, 75% and 100%.

Relation between guide vane servomotor opening and generator output (output test)

Quick load increase test

Permanent speed droop measurement

Heat run test

D. Performance tests

After the Governor equipment has been installed, tested, and/or its mechanical and dryout runs has been successfully completed and approved and the generating unit has been fully operational, the Contractor shall carry out the performance tests in the presence of the Client to demonstrate that all guarantees and technical particulars as listed in the Tender and Contract Documents have been satisfied and that the entire Equipment is properly installed, free from objectionable defects and correctly adjusted to operate as specified. The performance tests shall include but not limited to the following items:

E. Reliability run After the performance tests and before Taking Over, Contractor shall carry out the reliability run to demonstrate satisfactory operation of Governor equipment and associated devices.

The reliability run shall be carried out under the Contractor’s responsibility. The period of the reliability run shall be 30days. When the Equipment is inoperable due to external fault or any cause beyond the Contractor’s responsibility, an extension of time will be given equivalent to the lost time. Should the external problem persist for more than one week, then the Contractor and Client will discuss and agree on the best way forward. The reliability run shall include the start-stop test of the generating equipment which shall be carried out by the Contractor twice a day during a period of the reliability run.

1.9.10. Spare Parts. The Contractor shall provide spare parts that he recommends should be held by the client to enable the equipment to be operated efficiently for a period of 10 years. The spares shall include but not limited to the following:-

One numerical Governor Unit

One Power supply pack of each type provided in the governor

Three output Relays of each type

Three input relays/opto-coupler of each type

Two speed pick-up sensors

Two position transducers of each type

Two servo valve of each type

Oil filters of each type

Solenoid valves, one of each type

One hydraulic valve of each type

One oil pump of each type complete with motor

One oil circulation pump complete with motor

Sets of oil seals kit

One pressure gauge of each type

One operator panel

One Speed Monitoring device of each type 1.10. MIV and By-pass control system: The MIV and by pass systems shall be operated by the same pressure system operating the guide vanes. Control Valves for control of MIV, by pass and cooling water system shall be established and mounted on the oil sump tank as those of the governor control. The control valves and associated equipment for MIV and by-pass valve shall preferably be assembled from standard CETOP components and mounted on a common valve block on the sump tank. The control voltage to the coils shall be powered via 110Vdc power supply. The closing of the MIV shall be via a counter weight correctly rated to close the MIV at the highest penstock pressure. A key operated selector switch for MIV and by pass control shall be provided. Contacts of this selector switch shall be used to interlock the open/close control commands. The selector switch shall have the following levels of control.

Local/Maintenance control: Control of MIV and by pass valve at the local control panel. Open/close push buttons for both MIV and By-pass intergraded with status indication LEDs (24Vdc) shall be provided.

Remote Control: Control of MIV and by pass valve at the unit control board. Status indication: Robust limit switches shall be provided and mounted on the MIV and by-pass for the following indications:-

MIV open and closed position.

By-pass open and closed position. These limit switches shall be wired to energize robust multiplying relays whose contacts shall be interfaced for both local and remote indication. 1.11. Cooling water valve. A cooling water valve and associated isolating valves for each unit shall be supplied. This shall tap water from the main cooling water line. The cooling water valve shall be operated (close/open) by the governor oil pressure via a bistable control valve.

The bistable control valve shall have solenoid coils operating at 110Vdc and shall be mounted on the same valve block where the MIV and by pass control valves are mounted. Limit switches for valve status indication shall be mounted on the cooling water valve and interfaced to the unit control board.

ANNEX 2: 2. TECHNICAL SPECIFICATIONS: PLANT INSTRUMENTATION 2.1. Introduction The new Wanjii units shall be equipped with modern instrumentation for control and monitoring. All necessary instruments for control and monitoring of the plants shall be furnished and commissioned in each plant system. Instrumentation shall be provided but not limited to the following systems:-

Governor and MIV systems

Excitation system.

Plant Bearings.

Cooling water system

Dam and tail race level measurement

Generator temperature monitoring

Dewatering and drainage system.

Portal valve 2.2. Governor and MIV systems The governor and MIV systems shall be supplied complete with sufficient control and monitoring instruments to make them full functioning systems. A minimum of the instruments defined in Annex 1 shall be furnished. The contractor may include any other Governor instruments he deems necessary for the safe operation of the plant. 2.3. Excitation system The excitation systems shall be supplied complete with sufficient control and monitoring instruments to make them full functioning systems. A minimum of the instruments defined in Annex 4 shall be furnished. The contractor may include any other excitation instruments he deems necessary for the safe operation of the plant. 2.4. Unit Bearings: Instruments shall be furnished for control and monitoring of the following bearing parameters:-

Bearing oil sump levels (Contacts for oil level low alarm and oil level too low trip and 4-20mA signal for real time monitoring). Dial gauge thermometers with contacts for alarm and trip shall be installed as a back-up temperature monitoring system. The contacts shall be wired to annunciate at both the unit control board (SCADA) and alarm panel mounted on the auxiliaries’ board.

All Bearing pads temperature measurement by use of PT100. Dial gauge thermometers with contacts for alarm and trip shall be installed as a back-up temperature monitoring system. The contacts shall be wired to annunciate at both the unit control board (SCADA) and alarm panel mounted on the auxiliaries’ board.

Oil temperature measurement by use of PT100. These shall be interfaced to the unit control PLC for temperature alarming and tripping. Alarm and trip set point screen/menu shall be provided in the SCADA for adjusting the alarm and trip levels of the RTDs. 2.5. Cooling water system:

The cooling water shall be supplied via two hydro-cyclones. One Hydro cyclone shall be connected to the Maragua River penstock while the other shall tap water from the Mathioya River. The outlet of the two hydro cyclones shall be interconnected via a common header where each unit shall draw its cooling water. Each unit shall have its cooling water drawn from the common header through hydraulically operated valves and isolating valves. The hydraulic valve shall be operated by use of the governor pressure. Correctly rated valves shall be used for open/close commands and mounted on the same valve block as the MIV control valves. Valve status indication robust limit switches shall be mounted on the cooling water valve and the contacts connected the common PLC and Auxiliaries board for control and indication. Other parameters shall be monitored by use of the following instruments:-

Water pressure before each hydro-cyclone.

Cooling water pressure for each unit. To be connected after the hydraulic operated valve.

Cooling water temperature (Both inlet and outlet). 2.6. Dam and tail race level measurement

Dam level and Tailrace level equipment shall be provided real time level monitoring. Preferably radar level measurement instruments shall be used. The contract shall install appropriate equipment to transmit the signals to the SCADA system for real time level monitoring. The level in the SCADA shall be calibrated in METERS ABOVE SEA LEVEL (mASL).

. The appropriate mounting positions shall be agreed with the client during the preliminary design stage of the project. 2.7. Generator temperature monitoring Appropriate four wire RTDs shall be installed in the generator stator winding, stator slots and stator core for real time generator temperature monitoring. These shall be interfaced to the unit control PLC for stator temperature alarming and tripping. Algorithms in the PLC program shall be made such that failure of one RTD does not trip the unit. However, the unit shall trip if temperatures rise in two or more RTDs beyond the trip set point. Alarm and trip set point screen/menu shall be provided in the SCADA for adjusting the alarm and trip levels of the RTDs. 2.8. Drainage and Dewatering system The drainage and dewatering system shall be rehabilitated by the client. The pumps shall draw power from the new 415Vac distribution board. A minimum of the following control facilities and instruments shall be provided under this contract:-

Local control board; this shall have a key operated selector switch for local/automatic selection. When the pumps are selected local; Control shall be via push buttons installed at this panel. When the control is selected to automatic, the pumps shall be controlled automatically by the level switches.

A selector switch shall also be provided for duty/standby changeover of the pumps.

A minimum of the following level switches shall be provided for control of these pumps:

Level, stop pumps. Level high, start duty pump. Level high, start standby pump. Level high, alarm Level too high, station shutdown.

Contacts of the level switches and selector switches shall also be interfaced to the SCADA system for monitoring the drainage pump scheme.

A radar level transducer shall be installed for real time level monitoring of the drainage scheme in the SCADA system. The level in the SCADA shall be calibrated in METERS ABOVE SEA LEVEL (mASL).

2.9. Control of portal valve A new hydraulically controlled portal valve shall be supplied and installed in this contract. The contractor shall provide a complete hydraulic system with a control board for operations of the portal valve and the associated by pass valve. The hydraulic and control board shall include pushbuttons for open/close of both the portal valve and bypass valve, status indication instruments, pressure indication instruments for both the pressure system and penstock, pumping units, control valves, oil sump tank, pressure relief valve etc. The closing of the valve shall be via a counterweight system. Pressure transducers shall be installed in both the downstream and upstream sides of the portal valve to interlock opening of the portal valve if the pressures are not balanced. Interlocking shall be made such that when a command is given to open the portal valve, the bypass valve opens first to balance the pressure on both sides of the penstock. The bypass shall then close when the portal valve is open. All necessary instruments shall be provided for the safe operation of the hydraulic system of the portal valve.

ANNEX 3:

1.1.1. UNIT CONTROL AND SCADA SYSTEM

1.2. General description:

The units shall have two modes of control namely; Manual control and automatic control.

The manual control facility for the units shall be achieved by running/controlling the systems from

their respective local panels. A systems auxiliaries control panel complete with push buttons for

start/stop, LED alarm fascia, synchronizing system etc shall be established and mounted next to

the Governor and excitation panel to facilitate full manual control of each unit.

The automatic control shall be achieved by running/controlling the respective unit systems via the

unit control board PLC.

The new Wanjii automatic Control system shall be PLC based. Each unit shall be controlled and

monitored via a dedicated unit PLC. All common auxiliary systems/equipment shall be controlled

and monitored via a separate PLC (Common PLC). Each PLC and associated devices (I/O cards,

power supplies, control relays etc) shall be housed in a dedicated panel of rittal standard referred

to here as Unit control board (UCB).

The unit Control boards shall be hardwired to interface to the field equipment (sensors,

transducers, limit switches, turbine governor, excitation etc).

The unit control board (PLC) shall have three levels of control, namely:-

A. Local control: This shall be control of the unit via a touch screen industrial PC mounted on

the unit control board (panel). Each dedicated touch screen industrial PC shall

communicate directly to its associated unit PLC.

B. Local control centre: This shall be control of all the units at the common local control centre

described elsewhere in this document. A client-server control system shall be established

with redundant communication network to make a complete control system. Appropriate

HMI control software approved by the client shall be used.

C. Remote control centre: Connect to Kamburu remote control centre (KRCC) and KenGen

Central dispatch Centre (KCDC) as described in 1.3.3.

1.3. Unit Control Board:

Each unit shall have a dedicated unit control board. The unit PLC and associated devices (I/O cards,

power supplies, control relays etc) shall be housed in this panel.

The unit control board shall be interfaced to dedicated unit systems (excitation, Governor, GCB,

etc) through hard wired control logics. The PLC shall be the central control system of each unit

control board.

1.3.1. Unit PLC

A complete proprietary PLC system shall be supplied for each unit. This shall include CPU,

communication cards, power supply cards, input/output cards, network cards etc.

A signal list of all the interface signals (I/O) to the unit PLCs shall be developed and approved by

the client. Each signal shall have a unique signal tag number description that shall be used to

identify the particular signals in the drawings.

All the control logics of the unit shall be via the PLC. Appropriate PLC algorithm logics shall be

programmed in the PLC by use of high level PLC programming language to make safe control logics

for each unit. The PLC control logics shall include the following.

Step by step control of the unit from standstill to grid.

Automatic start/stop of the unit to the following steady state conditions/modes:-

Standstill to rolling mode

Standstill to excited mode

Standstill to grid mode

Grid to excited mode

Grid to rolling mode

Grid to standstill mode

The PLC shall be interfaced to the HMI control system via a dual, redundant communication

network. (See description of control system).

1.3.2. Power Supplies:

Each unit control board shall be equipped with dedicated power supplies for control and

monitoring circuits.

The Control voltage of each unit shall be 24Vdc. Dual redundant power supplies shall be provided

and shall draw power from both DC and AC sources as follows:-

DC supply -110 Volts

AC supply - 240 Volts

Failure of one source of supply shall not affect the operation of the unit. An output contact

indicating failure of any of the power source shall be provided. The primary and secondary

voltages of the power supply shall be galvanically isolated.

For lighting and heating of the cubicle 240Vac 50 Hz supply will be used. Cubicle lighting shall

be controlled by a door switch.

1.3.3. Control levels:

It shall be possible to operate each unit in the following control levels:-

A. Local automatic control: This shall be control of the unit via a tough screen industrial PC

mounted on the unit control board (panel). Each dedicated tough screen industrial PC shall

communicate directly to its associated unit PLC.

B. Local control centre: This shall be control of all the units at the common local control centre.

A client-server control system shall be established with dual, redundant communication

network to make a complete control system. Appropriate HMI control software approved

by the client shall be used.

C. Remote control centre: Connect to Kamburu remote control centre (KRCC) and KenGen

Central dispatch Centre (KCDC).

Remote Operation:

a) Background

KenGen is in the process of establishing a country wide SCADA system that enables monitoring and control of each of KenGen’s power stations from a central control room. The project will comprise a central dispatch centre and a number of regional control centres, interfaces to some twenty power plants (Upgraded Wanjii Power Station being one of the power plant) and a communications network linking power plants to control centres.

It is anticipated that the new upgraded Wanjii power plant shall be interfaced to Kamburu control centre (KRCC) and KenGen central dispatch centre (KCDC).

International standard interfaces and communication protocols will be employed to link the power

plant DCS’s to the SCADA control centres via WAN communication links.

Scope of Supply

The scope of supply for the Wanjii power plant interface shall be 2 (Two) gateways to support 2 local communications node each expected to comprise provision of:-

A DCS gateway or RTU interfaced to the DCS LAN, supporting IEC 60870-5 -104 communications protocols (see attached generic interface diagram).

Additional functionality within the power plant DCS to support remote control of each generating unit from an AGC module in the SCADA master station at the KenGen Central Dispatch Centre (KCDC). This shall include facilities and functionality for:

Selecting each unit to operate under AGC and Control level selections

Processing set points or raise / lower signals for modifying unit operating points for

MW and MVAr,

Inputting permitted operating ranges for MW and MVAr and the maximum ramp rates

supported by each generating unit.

Forwarding plant analogue measurements, status, events and alarm information to the

SCADA system via the gateway.

Accepting control commands sent from the KenGen Central Dispatch Centre (KCDC).

The contractor shall configure the Unit Control PLC program to be able to accept control commands from these remote control stations.

Meter readings from fiscal energy meters associated with each generator via IEC 62056-21

protocol (Electricity metering - Data exchange for meter reading, tariff and load control -

Part 21: Direct local data exchange) and forwarding the data to the KenGen CDC.

Communication Node 1 is to KenGen CDC (Stima Plaza KenGen)

Communication Node 2 is to KenGen Regional Centre (Kamburu)

DCS PLCs

RTU

Fieldbus / IEC 104

Conversion

Local Plant User

Interface

Communications Node

Fieldbus

Communications

Media

--/~

--/~

48 V dc Power Supply

(if required)

Meter Reading IEC

62056 / IEC 104

Protocol Conversion

Energy

Meter

Generic interface diagram

Notes.

Distances from Wanjii to Stima Plaza (KCDC) is 70 km while that from Wanjii to Kamburu (KRCC) is approximately 100KM. Distance from KRCC to KCDC is approximately 120 km. The connection of Wanjii to KRCC is not in the Wanjii upgrading project scope.

D. Manual control: when the control level selector switch is in this position, control of the

units shall be achieved via the local control panels and auxiliaries control panel. However,

it shall be possible to view the plant parameters from the control system HMI screens.

A Key operated selector switch shall be installed in each UCB to change the level of control from

local control (Industrial PC) to local control centre (Operator station) and vice versa. This selector

switch shall also be used to turn the PLC out of service should the need arise to run the units

manually from the local panels.

A software button shall be established in the control screen to transfer control of the unit from the

Wanjii control centre to Tana control centre and vice versa.

1.3.4. SCADA system and Human machine interface (HMI):

A SCADA system control architecture shall be established for the control of the units through a

dual, redundant communication network.

This shall consist of the following:-

Hot standby server system.

Client Operator system PCs (OPS).

Communication network with appropriate switches.

Event log printer.

One coloured printer.

GPS time synchronizing clock connected to the PLCs, server work stations Industrial PCs

and the operator and stations.

The SCADA system shall have client-server communication architecture. The system servers shall

communicate to each PLC through modbus Ethernet communication protocol to receive and send

data while the touch screen industrial PCs shall communicate directly to the dedicated unit PLCs.

The server work stations at Wanjii shall communicate to both the operator stations at Wanjii

control and the server work stations at Tana control centre.

The Wanjii control centre shall have two operator stations. It shall be possible to control the units

from any of the operator stations.

Appropriate control and monitoring graphical screens shall be developed to the approval of the

client. Basically the control functions shall be limited to the main screen while the other

screens/windows shall contain monitoring data and set points for the various plant parameters.

An alarm management screen shall also be implemented.

The control centres at Wanjii control room and Tana shall be complete with appropriate control

room furniture, UPS power supply, UPS outlet sockets, net work switches and telephone systems

etc.

The control room furniture shall have necessary internal cable ducts for network, power and

telephone connections and appropriate facility for storing the operator stations.

The server stations, network switches and associated equipment shall be housed in one cabinet.

The SCADA servers shall be supplied together with additional memory for data archiving and

storage.

KenGen is planning to establish dispatch centres for its power generating plants across the country.

One such dispatch centre is Tana remote control centre. It is expected that all plants in upper Tana

(Wanjii is one of them) shall be remotely controlled from here. Similarly a central data repository

for all the plants shall also be maintained. In this case therefore Plant historical data shall be

maintained in Plant information server located here. This however is not in the Scope of Wanjii

rehabilitation project.

Considering that the Process LAN in Wanjii is client server based, an OPC server application shall

be installed in the redundant server nodes (collectors) and configured for failover. The interfacing,

testing and commissioning to the Plant information system servers at Tana shall be accomplished

in this project. If by the time this project is being commissioned, the Tana plant information servers

will not be ready for interfacing the employer shall provide an alternative Plant Information server

already running and maintained in one of the existing KenGen plants.

The successful bidder shall be required to customize daily report templates to be accessed through

the RTweparts in PI. These reports shall be of agreed analogue parameters where archived values

will be populated in the templates on half hour basis. Monthly reports for parameters such as

energy shall also be customized. The data/parameters to be transmitted shall be agreed upon

during implementation.

An appropriate and reliable communication system to Tana control centre shall be established and

commissioned to link the remote control centre and the local control centre. Control of the units

shall only be possible at the Tana control centre when the control level is selected to remote.

An output from the SCADA system shall be generated to energize the siren module mounted in the

auxiliaries’ panel whenever an alarm occurs in the SCADA system.

A typical communication shall be as shown in the Sketch to be provided below.

Interface to corporate WAN

This shall be done via the corporate Local Area Network (LAN at Wanjii. Appropriate network

security devices shall be provided and configured to ensure only authorized devices in the

corporate network shall access the process LAN at Wanjii power station. Details of devices that

shall be granted access to the process LAN shall be provided during configuration of the network

security devices.

1.4. Auxiliaries control board:

An auxiliaries’ control panel shall be established and mounted next to the Governor and Excitation

control panel.

This panel shall be used for the following functions:-

A. Start/stop of all unit auxiliaries.

B. Synchronizing the unit.

C. An LED based alarm fascia with alarm reset and acknowledgement buttons.

D. Indicating instruments for generator active power, reactive power, current and voltage.

1.4.1. Auxiliaries start/stop functions.

All the unit auxiliaries shall be controlled from this panel when the unit control board panel

control level is selected to manual control.

Push buttons with integrated status indication LEDs shall be mounted on this panel and interlocked

with manual level of control.

These auxiliaries include but not limited to the following:-

Cooling water valve(Open/Close)

Unit braking system (Apply/Release).

Governor pumps (Start/stop).

Guide vane locks (Apply/release).

Emergency push button.

1.4.2. Unit Synchronizing system:

The Plant synchronizing system shall be installed in this panel.

The synchronizing system shall consist of the following:-

A numerical based technology synchronizing relay with push buttons for ON/OFF

Commands and indication.

Synchro-check relay with inbuilt Synchroscope (with phase angle indicating LEDs).

Double voltage meter.

Double frequency meter.

Raise/Lower center zero control switch for governor control during synchronizing and

loading.

Raise/Lower center zero control switch for excitation control during synchronizing and

loading.

Selector switch for manual/automatic synchronization selection.

Discrepancy switch opening/closing the Generator circuit breaker (GCB).

When the unit is operating at manual control level of command, the synchronizing system shall

be controlled via the ON/OFF push buttons on the auxiliaries’ panel.

When the unit is operating from the unit control board (PLC), the synchronizing system shall be

switched ON by the PLC when the control sequence reaches the synchronizing stage. The PLC shall

switch OFF the synchronizing relay after the GCB is closed.

In the event that the synchronizing relay is faulty, the synchronizing shall be done manually using

the double frequency meter, double voltage meter and the Synchro-check relay. The GCB shall be

closed via the discrepancy control switch.

The numerical based synchronizing relay shall include all the functions required for exact and

reliable synchronizing including synchronizing detection, for generator breaker closing

command. The voltage matching function will control the generator voltage regulator while the

frequency and phase matching function will control the turbine governor.

The device shall be mounted on the front of the auxiliaries’ panel.

The device electronics shall be galvanically isolated from the inputs and outputs. The device shall also have an operating panel for local operation, maintenance and diagnostics. The operating panel shall consist of a display (preferably LCD), a keyboard which is access-protected and LED indicators for a few alarms and indications. Parameters and actual values shall be displayed on a PC via RS232 serial interface. The software tool shall be provided in a CD and shall also include the cable to a laptop PC.

The device shall have a feature for external instrument transformer amplitude compensation or

alternatively an internal phase shift compensation feature. A test mode feature is required. Auto

shut off function feature after synchronizing and issue of breaker closing command is required.

The device shall have comprehensive self-monitoring functions consisting of at least: -

Periodical checks of A/D transducers

Monitoring of set point

Supply voltage

Memory

Parameters etc

To ensure maximum safety of the generator and network, while synchronizing, a synchro-check

relay shall be provided as an interlock in series. The scheme shall have a feature ‘dead bus’

paralleling to be used while running the unit on black start sequence.

A suitable PC based software tool for commissioning of the devices shall be provided.

1.4.3. LED based alarm fascia:

An LED based alarm/trips fascia shall be installed on the side of this panel for annunciating any

plant anomaly. This shall consist of grouped alarms from all the dedicated unit systems.

Alarms from the same system/function may be grouped together where applicable. The

alarm/warning LEDs shall be yellow in colour and flashing. The LEDs for trip indication shall be

red in colour and also flashing.

All the alarms and trips shall be annunciated via an approved siren module mounted on top of the

auxiliaries’ panel. The siren module shall consist of the following:-

Siren: To energize when an alarm/trip occurs.

Red light: for indication when an alarm/trip occurs.

Green Light: To indicate when the unit is running.

Amber light: To indicate when the unit is on standstill.

An output from the SCADA system shall be generated to energize the siren whenever an alarm

occurs in the SCADA system.

A minimum of 50 LEDs shall be used for grouped alarms and trips indication. Where one system

has several alarms, these shall be grouped together in several LEDs.

1.4.4. Indicating instruments:

Indicating instruments shall be mounted on the auxiliaries’ panel with correct units of measure

for the following functions:-

Generator active power.

Generator reactive power.

Generator currents single phase indication.

Generator voltage (three phase indication with line to line selector switch).

Cooling water pressure.

These instruments shall have a red mark inscribed at nominal values on each meter.

1.4.5. Control Panel Construction:

The control cubicles shall be of rittal standard, floor-mounted and free standing construction for

indoor installation with cable entry from the bottom. Ventilation points shall be provided with

suitable removable air filters to prevent the ingress of dust and insects. Cooling air fans shall be

incorporated in the panels.

Cubicle size and colour shall match the Unit Control cubicles.

The control cubicles shall be of tropical design and to IP54 Protection code of practice according

to IEC529.

The cubicle shall be fitted with lifting eye bolts which shall be removed after installation.

All metal parts other than those forming part of an electrical circuit shall be connected in an

approved manner to separate earth bars running along the bottom of the panel. The metal cases of

all instruments and the like shall be connected to the copper earth bars by conductors of not less

than 2.5sq mm or by other approved means.

Doors shall be fitted with handles and locks [key operated]. The cubicle shall contain internal

power sockets. Door operated cubicle internal lighting shall be provided.

All instrument and control devices shall be easily accessible and capable of being removed from

the panel for maintenance purposes. Labels permanently attached to the panel shall identify each

relay and electronic card within the panel and adjacent to the equipment concerned.

All control relays shall be robust and firmly supported on their bases by use of retainer clips or

springs to avoid looseness that may occur due to vibration.

The cubicle shall be made of sheet steel not less than 2.0mm thick.

Devices and component shall be mounted and labeled according to number and function.

The control cubicles shall have terminal blocks for reception of cables cores (2.5 mm2) for

interfacing to the other plant control equipment. All wiring shall be of adequate cross section area

to carry prospective short circuit without risk of damage to conductors, insulation or joints. Wiring

shall be supported using an insulated system, which allows easy access for faults finding and

facilitate the installation of additional wiring. Ribbon cables cables with plug and sockets

connectors may be used for light current wiring. Plug and socket connector shall be polarized so

that they can be inserted into one another in the correct manner. All wiring shall be identified in

accordance with the associated schematic and/or wiring diagrams by means of discrete wire

numbers.

All internal electrical wiring for the control panels shall be neatly terminated. All wiring shall be

insulated with 600-volt grade oil-proof material. All connections shall be made at terminal blocks.

Terminal blocks shall be provided and rated not less than 600-volt, and shall be provided with

covers. At least 10 per cent extra terminals shall be provided in each group or terminal blocks.

Permanent identification of all terminals wires shall be provided.

A consistent system of wire numbering approved by the client shall be used throughout the

equipment.

1.4.6. Training:

A comprehensive training on the control system, operating software and control PLC algorithms

shall be conducted by the contractor to client Engineers to equip them with sufficient knowledge

on how to maintain and carry out future modifications on the control and SCADA systems. This

shall be done before the commencement of the factory acceptance tests.

A five (5) Tier training program is recommended as follows to help in attaining full technology

transfer to client Engineers:

f) Basic Training prior to project programs development to absorb the software general

concepts

g) Participation in project programs development during design(attachment to Contractor)

h) FAT participation testing

i) Participation in commissioning of the project program (attachment to Contractor)

j) Site training in the configured project programs

The contractor shall present a training proposal that shall be discussed and agreed upon with the

client during the preliminary design

A Typical arrangement of the panels is as in a sketch to be provided during the site visits.

2. Communication Link between Wanjii Control Room and Tana Control Room.

The contractor shall establish a microwave point-to-point radio link between Wanjii Control room

and Tana Control room as specified below.

2.1. KenGen scope

KenGen shall avail existing communication masts at Wanjii Power Station and at Tana Power

Station for use by the contractor. The contractor shall establish, install and mount the necessary

equipment to share the mast with the existing equipment without interference. KenGen shall

provide power (AC) up to a distribution point, from where the contractor is expected to draw the

power for his equipment.

2.2. Microwave Point-to-Point Link

The contractor shall design, supply, install, test and commission a microwave point-to-point radio

link between the communication masts at Wanjii and Tana Power Stations. The masts are in use

by KenGen and the contractor must ensure that the equipment supplied and installed does not

interfere with any existing equipment or network.

There is a clear Line-Of-Site between the two stations.

The link shall be established on microwave frequencies in the 1.5GHz band. KenGen is utilizing

frequencies in the same band on the Kiritiri-Tana radio link and shall be responsible for payment

of the license fee to the Communications Commission of Kenya (CCK). The equipment supplied

must be robust to withstand the weather conditions in these locations. The preferred radio

equipment is Type Aprisa XE (or the latest model of the same) manufactured by 4RF

Communications Ltd of New Zealand.

The Specifications and configurations of the radios shall be as detailed in the table below.

3. Parameter 4. Requirement

Type & Model Aprisa XE complete with Monitored Hot standby

Switch (MHSB) per pair.

Configuration Hot standby Redundancy (1+1)

Power Consumption Max 180Watts

Nominal voltage -48Vdc, 4Amps

Input voltage range 40 to 60VDC

Channel Size 1.75MHz

Modulation QPSK, 16QAM,32QAM,64QAM,128QAM

Frequency Band 1400MHz (range 1400MHz to 1520MHz)

Environment Operating temperature up to 50° C

Humidity Maximum 95% non-condensing

Altitude Up to 2000 meters

Acoustic noise emission 59dBA (A-weighted sound

power level)

Mechanical Height ≤8U

Width: 19-inch rack mount

ETSI Performance Radio: EN 301 751, EN 300 630, EN 302 217 parts

1,2.1 and 2.2

EMI/EMC:EN 301 489 parts 1 & 4

Safety: EN 60950

Environmental: ETS 300 019 Class 3.2.

Interface Cards to be installed QJET Quad E1/T1 Interface (1No.)

DFXO Dual Foreign Exchange Office Interface

(1No.)

DFXS Dual Foreign Exchange Subscriber Interface (

1No.)

Ethernet Interface RJ-45x4 (Integrated 4-port switch)

Receive Sensitivity ETSI (for

16QAM Modulation)

-88dBM

Receiver Performance ETSI Maximum input level -20dBm

Dynamic Range 58 to 87 dB (at 10-6 BER) depending

on modulation type and channel size.

Carrier to Interference ratio (C/I ratio) at 16QAM:

better than 20dB

System Gain ETSI at 16QAM,

channel size 1.75MHz

119dB

Transmitter Power ETSI (16QAM

at 1400MHz frequency band)

17 to 31dBm

Antenna Connector N-Type female 50Ω

Configuration and Management Embedded web server and /or SNMP accessed via

Ethernet interface or across link.

Test points (for RSSI) Front panel test point for measuring the Received

Signal Strength Indicator (RSSI) voltage

The capacity of the link shall be 4E1s (approximately 8MBPS).

Power supply equipment for the radios at Wanjii and Tana shall comprise a 48Vdc, 30A redundant

19” Rack mount charger and Four (4 No.) 150Ah sealed re-chargeable batteries per site installed

in the same cabinet as the radios.

4.1. Last Mile Connection

The contractor shall lay optic fibre cable from the masts to the respective control rooms. The OFC

shall run in the ducting as a single run without jointing. The contractor shall lay a suitable ducting

on the ground running from the masts to the respective control rooms. The depth of laying the

ducting shall be suitable to avoid any damage and shall be approved by the employer. The route of

installation shall be clearly marked with concrete slabs suitably marked to indicate presence of an

underground cable. Inspection man-holes shall be placed along the ducting at distances of less

than 50m apart. The estimated length between the masts and the control rooms is:

Wanjii Mast to Control Room – 700m

Tana Mast to Control Room – 1000m.

Suitable media converters shall be installed to facilitate the last mile connection using the optical

fiber cable medium.

At the control room, the terminal equipment shall include a router configured with appropriate

interfaces, but at the minimum-Four (4 No.) T1/E1 and Two (2No.) 1Gigabit Ethernet interfaces.

The router shall be of Type Cisco 2900 series or the latest equivalent Cisco Router.

Ethernet switches supplied under this contract shall also be CISCO type. Their duty cycle shall be

industry rated so at to cope with the expected duty rate at site.

4.2. Communications Equipment Room at Wanjii

Communications equipment room at Wanjii, shall be provided by the employer.

4.3. Training on Telecoms system

A comprehensive training on the Telecoms system shall be conducted by the contractor to client

Engineers to equip them with sufficient knowledge on how to maintain and carry out future

modifications on the system. This shall take not less than Five days and shall be done before the

commencement of the factory acceptance tests.

The contractor shall present a training proposal that shall be discussed and agreed upon with the

client during the preliminary design.

Two (2No.) Engineers/Technicians are proposed for the training.

5. Tests and Commissioning

5.1. Factory Acceptance Tests

All components and assemblies of control & communications systems shall be tested in

accordance with the relevant IEC Standards to verify compliance with the requirements of

the Standards and Specification.

The control and protection systems shall have functional tests, signal checks and

redundancy systems failover tests shall be carried out at the factory before dispatch to prove

that all components operate together as a system and that all operating sequences and device

responses are satisfactory. It shall be the responsibility of the Contractor to provide test boxes

and other test equipment for sufficiently comprehensive tests.

All cubicles shall be subject to inspection during manufacture and on completion to verify

compliance with all the requirements of the Specification, including surface finish and

insulation resistance.

The client shall witness the factory tests.

5.2. Tests on Completion

General

The Contractor’s test schedules shall include comprehensive check lists for testing of the control,

protection, alarm and indication facilities.

5.2.1. Preliminary Tests

The preliminary tests shall include the following:

(a) Insulation resistance measurements at the specified voltages appropriate to the circuits and

equipment.

(b) Signal Test: Proof of correct connection and continuity of wiring for all control, protection,

auxiliary and alarm equipment in accordance with the overall diagrams as provided by the

Contractor.

(c) Functional tests to prove that all components operate together as a system and that all

operating sequences and device responses are satisfactory. It shall be the responsibility of the

Contractor to provide test programmes, test boxes and other test equipment for sufficiently

comprehensive tests.

(d) Tests of all indications, displayed quantities and analogue outputs to show such items

are within the accuracy limits specified.

5.2.2. Commissioning

Commissioning shall include the following:

(a) Demonstration that all controls, alarms and indications, including all sequences, displays and

reports operate correctly.

(b) A total of 50 starting, mode change and stopping sequences covering all the sequences to be

provided. During the specified 50 sequences required to be performed by each of the Units,

the whole of the equipment shall perform without adjustment.

(c) Sequence failure tests shall be carried out for each step in both start up and stopping

sequence.

(d) Remote monitoring and control of all Wanjii power plants and associated works from Tana

power station Control Centre.

(e) The Reliability Test Period.

ANNEX 4: - EXCITATION SYSTEM 1. Technical Specifications: Static Excitation Systems

1.1. Type and description. The Excitation equipment shall be designed to ensure continuity of operation under all working conditions and to facilitate inspection, maintenance and repairs. All reasonable precautions shall be taken in the design of equipment to ensure safety of personnel concerned with the operation and maintenance of the equipment. All electrical components shall be adequately rated for their most onerous duty and the specified ambient temperature. Due account shall be taken of any heat generated by the equipment therein and the components shall be appropriately selected, rated as necessary to suit the most onerous operating temperature within the panel.

The contractor shall design and supply a Static excitation system with excitation transformer. This comprises but not limited to:-

Excitation control

Automatic Voltage Regulator with adjustable PID controller (Automatic mode).

Dual Thyristor converter bridges in hot standby operating mode

Field suppression equipment

Rotor overvoltage protection equipment

Thyristor overvoltage protection

Static Excitation protection equipment

Under-excitation and Over-excitation limiters

Reactive Power influence (droop or compensation)

Rotor earth-fault protection (alarm and trip stages)

Field breaker

field flashing breaker

Voltage matching function

Excitation transformer overcurrent protection relay (alarm and trip stages)and any other protection system

Excitation Transformer and associated equipment. The control and instrumentation system shall include but not limited to:-

Interfaces with other control equipment (i.e. turbine, generator etc)

local instruments for monitoring excitation system and excitation transformer parameters

Interfaces with the protection equipment

Devices/relays required for the tripping of the excitation system

Hardwired manual controls; push buttons with integral lights, control relays, selector switches, timers, raise/lower switches, discrepancy switches, etc.

Connection of all unit control and instrumentation equipment/devices provided to the new excitation system with excitation transformer Panels.

Power, voltage and current Transducers

All additional items required for the safe and efficient operation of the excitation system.

1.2. Field flashing A field flashing system shall be included in the excitation system. This shall draw power from the 110Vdc battery bank being supplied under this contract.. A suitably rated MCB for switching the above mentioned supply for field flashing shall be provided in the excitation equipment. The circuit shall be designed to supply about 20% of the no-load field current. 1.3. Cooling air system Forced cooling of the Thyristor Convertor should be provided by AC driven motor fans, monitored by an air-flow relay. One AC- motor shall be provided for each of the Thyristor bridges. Thyristor heat sinks should be arranged to form a central duct through which the cooling air may pass leaving all of the small components and electrical insulation in relatively still air and less prone to the accumulation of dust. Suitable removable air intake filters shall be included on the cubicle housing the Thyristor converters. The fans shall be powered by the excitation transformer (main supply) and station auxiliary supply through a selector switch. The station auxiliary supply shall only be used in testing the fans under static conditions. The fans shall be protected by use of well rated MCCBs. The fans control shall be designed to run automatically with execution of excitation command. The fans should also have a manual mode, whereby the fans ON/OFF commands shall be initiated from both push buttons (with LED indications) mounted on the excitation panel and on the HMI. 1.4. Thyristor rectifiers The Thyristor converter shall consist of dual Thyristor bridges. The bridges shall operate in hot standby mode. Design and construction of the two bridges shall allow fault finding, maintenance and testing to proceed on one rectifier while the other remains in operation (online). The design shall satisfy all required operating conditions.

Failure in one rectifier shall generate an alarm and changeover to the standby but failure in both rectifiers shall result in a trip. The dual rectifier configuration shall ensure a smooth change – over from the main rectifier to the standby rectifier. The temperature of the thyristor converter shall be monitored by suitable resistance temperature detectors, mounted on the heat sinks. Temperature alarms shall be provided. The rectified bridge full load output shall be rated at a minimum of 1.2 times the maximum excitation current at ceiling excitation voltage. All equipment should be fully segregated by suitable insulation barriers to reduce the possibility of short circuits. An approved monitor/detector (conduction of current) circuit shall be fitted on each of the rectifier bridge to provide an alarm when the bridge fails. Should both bridges fail a trip command shall be issued. The alarm and trip shall be enunciated in the excitation system. Spare alarm and trip contacts shall be wired to the terminal block. DC millivolt ammeters driven by suitable shunts shall be provided to indicate the DC current from each rectifier bridge. These meters shall be mounted on the front of the cubicle housing the thyristor converters.

1.5. Excitation power supply: The excitation Control voltage shall be 24Vdc supply. Dual redundant power supplies shall be provided and shall draw power from both DC and AC sources as follows below:-

DC supply -110 Volts Nominal [Range +15 % /-20%]

AC supply - 240 Volts 50Hz Nominal [Range +5 % /-10%] Failure of one source of supply shall not affect the operation of the excitation equipment. An output contact indicating failure of any of the power source shall be provided. The primary and secondary voltages of the power supply shall be galvanically isolated. 1.6. Automatic voltage control(AVR) The automatic voltage control (AVR) shall be the normal mode of operation of the excitation system. The AVR shall include the following: The Control voltage of the AVR shall be drawn from the 24Vdc dual redundant power. Failure of one source of supply shall not affect the operation of the AVR equipment. An output contact indicating failure of any of the power source shall be provided. The AVR control algorithm shall have a PID response with two adjustable lead-lag filters to optimize the dynamic behaviour of the machine. Adjustable reactive and active power influence shall be implemented into the control algorithm to ensure stable parallel operation with the network and /or other generators. Any power supply failure or detectable component failure in the AVR shall result in automatic and instantaneous changeover to manual mode. The AVR shall include the following limiting functions:-

V/Hz – Limiter,

Maximum field current limiter,

Under-excitation P/Q – based limiter,

Stator current limiter,

Minimum field current limiter

Overvoltage limiter Field current limiter, instantaneously and delayed acting with an inverse time characteristic, shall be provided to protect the generator field against the excessive sustained output from the Excitation System. Stator current limiter, delayed acting with an inverse time characteristic in the overexcited and instantaneously acting in under-excitation operation mode, shall be provided in order to keep the stator current below a set value and prevents the stator windings from the thermal overloads. Minimum field current limiter shall act instantaneously and shall be provided to prevent overheating of the rotor.

All limiter functions should be integral part of the automatic voltage regulation program. They interact with the overall excitation control system in such a way that the operation of the generator is within its capacity limit. The generator terminal voltage shall be adjustable over the range of 90% to 110% of rated voltage under no-load operation. A reactive current compounding circuit shall be included to provide reactive load sharing during parallel operation. The compounding characteristic shall be adjustable. Low excitation or an MVAR limiter shall be included to prevent the regulator reducing the generator excitation below safe limits under loading power factor conditions. This equipment shall be arranged to provide an alarm and interlock in the event of extremely low excitation control. The voltage regulator shall be capable of controlling the field under the following conditions:-

Maintain generator voltage under normal operating conditions within 0.5% without hunting

Maintain generator voltage under load rejection or up to 150% over speed within 5% of its preset level.

Maintain generator voltage under maximum overspeed within 10% of its present level.

Continuous stable operation of the generator under line charging conditions Voltage control shall be accomplished by the continuous comparison of the average three phase voltage of the generator with a reliable and stable reference voltage source provided in the control system. A power system stabiliser shall be provided for protection against electromechanical oscillations from a system disturbance. The device shall operate to supplement the voltage regulating action by adding a controlled signal into the Excitation System input. The ratio of voltage to frequency limiting device with adjustable setter shall be provided to protect against over-excitation due to frequency drop. Provision shall be made for normal field de-energization with a crow bar and rapid field de-magnetization (via voltage inversion in a full thyristor bridge) whenever the generator lock-out relays/trip relays are operated or serious excitation faults occurs. The following monitoring and protection functions shall be integral part of AVR’s program:-

PT-failure monitoring,

Monitoring of synchronization voltages for control pulses,

Self test of electronics

Converter current monitoring 1.7. Manual voltage control(field current regulator (FCR)) The field current regulator (FCR) shall be provided to regulate the field current from about 20% of the rated generator terminal voltage to the rated voltage for generator operation at the rated output, rated power factor and rated frequency, and 110% of rated voltage. Provision in this mode shall be made to allow special tests namely:-

Excitation commissioning test- thyristor firing checks,

Generator open circuit and short circuit characteristic testing,

Generator Electrical Protection verification.

The manual control shall also incorporate EFCR (Emergency Field Current Regulation) mode

Maintenance purposes. A key operated selector switch shall be used to switch from AVR mode to manual mode and vice versa. However, if a fault occurs in the AVR during normal operating mode, the excitation shall switch over to manual mode automatically and generate an alarm to annunciate AVR trip to manual mode without tripping the unit. The manual mode (FCR) shall always follow the position of the AVR setting point. If a deviation occurs in the reference, an alarm shall be generated and annunciated in the unit control board. 1.8. Excitation control PLC The excitation interface to plant control and other systems shall be via a control PLC. All external commands from the automation system shall be connected to the control programmable logic controller (PLC) system. The excitation control PLC shall be interfaced to the AVR and other control devices in the excitation system. All the external commands and annunciation alarms between the excitation system and unit control PLC shall be via this PLC. Each Input/Output signal shall have a unique identification tag number and description. The excitation signal list showing the unique identification tag number and description shall be approved by the client. The excitation shall have two control levels. These are local and remote control levels. A key selector switch shall be installed to change from one level of control to the other.

Local control level: In this mode, the excitation shall be operated at the local excitation panel. Only commands from the excitation HMI panel or local push buttons shall be accepted.

Remote control level: In this mode, only commands from the unit control automation panel shall be accepted by the excitation system. However, trip signals shall not be interlocked through this selection.

The excitation Equipment shall be programmed by high level programming language that is user- friendly. Windows pull down menus and mouse control interface software shall be provided.

1.9. Supervision of excitation system Controller Comprehensive self testing and self diagnostic facilities are required to be included in the excitation equipment. The monitoring of the excitation system controller shall include but not limited to the following functions.

The Contractor shall provide details of the following facilities offered:-

Correct application program scanning check,

Memory integrity checks.

Validity of data exchange between memories, processing units and I/O modules.

Power supply check

Main processor unit status check,

I/O channel integrity check.

Error message display

Integral supervision functions

Other self test and diagnostic execution details.

Self monitoring of the processor

Process connections

The Contractor shall also provide details of the facility proposed for reporting the self test and diagnostic message. Output contacts shall be provided for external fault indication.

1.10. Voltage matching function/ Pre-synchronizing control. A Pre-synchronizing control system shall be provided. Using the grid voltage as a reference, it shall be designed to control the generator terminal voltage to a level equivalent to the grid voltage so that synchronization takes place smoothly. In the event that this system is faulty, the excitation shall be designed to build the generator terminal voltage to 11KV level. The excitation shall then receive commands for RAISE/LOWER from the synchronizing equipment to balance the generator terminal voltage to the grid voltage. 1.11. Peripherals and Software Package All peripherals to the excitation Equipment, such as programming units shall be supplied as part of this contract. The programming unit shall operate at 240V, 50Hz. The software package with the necessary license and the programs for all the PLCs, HMI used in the excitation system and the relay software used shall be supplied as part of this contract. The Contractor shall provide details of the facilities to be included. This shall cover the method of programming program storage, program loading and program documentation. Any modifications to an existing program shall be protected by password or key-switch security. The portable programming units shall be capable of providing the facilities for local excitation fault finding, self diagnostic facilities and commissioning. Details of the programming, de bugging, maintenance, fault finding and diagnostic facilities shall be provided by Contractor. . The software will display the signal values/level in the excitation on the screen of the portable device in an analogue manner. The software will provide functions to modify, store, compare the running program with file, test and for graphical documentation of the program.

A hardcopy of the software program including all the parameters setting and range shall be provided in the documentation. The operating software and the programs shall also be provided in a CD form for future loading into another PC. Cable and adapter interface required to connect the PC to the excitation equipment PLCs, HMI shall be supplied as part of this contract. 1.12. Training: A comprehensive training on the excitation, operating software and control PLC algorithms shall be conducted by the contractor to client Engineers to equip them with sufficient knowledge on how to maintain and carry out future modifications on the excitation system. A five (5) Tier training program is recommended as follows to help in attaining full technology transfer to client Engineers:

k) Basic Training prior to project programs development to absorb the software general concepts

l) Participation in project programs development during design(attachment to Contractor) m) FAT participation testing n) Participation in commissioning of the project program (attachment to Contractor) o) Site training in the configured project programs

The contractor shall present a training proposal that shall be discussed and agreed upon with the client during the preliminary design

1.13. Local Operator panel with HMI screens The local control of the excitation system shall be through an operator panel (shall be touch screen) industrial PC flush mounted on the excitation panel. This shall be via function keys on the industrial PC screen or control buttons developed on the industrial PC operator panel. The most important functions shall be placed directly at function keys, which should be common regardless of choice of window. Some of the function keys shall be used to set direct commands to process. Apart from the function keys being provided for in the operator panel, specific selector switches and push buttons mentioned in this document shall be provided to make the system operational in case the operator panel is faulty. The screens that shall form part of the requirement to interface and display field data are but not limited to: -

Main page: This screen shall contain the generator line diagram with animated symbols for the field breaker, generator breaker and the common bus bar. It shall also indicate day, date, time and the unit number and shall be used to log into the system through a password.

Operational data: This screen shall contain most important measurements, operational mode and set points for all different states.

Trends screen: In this screen, the operator shall be able to carry out a real time trending of line graphs of all the analogue signals.

Excitation Limiter list: This screen shall contain all the excitation limiters together with their set points.

Temperatures screen: All excitation system and excitation transformer temperature measurement shall be displayed on this screen.

Alarm list: All the alarms shall be indicated in this screen. Alarms/warning shall be flashing and yellow in colour while active trip signals shall be red in colour and flashing. Alarms/warnings that have normalized shall turn into green colour awaiting acknowledgement. This screen should also contain a button for alarm/trip acknowledgement and alarm reset.

It shall be possible to filter the alarm and trip list with date and time. The alarm/trip list shall be time stamped by the PLC and shall appear in a chronological order as they occurred. Each alarm shall have an identification tag number, the alarm description, time and date of occurrence.

Event logs: This screen shall contain all system events including alarms and trip signals. These shall be time stamped in the order of occurrence. It shall be possible to filter the event list with date and time. The event list shall be time stamped by the PLC and shall appear in a chronological order as they occurred. Each event shall have an identification tag number, the alarm description, time and date of occurrence.

Parameter display on all Human Machine Interfaces: All analogue parameters associated with the excitation system and the generator parameters displayed on all the excitation system HMIs shall be displayed in their respective units of measure.

1.14. Excitation system protection: The protection and alarms shall be provided for, but not limited to the followings conditions:- 1) PROTECTION/trip signals:-

Overcurrent, short circuit

Field flashing ,failure

Generator speed, low

Rotor overvoltage

Excitation transformer over temperature

Rotor earth fault stage 2, impedance less than 5K Ohms to ground

Loss of excitation

Two (2) or more rectifier protection fuses, blown

Failure of both rectifiers.

Failure of both power supplies.

Rectifier cooling failure These signals shall be interfaced to trip/shutdown unit via the unit control board.

2) ALARMS/warnings:-

One (1) rectifier protection fuse, blown

Voltage setter for AVR, fault

Voltage setter for FCR fault

Excitation transformer temperature high

Over-excitation limiter operated

Under-excitation limiter, operated

Volts per hertz limiter

Power system stabilizer, fault

Automatic reactive power regulator fault

Rotor Earth fault stage 1 , impedance less than 80K Ohms to ground

Generator actual voltage (Voltage from generator voltage transformer) failure

Rotor Overvoltage

110Vdc Auxiliary supply failure

AC supply failure

Voltage supply supervision: Excitation transformer temperature protection.

Thyristor converter temperature high

Change over to manual mode (Automatic mode failure) Fault

1.15. Rotor ground fault protection device An Approved active rotor insulation monitor devices shall be provided to indicate the active insulation level, to provide an alarm level (<80K ohms) and trip level (less than 5K ohms). Provision shall be made for isolation of the rotor insulation monitor device during maintenance of main rotor circuit.

1.16. Parallel operation and isolated operation. The excitation system shall be capable of supporting the unit while operating in both parallel mode (synchronized) and in isolated mode (unit not synchronized but running to supply local loads). 1.17. Panel construction The Excitation system with excitation transformer Panels shall be of rittal standard, floor-mounted and free standing construction for indoor installation with cable entry from the bottom. Ventilation points shall be provided with suitable removable air filters to prevent the ingress of dust and insects. Cubicle size and colour shall match the Unit Control cubicles. The excitation cubicle shall be of tropical design and to IP54 Protection code of practice according to IEC529. The cubicle shall be fitted with lifting eye bolts which shall be removed after installation. All metal parts other than those forming part of an electrical circuit shall be connected in an approved manner to separate earth bars running along the bottom of the panel. The metal cases of

all instruments and the like shall be connected to the copper earth bars by conductors of not less than 2.5sq mm or by other approved means. Doors shall be fitted with handles and locks [key operated]. The cubicle shall contain internal power sockets. Door operated cubicle internal lighting shall be provided. All instrument and control devices shall be easily accessible and capable of being removed from the panel for maintenance purposes. Labels permanently attached to the panel shall identify each relay and electronic card within the panel and adjacent to the equipment concerned. All control relays shall be robust and firmly supported on their bases by use of retainer clips or springs to avoid looseness that may occur due to vibration. The cubicle shall be made of sheet steel not less than 2.0mm thick. Devices and component shall be mounted and labelled according to number and function. The excitation Equipment cubicle shall have terminal blocks for reception of cables cores (2.5 mm2) for interfacing to the other plant control equipment. All wiring shall be of adequate cross section area to carry prospective short circuit without risk of damage to conductors, insulation or joints. Wiring shall be supported using an insulated system, which allows easy access for faults finding and facilitate the installation of additional wiring. Ribbon cables with plug and sockets connectors may be used for light current wiring. Plug and socket connector shall be polarized so that they can be inserted into one another in the correct manner. All wiring shall be identified in accordance with the associated schematic and/or wiring diagrams by means of discrete wire numbers. All internal electrical wiring for the excitation cabinet shall be neatly terminated. All wiring shall be insulated with 600-volt grade oil-proof material. All connections shall be made at terminal blocks. Terminal blocks shall be provided and rated not less than 600-volt, and shall be provided with covers. At least 10 per cent extra terminals shall be provided in each group or terminal blocks. Permanent identification of all terminals wires shall be provided. A consistent system of wire numbering approved by the client shall be used throughout the equipment

1.18. Cables and cabling works The contractor shall interface the excitation system via hard wired connections to the unit control board to be supplied under this contract. All the cables shall be of stranded copper cores, shielded and steel armoured. Cables shall be well labelled at both ends. All necessary cable support systems shall be provided. The contractor shall provide all necessary materials required for theses works.

1.19. Inspection and testing 1.19.1. Factory Tests

All components and assemblies of Excitation system with excitation transformer shall be tested in accordance with the relevant IEC Standards to verify compliance with the requirements of the Standards and Specification.

The client shall witness the factory tests.

The factory tests for the Excitation system with excitation transformer shall have but not limited to: functional tests, alarm test, converter firing tests, different modes regulation tests, no-load & load condition tests, limiters tests carried out at the factory before dispatch to prove that all components operate together as a system and that all operating sequences and device responses are satisfactory. It shall be the responsibility of the Contractor to provide test boxes and other test equipment for sufficiently comprehensive tests. All cubicles shall be subject to inspection during manufacture and on completion to verify compliance with all the requirements of the Specification, including surface finish and insulation resistance. The contractor shall submit a detailed factory acceptance tests program indicating all the tests that shall be carried out to the client for review and approval.

1.19.2. Site Tests

The Contractor’s test schedules shall include comprehensive check lists for testing of the operation, alarms and indication facilities.

The preliminary tests shall include but not limited to the following:

Insulation resistance measurements at the specified voltages appropriate to the circuits and equipment.

Signal Test: Proof of correct connection and continuity of wiring for all control, protection and alarm equipment in accordance with the overall diagrams as provided by the Contractor.

Functional tests to prove that all components operate together as a system and that all operating sequences and device responses are satisfactory. It shall be the responsibility of the Contractor to provide test programme and test equipment for sufficiently comprehensive tests.

Tests of all indications, displayed quantities and analogue outputs to show such items are within the accuracy limits specified.

Transformer tests: Insulation resistance measurements, vector group, ratio test, protection tests etc.

The Tests on Completion shall include the following:-

Demonstration that all controls, alarms and indications operate correctly.

operating Modes change

AVR changeover to manual

Rectifier changeover

Demonstration that all Emergency stops and Shutdown (both excitation external and internal Trips) controls operate correctly.

The Reliability Test.

1.20. Excitation spares spare parts

The contractor shall provide but not limited to the following spare parts. The contractor shall supply any other spare part that may be considered useful due to his design.

20% of each type of control relay

20% of each bi-stable relay

20% of each type of control timer relay

Four trip relay of each type

Four indicating instrument of each type

20% of indicating lamps (LEDs) of each type

Two power supplies of each type

Two power supply supervision relay of each type

four MCCBs of each type

Two Switches of each type (push-button, selector switch, discrepancy switch, key-switch, etc)

One Electric power transducer

One PLC CPU of each type loaded with the appropriate software and program

One HMI module of each type loaded with the appropriate software and program

One PLC input/output card of each type.

AVR cards. One per type

Excitation transformer temperature sensors (two)

Thyristor temperature sensors (two)

Eight thyristors

Ten thyristor fuses Note: Where percentages are used the fractions shall be rounded upwards. 2. EXCITATION TRANSFORMER

A three phase excitation transformer shall be supplied to step down the 11KV output of the generator voltage and feed the excitation rectifiers. The transformer shall be correctly rated to carry out maximum probable Excitation current required depending on the generator rating. The transformer shall be of the dry type, copper winding, suitable for indoor installation; manufactured in accordance with IEC 60076-11 wound for a primary voltage equivalent to the generator rated voltage and rated to suit the rectifier equipment. It shall be complete with all necessary cable boxes, primary current transformers, primary bushings, skid underbase, rating and diagram plates, lifting lugs and earthing terminal, all contained in sheet steel cubicle housing. Transportation rails shall be incorporated for the purpose of transporting the transformer to and from the mounting position.

The design of the transformer insulation throughout shall be suitably coordinated for the specific insulation level to minimize the effect of any impulse surge voltages.

The transformer shall be adequately protected against over current and temperature rise. The temperature of the transformer shall be monitored by use of both PT100 and a capillary dial gauge. The capillary dial gauge shall be flush mounted on the excitation panel to display the transformer temperature. This shall have heavy duty contacts with set levels for

alarm and trip signals. These contacts shall be enough for annunciation on the excitation alarm window. Spare alarm and trip contacts are to be provided and wired to the unit control board.

The PT100 temperature sensors shall be connected to the excitation PLC and unit control board system for real time temperature monitoring. The connection to the transformer shall be tapped from the outgoing generator terminals. The contractor shall supply and install connection cables/copper bars that are adequately rated and supported with insulating material. Current transformers for over current protection schemes shall be installed.

The excitation transformer and its auxiliary equipment shall be housed. The housing enclosure shall be well ventilated to allow maximum cooling of the transformer.

ANNEX 5- PROTECTION RELAYS AND 11KV INDOOR SWITCHBOARD

TECHNICAL SPECIFICATION: PROTECTION SYSTYEMS

1. General Specifications

The general specifications for the electrical protection systems are:

The protection relays shall be numerical relays based on microprocessor technology. The

relays supplied shall have fault recording facilities for use during analysis of system

disturbances. The relays should also have measurement facilities.

The relay programming & testing software and the fault analysis software shall be supplied

in a portable computer (laptop) and shall be handed over to the employer. Any additional

tools (e.g. communication cable) required for programming and testing of tall protection

relays , including the necessary licenses, shall also be supplied. The specific features of the

laptop shall be included in the tenderer’s bid and shall be subject to approval by the

employer.

The relays shall have an LCD display for display of measurements, settings, alarms and

trips. They shall also have LED indications which shall be configurable for annunciation.

The relays shall be supplied with 110VDC from the station batteries. The input and output

contacts shall be of robust construction to withstand harsh operation conditions. All trip

contacts shall be latched contacts.

The individual functions shall be hardwired to the unit PLC for generator related trips and

to the common plc for the generator transformer, station transformer and feeder related

trips. This shall be for purposes of annunciation. Additionally, a grouped alarm from each

protection relay shall be hardwired to Unit auxiliary panel for indication on the alarm

fascia.

The relays shall be flush mounted to the panels. There shall be test terminals blocks for use

in testing of the relays. Such test blocks shall isolate the field inputs and allow for testing of

the relays without isolation of wiring to the relays. Any accessories required for testing shall

be supplied together with the relays.

The protection relays for the generators and transformers shall be housed in a minimum of

two free standing panels. The actual relay and panel arrangement shall be approved by the

employer.

Feeder protection relays shall be located in one free standing panel. This shall include the

test terminal blocks and associated auxiliaries. A set of relay programming software, fault

analysis software, plugs for test terminal blocks and any related accessories necessary for

programming, testing and commissioning of feeder protection relay must be supplied, in

addition to the previous requirements. This set of kit shall be for use by the grid operator

(Kenya Power).

The contractor shall be responsible for determination of relay settings for generators,

generator transformers, station transformers and feeders’ protection. The contractor shall

provide the functions listed below as a minimum. Where the relay supplied contains more

functions than the list below, the contractor is expected to implement the extra functions

into the protection schemes.

The contractor shall also be responsible for review of relay setting at the end of the

transmission lines located at 11/33kV substation at Tana Power Station. Where such a

review may require additional features to the existing ones, the contractors shall advice the

client and supply accordingly at no extra cost to the client.

The trip matrix from the protection relays shall be coordinated to allow for fast clearance

of the faults with proper equipment/system isolation principles. Such a matrix shall be

provided for approval by employer.

The current transformers and voltage transformers to be used for protection have already

been specified in other sections of this document.

2. Generator Protection

The following generator protection functions shall be provided, preferably in one

multifunction protection relay,

o generator overvoltage

o generator under voltage

o generator over frequency

o generator under frequency

o instantaneous and time dependent over current

o 95% stator earth fault

o Generator reverse power

o Percentage Differential Protection

o Negative Phase Sequence

o Breaker Failure Protection

o Thermal Protection (Stator RTDs)

o Under Excitation

o Breaker Failure

o Trip circuit supervision

The over current protection of the excitation transformer shall also be provided as part

of the generator protection. The contractor may include the function as part of the

generator protection relay or may provide a relay for this function.

The relays shall have a minimum of three RTD inputs.

The following trip outputs shall be provided as a minimum:

o Governor Trip

o Excitation Trip

o Generator Circuit Breaker Trip

o Unit PLC.

o Bus coupler

3. Generator Transformer Protection

The following protection functions shall be provided

o Transformer differential

o Neutral Voltage Displacement

o Restricted Earth Fault

o Instantaneous Earth Fault

o Instantaneous and time dependent over current

o Voltage Controlled Over current

o Breaker Failure

o Over fluxing

o Trip circuit supervision

The following trips should also be provided for as inputs

o Winding and Oil Temperature Trips

o Pressure Relief Device Operated Trip

o Buchholz Gas Trip

The relays shall have a minimum of three RTD inputs.

The differential protection zone of the transformer shall cover the zone up to the high

voltage terminals of the station transformer.

The following trip outputs shall be provided as a minimum:

o Generator transformer Breaker (SF6 CB)

o Generator Circuit Breaker Trip to each generator

o Bus coupler trip

o Unit PLC.

4. Station Transformer Protection

The protection shall include the station transformer and the auxiliary feeder transformer.

The following functions shall be provided for

o Instantaneous and time dependent over current

o Instantaneous earth fault.

o Breaker failure

o Trip circuit supervision

The following trip outputs shall be provided as a minimum:

o Generator transformer Breaker (SF6 CB)

o Generator Circuit Breaker Trip to each generator

o Bus coupler trip

o Unit PLC.

5. Feeder Protection

Feeder protection shall be provided for the protection of Tana 1, Tana 2 and Mesco feeders.

The following functions shall be provided for:

o Instantaneous and time dependent over current

o Instantaneous earth fault

o Breaker Failure

o Trip circuit supervision

The following trip outputs shall be provided as a minimum:

o Generator transformer Breaker (SF6 CB)

o Feeder Breaker (SF6 CB)

6. Lock-Out Relays

There shall be lock-out relays for the generators, generator transformers, and the feeders.

These relays shall issue trips to the trip coils of the circuit breakers after receiving trips for

the control system and the protection relays.

The relays shall have a hand and automatic reset mechanism. They shall also have LED for

status indications.

The lock-out relays shall have a minimum of 10 heavy duty contacts.

7. 11KV Switchboard

There shall be a new switchboard established for the connection of the following:

o Four generator incomers

o Two transformer feeders

o One bus coupler

o One station transformer feeder specified under annex 6 clause 2.

The switchboard manufacture shall be in conformance to international standards, among

them IEC 60056, 60298, 60694 and 622271 (applicable parts). The design and

operational philosophy of the 11kV switchboard must be submitted for review and

approval by the employer before any assembly or manufacturing can commence.

The switchboard shall be in two sections, with laminated copper busbars of a nominal

rating of 11kV, 1250A (minimum), 3-phase and 50Hz. The busbar shall be rated to carry

the full load of the station without violating the temperature rise limitations of the

switchboard.

The contractor shall determine the short circuit current levels at the various points of the

system. The short circuit rating of the busbar and switchboard equipment shall be

coordinated with the determined short circuit levels.

Proper insulation coordination shall be done for all equipment installed in this project as

per IEC 60071-1 and IEC 60071-2.

The breakers supplied shall be vacuum circuit breakers (VCBs) rated at 11kV, 630A, 3-

phase 50Hz. The breakers shall be withdrawable for isolation purposes. The exposed busbar

should be covered with lockable safety shutters whenever the VCB is withdrawn. The

switchboard should have integral earthing on all the feeders that shall be applied whenever

needed.

The switchboard shall have provision for bottom entry of power and control cables.

Termination of the power and control cables shall be of good engineering workmanship.

All control cable terminations shall be placed in an easily accessible location, preferable in

the low voltage compartment of the panels. The contractor may consider establishing a

marshalling kiosk/panel where it is considered that the location of the terminations is not

safe enough for staff carrying out maintenance works.

The switchboard apparatus shall be supplied with 110VDC supply from the 110VDC

station batteries. Each circuit breaker shall have two trip coils with independent and

duplicated circuits and one close coil. There shall be trip circuit supervision of the breakers

achieved by use of protection relays.

Each incomer or feeder shall have voltage and current transformers for protection,

metering and instrumentation as may be required. The VTs for Neutral Voltage

Displacement (NVD) protection of the generator transformers shall be located on the

Transformer feeders before the respective breakers.

There shall be two busbar VTs – one on each bus-section. The VTs shall have two cores each

for synchronizing the generators to the bus-section.

The Voltage transformers (VTs) should be fixed with withdrawable fuses on the primary

and secondary voltage sides. The VTs shall be rated at class 3P, 11000/√3/110/√3 VAC,

50Hz and shall have the following cores:

o Metering core -Class 0.5

o Protection core – class 3P

The contractor shall determine the appropriate rating and specification of the Current

Transformers (CTs) to be mounted in this switchboard. The CTs shall have a minimum of

the following cores

o Metering and Indication – Class 0.5

o Differential Protection core for transformer or generator protection as appropriate.

o Over-current Protection core

There shall be local indication of one phase voltage and one phase current by use of analog

devices (of size 96 X 96 mm) on each incomer or feeder.

Indications that are local to the switchboard shall include

o ON, OFF, TRIP by use of LED lamps.

o ISOLATED, IN TEST and IN-SERVICE positions.

There shall be LOCAL/REMOTE selection switch to allow for remote closing of the breaker

via the SCADA/PLC system or from the Unit Auxiliary Panel.

Factory Acceptance Tests

Protection panels including relays, and metering equipment shall be subjected to

routine and type tests at the manufacturer’s works in accordance with the relevant

International Electrotechnical Commission (IEC) Standards or equivalent.

All protection relays and associated equipment shall be tested in accordance with the

requirements of IEC 60255.

Type test reports shall be accepted in lieu of type testing; provided that the

Contractor submits in advance, certified type test reports for tests on similar

equipment carried out by an independent accredited testing authority.

Tests on Completion

General

Test sets and test equipment required for testing the protection relays and metering

equipment shall be provided by the Contractor. All protection relays and associated

equipment shall be tested in accordance with the requirements of IEC 60255.

Site Tests

The following inspection and tests shall be carried out at site:

(a) Visual inspection

(b) Insulation resistance test

(c) Wiring checks and loop resistance

(d) CT polarity and magnetisation curves

(e) Secondary injection tests on protection relays

(f) Primary injection tests of relays and circuit wiring

(g) Alarm and trip testing

(h) On-load tests with simulation of faults

(i) Operation and accuracy of all meters shall be verified

ANNEX 6 –SWITCH YARD AND TRANSFORMERS

POWER EVACUATION FROM THE STATION.

The proposed single line diagram for the power flow is shown as drawing 1.

The power generated from the four generators shall be evacuated through Tana 1 and 2 feeders to

an 11/33kV substation located at Tana Power Station.

One generator on Mathioya River and one generator on the Maragua River shall be connected to

one section (section 1) of the 11kV Switchboard, while the remaining generators shall be

connected to the other section (Section 2) of the switchboard. There shall be a busbar coupler in

this switchboard which shall be designed as Normally Open circuit breaker. The switchboard shall

consist of vacuum breakers, current transformers, voltage transformers, earthing switches and

other associated equipment for the incomers and feeders.

The output of the generators shall be connected to the 11kV switchboard by use of XLPE cables.

From the switchboard, Section 1 shall be connected via XLPE cables to generator transformer 1

located in the switchyard. Section 2 of the switchboard shall be connected via XLPE cables to the

generator transformer 2 installed in the yard. The XLPE cables shall be terminated on the

transformer cable box. Each Transformer shall be sized for 2 Mathioya machines and one

Maragua machine.

The switchyard shall have two generator step-up transformers outdoor circuit breakers (SF6 type),

Disconnector switches (isolators), a bus-coupler connecting the two sections of the 11kV busbar

and a step-down transformer supplying auxiliaries board in the power house.

The power output from the two transformers shall be connected to an 11kV overhead busbar

serving Tana 1 and Tana 2 feeders. There shall be an isolator on this busbar which shall mainly be

operated in an open position. There shall be circuit breakers and isolators for the Tana 1 & 2

feeders. The contractors scope shall extend past the line breakers, isolators, VTs and CTs upto the

take off of the Tana 1 & 2 feeders.

On the star side of each transformer, there shall be overhead conductors connecting the

transformer to an overhead 11kV busbar via an outdoor SF6 breaker and an isolator.

The insulation level for all switchgear and equipment delivered under this project shall be guided by IEC 60071-1 and shall be as follows:

Nominal Voltage Rating of the

Equipment, Ur

11kV

Highest equipment voltage, Um 12kV

Standard Short-time power frequency withstand

voltage, RMS value

28kV

Standard lighting impulse withstand voltage,

peak value

75kV

1. GENERATOR TRANSFORMERS

The generator transformer shall conform fully to the requirements of IEC 60076

The transformers shall be outdoor type, three-phase, single unit oil-immersed step-up generator

transformer.

The transformer shall be suitable for continuous outdoor operation in tropical latitudes with the

following atmospheric conditions: Altitude: 1200m Above Sea level, Heavy humidity of up to

60% and Ambient temperatures 45°C max and 10°C min.

1.1 Rating

Transformers shall be rated as follows:-

Each Transformer shall be sized for 2 Mathioya machines and one Maragua machine. Each

section shall connect one machine from Mathioya river and one machine from Maragua river

with a bus coupler to connect the two sections.The generator transformers shall be rated for

50Hz, YNd1 vector group. The star winding shall have an On Load Tap changer with seven (7)

taps with a voltage variation of +/- 1.5% from nominal tap. The contractor shall determine the

nominal tap rating of the transformer taking into consideration the existing transmission lines

evacuating power from Wanjii. The impedance rating of the transformer shall be 10% and

within tolerances as specified in the IEC 60076 standard.”

1.2 Cooling system

The transformers shall have an Oil-Natural-Air-Forced cooling system. The cooling fans shall be

mounted on the transformer sides. The cooling systems shall be designed to ensure a maximum

temperature rise of 500C when operating at full load and normal ambient conditions. Contacts

of the winding temperature indicators shall be used to control the starting and stopping of the

fans. The fans shall be operated (on/off) at different temperatures. The necessary valves for

transformer bleeding shall be provided.

1.3 Tap changer

On-load tap changer shall be provided with a handle for manual operation. Tap position shall

be indicated on the tap changing mechanism and in the SCADA system. Completion of tap

changing process/cycle shall be monitored and indicated. The tap changers shall have both local

and remote operation facilities.

1.4 Bushings

Both HV and LV windings shall be brought out separately through bushings in accordance with

IEC 60137. HV bushings must be fitted with protective spark gaps.

The transformer shall have the following bushings: HV, HV neutral and LV bushings.

1.5 Current transformers

The neutral bushing shall be provided with current transformers for Restricted and

Instantaneous Earth fault protection of the transformer.

Each HV phase bushings shall be provided with the current transformers for differential and

over current protection of the transformer. The ratings of the turret CTs shall be suitable for

their protection functions.

The LV bushings shall be provided with the current transformers for winding temperature

indication.

The terminals for the bushing CTs shall be clearly marked and polarity indicated.

1.6 Transformer protection

Transformers shall have Buchholz relay, pressure relief device, oil level indication gauge,

winding temperature and oil temperature mercury thermometers with alarm and trip contacts.

The devices shall be wired to the marshalling kiosk. The above protection signals shall be hard

wired to the protection relay and to the common plc panel.

1.7 Conservator

The transformers shall be provided with a conservator for expansion of the oil which shall be

sized with due regard to the full range of climatic and operating conditions.

A dehydrating breather shall be fitted to each conservator. The conservators shall be fitted with

valves for draining and filling of the conservator.

1.8 Tank

The tank shall be of welded steel construction and shall be designed to withstand all stresses

which may occur in service, during transport and during oil treatment, including full vacuum

with radiators fitted. The transformer tank shall be fitted with valves for draining, filling and

filtration of the oil in the transformer.

1.9 Oil

Transformer oil shall also be supplied to fill the transformers delivered. The oil supplied shall be

mineral oil and shall comply with IEC 60296. 20% more oil shall be supplied in oil drums of

approximately 200 litres.

1.10 Core, winding construction

The core of the transformer shall be constructed of non-ageing cold rolled grain oriented low

carbon silicon steel. The maximum flux density at rated voltage and frequency shall not exceed

1.65 Tesla.

The windings shall be designed to withstand all dielectric, electromagnetic and thermal stresses

which might occur under the operating conditions including those produced by lightning

surges, short circuits, faulty synchronising and vibration. The windings shall also withstand

mechanical shocks originating from handling during transport and seismic disturbances.

1.11 Marshalling kiosk

Marshalling kiosk shall accommodate the following: - winding temperature indicator, oil

temperature indicator, circuit breakers and selector switches for fan control, terminal blocks for

wiring of field device. All the field devices shall be wired to the marshalling kiosk for connection

to the control room for indication, control and alarming purposes. The wiring inside the kiosk

shall be well labelled and laid in the trunkings in good workmanship.

2. AUXILIARY TRANSFORMER

The transformer shall be of the mineral oil immersed core type suitable for outdoor use with Oil

Natural Air Natural (ONAN) cooling.

Transformer supplied shall comply with IEC 60076

2.1 Rating

The transformer shall be rated at 11000V / 415V, Dyn11, 50Hz. The contractor shall determine

the power rating of the station transformer. The transformer rating shall be at least 20% more

than the determined load in the power house and auxiliary loads. The impedance rating of the

transformer shall be guided by the IEC 60076

2.2 Cooling system

The cooling systems shall be Oil Natural Air Natural (ONAN).

2.3 Tap changer

The transformer shall be provided with approved off circuit tap changing equipment.

2.4 Bushings

Both HV and LV windings shall be brought out separately through bushings in accordance with

IEC 60137. Alternatively, the LV bushings may be brought out through a cable box.

The transformer shall have the following bushings: HV, HV neutral and LV bushings. The HV

bushings must have protective spark gaps (arcing horns).

2.5 Insulating Oil

The transformer shall be filled with low viscosity mineral insulating oil, which in every respect

complies with the provision of IEC 60296.

2.6 Protection

Transformer shall have Buchholz relay, pressure relief device, oil level, winding temperature

and oil temperature mercury thermometers with alarm and trip contacts. The protection devices

and such other accessories shall be wired to the marshalling kiosk. The above protection signals

shall be hard wired to the protection relay and to the common plc panel.

2.7 Current Transformers

Current transformers shall be provided for the station transformer protection scheme. The

Current transformers shall comply with the requirements of IEC60044-1. They shall be class

0.5, with a secondary rating of 1A.

3. SWITCHYARD SWITCHGEAR

There shall be a substation whose proposed layout is shown in drawing 2. In the outdoor

substation, there shall be the following:

1. 11kV Isolators

2. 11kV SF6 Circuit Breakers

3. 11kV Overhead Busbar

4. 11/0.415kV Alternative Feeder Transformer

5. 11kV XLPE Power Cables

6. 11kv Surge Arresters

7. Tana 1 & 2 take-off

VERTICAL SWING SINGLE BREAK

3.1 11KV ISOLATORS/DISCONNECTOR SWITCHES

The isolators supplied shall conform to IEC 62271-102 and other recognized

international standards.

The disconnector switches /isolators shall be of the vertical swing, single-break type with

porcelain insulators. They shall be 3 phase, non-motorised with a provision for applying

padlocks for safety purposes. All apparatus required for manual operation of the

disconnector switch shall be supplied.

The operating mechanism shall be extended to a level appropriate for human operation.

The disconnector switches shall have integral earthing switches with the necessary safety

interlocks.

The operating mechanism, terminal blocks and cables shall be placed in a weatherproof

kiosk and mounted on the support structure and not directly below the busbars.

The indications for isolator OPEN or CLOSED shall be wired to the Common PLC for

indication purposes.

The contractor shall determine the current rating of the isolators suitable for operation

at nominal voltage rating of 11kV.

The isolator shall be designed for switching of transformer charging current and shall

have necessary interlocks with the circuit breaker to prevent its operation under load

conditions.

The moving and stationary contacts shall carry the rated load and short circuit currents

without welding and shall be approved by the employer before supply.

The isolators shall be supplied with galvanized steel structures for support. The safety

and working clearance shall be observed during the design of the structures.

3.2 11kV SF6 CIRCUIT BREAKERS

The breakers supplied shall conform to IEC 62271-100 and related standards.

The breakers shall be 3 phase breaker with a single operating mechanism. Such

mechanism shall have anti-pumping circuits, operation counter, local/remote selection

switch, breaker position auxiliary contacts and a power socket outlet.

The breaker shall be capable of carrying the rated and short circuit current without

damage to its contacts or arc quenching mechanism. It shall be capable of switching

magnetizing currents of the transformers, out-of-phase switching and short-line faults

that may occur in service.

The breaker shall have a motorized spring changing mechanism supplied by 110VDC.

There shall be provision for manual charging of the spring and the required apparatus

shall be supplied with the breakers.

The breakers shall have auto-reclosure and synchronizing facilities/features and

associate control circuits.

The breaker control and trip circuits shall be supplied with 110VDC from the station

batteries. Each breaker shall have two trip coils with independent but duplicate trip

circuits. There shall be breaker fail protection on these breakers.

The breaker shall have facilities to monitor SF6 gas levels and issue alarm and lock-out

breaker operation in case of a low and very low gas levels respectively. There shall be

provision for refilling of the gas.

There shall be local and remote indication of alarms. The local indications shall include:

Breaker ON/OFF/TRIP status, spring charge/discharge status, breaker Lock out. The

remote indications shall consist of the above alarms including the gas alarm and lock out

events, local/remote selector position. The remote indications shall be wired to the

common PLC.

The breakers operating mechanism, controls, terminal blocks, local indications and

cables shall be housed in weather-proof, vermin-proof enclosures and shall mounted on

the supporting structure of the breaker, preferably to the side of the busbars.

The supporting structure shall be made of galvanized steel and shall be designed with

consideration of safety and working clearances.

3.3 11kV OVERHEAD BUSBARS

The overhead busbar shall connect Tana Feeder 1 to Tana Feeder 2 via a disconnector

switch.

The disconnector switch shall conform to the specifications above.

The rating of the overhead busbar shall provide for transfer of power from either

generator transformer to any of the transmission line. This will provide the required

operational flexibility of the two lines.

The busbar shall be supported by well designed galvanized steel structures. Wooden

support structures shall not be allowed.

3.4 11/0.415KV ALTENATIVE FEEDER TRANSFORMER

The existing 11/0.415kV Station transformer shall be re-located to the outdoor

switchyard.

The high voltage shall be connected to the 11kV overhead busbar via a disconnector

switch. The overhead conductors and the disconnector switch shall be of a suitable rating.

The low voltage side shall be connected to the main 415VAC switchboard in the

powerhouse via power cables of a suitable rating.

The disconnector switch supplied shall comply with the specifications above.

Appropriate cable termination accessories shall be used to terminate the power cable on

both ends.

3.5 11KV XLPE POWER CABLES

The XLPE Cables and accessories supplied shall conform to the applicable standards

among them IEC 60183, 60502-2

The XLPE cables shall be used for the connection of the 11kV terminals of the generators

to the 11kV powerhouse switchboard and from this board to the generator transformer

cable boxes.

The cables shall be appropriately rated for evacuation of power from the two bus sections.

Linear Heat Detectors shall be laid on all the XLPE cables used for power evacuation.

These cables shall be laid as per applicable standards.

The cables shall be neatly laid in cable trenches on cable ladders and trays as is good

engineering workmanship. There shall be segregation of the various cable sizes and

rating.

3.6 SURGE DIVERTERS

There shall be surge diverters for the protection of the transformers. They shall be

installed on the high voltage side of the transformer.

The surge arresters shall comply with the requirements of IEC 60099-4.

They shall be of the metal-oxide type and shall be supplied with porcelain housings. The

surge arresters shall be provided with insulated bases, grading rings, foundation bolts

and supporting structures.

On each phase, the surge diverters shall have an operation counter and a leakage current

monitor. The leakage current shall be shown by use of a suitable scale. The scale for

leakage current shall have graduations to indicate alarm and trip levels

The surge arresters shall be fitted with suitable pressure relief devices to prevent the

porcelain shuttering in case of arrester failure.

3.7 TANA 1 & 2 FEEDER TAKE-OFF

The contractor shall supply, install, test and commission the line breakers, CTs and VTs,

disconnector switches with integral earth, post insulators and associated accessories for

each feeder.

The contractor shall establish the take-off gantry structure, string and terminate the

conductors on the existing feeders to the 11kV busbar.

The contractor shall as well establish the lightning arresters and protection for the

substation.

All substation structure shall be made of hot-dip galvanized steel to prevent rusting of

the said structures.

3.8 Mesco Feeder Take-Off.

The contractor shall supply, install, test and commission the line breakers, CTs and VTs,

disconnector switches with integral earth, post insulators and associated accessories for

each feeder.

The contractor shall recover the existing XPLE cables running from the power house to

the overhead line next to the substation. The recovered cables shall be handed over to the

employer

The contractor shall establish the take-off gantry structure, extend and terminate the

OHL conductors of the Mesco feeder to the 11kV busbar via the switchgear specified

above.

All substation structure shall be made of hot-dip galvanized steel to prevent rusting of

the said structures.

3.9 REMOTE OPERATION OF SWITCHYARD EQUIPMENT.

There shall be remote operation of the circuit breakers in the switchyard. The remote operation

shall be possible from the DCS and from control cubicles. The control circuits for the transformer

breakers shall be located in a suitable cubicle or in the transformer protection relay cubicles.

The control circuits for the line/feeder breakers may be located in the line protection relay

cubicle.

The On-load tap changers of the transformers shall also be operable as described above.

3.10 Inspections and Tests

Factory Inspections

Circuit breakers, disconnectors, current transformers, voltage transformers, surge arresters,

insulators, conductors, fittings and structures shall be tested in accordance with the

requirements of the relevant IEC standards.

Type certificates will be accepted in lieu of type tests; however where type test

certificates are unavailable the type tests shall be performed.

All equipment will be subject to routine tests in accordance with the relevant IEC

standard.

Tests on Completion

As a minimum, the following site tests shall be performed:

Circuit breakers:

(a) Visual inspection

(b) Insulation resistance

(c) Functional tests

(d) Interlocking test

Disconnectors:

(a) Visual inspection

(b) Insulation resistance

(c) Functional tests

(d) Interlocking test

Current Transformers:

(a) Visual inspection

(b) Insulation resistance

(c) Polarity

(d) Primary injection

(e) Ratio check at actual burden

(f) Measurement of burden

(g) Verification of excitation curve

Voltage Transformers:

(a) Visual inspection

(b) Insulation resistance

(c) Polarity check

(d) Turns ratio

Surge Arresters:

(a) Visual inspection

(b) Surge counter operation test

Transformers

Tests of insulation while in storage at site

The Contractor shall measure, at not more than weekly intervals, the insulation

resistance as specified, or as directed by the Engineer, using a d.c. voltage of 2 kV. The

Contractor shall investigate and take corrective action for any significant drop in resistance

compared to the values recorded at the factory or during storage.

Factory Acceptance Tests

Type tests may be waivered on submission by the Contractor of a certified type test report for

tests carried out by an independent accredited testing agency on transformers of the

same type, voltage and power rating. The certificates shall be provided to the Engineer no

later than 6 weeks before the scheduled factory testing date of the transformer. The decision

to waiver the test shall lie solely with the Engineer.

The transformer and ancillaries shall be subjected to the following tests at the

manufacturer’s factory.

Transformer Material Tests

The following material tests shall be carried out on all important stressed steel

components.

(1) Dimensional checks of all components and assemblies.

(2) Non-destructive Testing of Welds:

(3) Sample tests of core lamination material for magnetic characteristics and losses.

Transformer Hydrostatic Tests

The transformer complete with coolers and fittings and filled with oil shall be tested with an

incremental pressure of 35 kPa for 24 hours and shall be completely free of leakage.

Transformer Bushing Tests

Type tests, sample tests and routine tests in accordance with IEC 60137.

Current Transformer Tests

Type and routine tests in accordance with IEC 60044. For all 11kV current transformers the

dielectric test shall be applied to a test conductor fitted in the current transformers to represent

the busbar.

Tap-Changer Tests

Type and routine tests in accordance with IEC 60214.

Transformer Cooling Equipment, Protection and Alarm Devices Tests

The proper functioning of all thermometers, fan and pump controls and other devices shall be

tested.

Transformer Core Tests

A 2,500 V insulation tester shall be applied between each core bolt and the core

laminations after final tightening of bolts.

Complete Transformer Tests

The transformer shall be subjected to the complete series of type and routine tests in

accordance with IEC 60076, including:

(a) Temperature rise test (first transformer only)

(b) Dielectric type tests

(c) Measurement of winding resistance

(d) Measurement of voltage ratio and phase displacement

(e) Measurement of short circuit impedance and load loss

(f) Measurement of no-load loss and current

(g) Dielectric routine tests

(h) Tests of off-load tap-changer

(i) Partial discharge tests applied as a routine test for the Generator Transformer

(j) Full wave impulse-voltage withstand tests applied as a routine test to the Generator

Transformer.

During the tests of the complete transformer, core loss, excitation voltage and excitation

current shall be measured at 15 minute intervals over a period of 6 hours with the transformer

excited at rated frequency and 110 percent voltage. This test shall be made after the high-

voltage withstand tests.

Transformer Special Tests

Special tests in accordance with IEC 60076 shall be carried out including loss tests and

measurement of sound power level.

Generator Transformer loss tests shall be carried out to demonstrate compliance with

Performance Guarantees.

Tests on Completion

Transformer Preliminary Tests at Site

The preliminary tests including tests on transformer auxiliary equipment shall include the

following:

(a) Check impact recorders (where applicable) on installation, and if significant impact is

recorded carry out a comprehensive check for external and internal damage.

(b) Tests of transformer oil for moisture and dry out if necessary.

(c) High-voltage tests at the site test voltages specified in the relevant IEC Standards.

Where site test voltages are not specified in the standards the test levels shall be 75

percent of the factory test values.

(d) Measurement of winding resistance of transformer.

(e) Insulation resistance measurements at the specified voltages appropriate to the circuits and

equipment.

(f) Ratio and polarity check of current transformers and test of magnetizing curve.

(g) Proof of phasing or polarity of power cables.

(h) Proof of control connection and continuity of wiring for all control, protection, auxiliary

and alarm equipment in accordance with the overall diagrams as provided by the

Contractor.

(i) Operation of all control equipment at 80 percent, 100 percent and 110 percent of rated

voltage.

(j) Demonstration of sensitivity of gas and oil surge relays.

(k) Tests of all temperature and level indications, displayed quantities and analogue

outputs to show such items are within the accuracy limits specified.

Transformer Commissioning Tests

The Tests on Completion shall include the following:

(a) Demonstration of performance in service of all auxiliary equipment including tap changer.

(b) Demonstration that all controls, alarms and indications, including displays, operate

correctly.

(c) During the above tests the whole of the equipment shall perform without

adjustment.

(d) Tests to verify that the performance of transformers is in accordance with the Contract,

including monitoring of winding and oil temperature during sustained loading.

(e) The Reliability Test Period.

Applicable Grid Code

The applicable Grid code is available at the following website - www.erc.go.ke/

ANNEX 7: METERING SYSTEM

Technical Specifications

The contractor shall establish new metering systems for the station as described below. The

metering systems shall include:

Energy meters

Metering instrument transformers

Metering accessories

1. Energy meters

The energy meters shall conform fully to the requirements of IEC 60687, IEC 1358 and IEC

60211, for accuracy class 0.2 energy meters and other pertinent specifications.

The meters shall have an auxiliary supply of either 110VDC or 24VDC. This shall ensure the

meters are supplied even in situation of loss of the grid voltage.

1.1. Registers

Meter readings from fiscal energy meters associated with each generator shall be

interfaced via IEC 62056-21 protocol (Electricity metering - Data exchange for meter

reading, tariff and load control - Part 21: Direct local data exchange) and forwarding

the data to the KenGen CDC.

The following registers shall be read and displayed on the SCADA system: Revenue Data

(Active Energy Export, Active Energy Import, Reactive Energy Export, and Reactive

Energy Import), Demand Values (kW, kVA, kVAr and Maximum Demand), Voltage,

Current, Frequency, Power Factor, Load Profile and End of Billing Period Energy Register

Value (Monthly).

The energy register quantities to be displayed on the meter display shall be user-

programmable. The LCD display shall be capable of displaying 14 digits inclusive of digits

after the decimal point.

The meters shall have LED indicators for testing and indication of active energy and

reactive energy metering with one LED dedicated to active and the other to reactive

energy operation. The LEDs shall flash at a rate proportional to active power and reactive

power consumptions respectively.

1.2. Configuration

The energy meters shall be configurable for use in both 3-phase 4 wire and 3-phase 3-

wire 2 elements networks

The secondary voltage (line voltage) of the voltage transformers shall be user-

configurable between 100—500V. The energy meters shall be capable of operation with

voltages within this minimum ranges.

The energy meter shall be dual-rated for operation with both 1 Amp and 5 Amps and the

choice between the two shall be user-programmable.

Seals

The meters supplied shall have provisions for applying tamper-proof seals. Such seals

may be applied on the face/front covers, on the terminal block covers etc. Application of

seals on the provisions shall ensure that the connections on the meters shall only be made

when the applied seals are broken.

1.3. Memory

The meter shall have a non-volatile memory capable of data storage and with long-term

data retention.

The meters shall be capable of freezing billing readings on any user-selectable date of the

month and make these quantities be displayed on the SCADA system. At least twelve

billing historical data shall be stored in the memory and be retrievable by software action.

1.4. Clock

The meters shall be equipped with a real time clock controlled by a quartz crystal

oscillator. It shall be possible to reset the clock without loss of billing data. The energy

meter shall have an input signal that allows GPS time synchronization.

1.5. Programming software and hardware

The contractor shall provide programming software which shall be windows-based,

ready for use with the latest Windows operating software. The licence for the

programming software shall also be provided. The licences shall be for all the meters and

should enable the programmer to carry out all meter configurations. A similar copy of

the metering software and license shall be provided to Kenya Power for their use.

Two (2) Optical probes complete with a laptop and required accessories for

programming and downloading the meter data shall be provided. The optical probes shall

be provided with an USB at one end to facilitate connection to the programming device

and a magnetic optic head at the other end for hands-free attachment to the meter.

Protection against Penetration of Dust and Water Shall conform to the degree of

protection of IP51 as per IEC 529.

Training shall be carried out by the contractor on KenGen (3 staff) and Kenya Power (2

staff) on meter configuration for a duration of three days. It shall include a class room

set-up and on-site demonstrations.

2. Energy Billing System

There shall be a main metering for use by KenGen for billing purposes and check metering for

use by Kenya Power for back up purposes. The power generated from the station shall be metered

at the switchyard after the generator transformers by use of instrument transformers and energy

billing meters. The metering system installed shall have independent metering circuits for each

meter. Each metering circuit shall have a current transformer core and voltage transformer core

dedicated for the main meter and similarly for the check meter. No other devices shall be

connected to this circuits, whatsoever the situation.

Additionally, one voltmeter (one phase) and ammeter (one phase), one multifunction power

analyser per generator transformer, shall be installed in the switchyard control panel.

3. Metering of Generator Output

The output of the generator shall be metered at the generator phase terminals. The CTs shall be

class 0.5, inductive type with a suitable ratio. The secondary current of the CT shall be 1A. The

VT shall be inductive type with class 0.5 accuracy, voltage ratio 11000/√3/110/√3V, 50Hz.

There shall be energy billing meters for each generator located in the metering panels as

specified above. These meters shall be of accuracy class 0.5 with the other features as specified

above for export/import (clause 2).

Additionally, there shall be

a. Multi Function Power Analysers for each generator located in the unit control panel.

b. Analog indication meters for Current, Voltage, Active Power and Reactive Power for each

generator and located in the unit control panel.

c. Analog indication meters for Current (one phase), Voltage (one phase), Active Power and

Reactive Power for each generator and located in the auxiliary control panel. These

devices shall be connected directly from the CTs and VTs in the 12kV switchboard.

4. Metering of Auxiliary Consumption

There shall be metering of the following auxiliary supplies

New Station transformer

Old station transformer

Diesel Generator

The tariff meters used shall be of the same features as described above. However, they shall be

class 0.5. The auxiliary consumption shall be metered at 415VAC. The CT may be housed in the

main 415VAC switchboard. Alternatively, they may be placed in any other approved position.

The meters shall be mounted in the metering panel described above.

5. Metering of Transmission Lines

There shall be metering circuits for each of the three transmission lines. These circuits shall

include:

a. Line CTs and VTs.

b. Ammeters (one phase) and Voltmeters (one phase).

c. Multifunction power analysers.

Items (b) and (c) above shall be located in the Feeder control panel. The specifications for the

items in (a), (b) and (c) are provided in the clauses below.

6. Metering Panels.

There shall be metering panels for the installation of the billing meters. The panels shall have a

lockable door (key operated lock), a door switch operated fluorescent lighting and with a

minimum sheet thickness of 1.5mm.. They shall be vermin proof, free standing, have bottom

cable entry and glass panel suitable for viewing of the meter display readings. The panels shall

be located in the control room of the power house.

In this panel, every meter circuit shall be installed with test terminal blocks to enable testing of

meters by secondary injection without unscrewing of cables used in metering circuits.

The control cable used shall be of stranded copper conductor, PVC insulated, sheathed with steel

armour, overall PVC sheath and with a minimum cross-sectional area of 2.5sqmm for CT and

VT circuits. Such cables shall confirm to BS 6346.

The cubicles shall be two in number, one for KenGen (colour Orange) and one for Kenya Power

(colour Blue). Permanent labels of an acceptable size shall be affixed on the respective panels.

The labels shall read “KenGen Main Metering” and “Kenya Power Check Metering” respectively.

KenGen Main Metering panel shall have the following tariff meters installed:

a. Main Energy Billing Meters for Generators Transformers 1 and 2

b. Tariff meters for each generator

c. Tariff meter for each station auxiliary consumption

d. Tariff meter for the diesel generator.

Kenya Power Check Metering panel shall have the following tariff meters installed:

a. Energy Billing Check Meters for generator transformers 1 & 2

b. Provision for future installation of two tariff meters for Tana 1 & 2 lines. Such a provision

shall be of adequate capacity.

7. 11kV metering voltage transformer

The voltage transformers (VT) shall be of the outdoor, inductive type and shall comply with IEC

60044-2 and IEC 60186. They shall be of class 0.2 and a voltage ratio of 11000/√3/110/√3V.

The highest voltage for the VTs shall be 12kV as per IEC 60038. The contractor shall determine

the required burden rating of the VTs. On the secondary circuit, there shall be a miniature circuit

breaker for control of the VT output.

The VT shall have a minimum of two cores for metering purposes: One core for KenGen’s main

metering and one core for Kenya Power’s check metering. The primary circuit of the VT shall be

solidly earthed. The VT shall be mounted on galvanised steel structures of a height that ensures

and observes safety clearances. The structures shall be connected to the earthing system of the

switchyard.

The VT may have additional cores for use as the necessary.

8. 11kV metering current transformer

The current transformers (CT) shall comply with the requirements of IEC60044-1. The CTs

shall be of Class 0.2 with a secondary output of 1A, a highest voltage rating of 12kV as per IEC

60038. The contractor shall determine the required ratio and burden rating of the CTs.

The CT shall have a minimum of three cores: first core for main metering, second core for Kenya

Power’s check metering and third core for over-current protection of the line.

The CT shall be outdoor type and shall be mounted on galvanised steel structures of a height that

ensures and observes safety clearances. The structures shall be connected to the earthing system

of the switchyard.

9. Multifunctional Power Analysers

These are digital analysers used to measure, monitor and record power and energy quantities.

These specifications shall be applicable for all analysers supplied under this project.

The analysers shall be capable of indication instantaneous and average power values (kW, kVAr,

kVA, A, V, f, pf etc), instantaneous, cumulative and average energy values, as well as demand

values. The analyser shall be capable of recording both energy import and export and with a

non-volatile memory.

The analyzer shall have an LCD display with minimum four rows for indication. It shall be

possible to configure the analyser by use of function keys provided on the device, albeit via a

password. The analyser shall be 96 X 96mm in size.

The analysers shall be capable of 3-phase 3-wire and 3-phase 4-wire configurations, which

shall be selectable during configuration of the analysers.

The analyser should have a minimum of three 4 -20 mA outputs for Current, Voltage and Active

Power outputs. Such outputs may be connected to the Unit Control Board for indication

10. Power instruments

The power instruments include meters for indication ov voltage, current, power, reactive power

among others. They shall be of 96 X 96mm in size, 900 deflection, with a scale with black

numbering on a white background. The nominal values of the quantities measured shall be

indicated by a red mark. These specifications shall be applicable where such instruments are

specified.

ANNEX 8 - 415V SWITCH BOARD AND AUXILIARIES CONTROL

AUXILIARY SUPPLY TO THE POWER STATION

The station will be supplied by power via

1. Old alternative supply transformer, connected to the overhead 11kV busbar at the yard.

2. New Station transformer, connected on Section 2 of the indoor 11kV switchboard.

3. Emergency Diesel generator.

A single line diagram for the auxiliary supply has been shown as diagram 2.

There shall be an auxiliary supply switchboard rated at 415VAC. The switchboard supplied shall

be in conformance to international standards among them IEC 60158, IEC 60439-1, -2, -3 and

60947(applicable parts). The entire switchboard shall be manufactured in accordance with

known type-test assemblies whose type test results shall be submitted as part of bid documents.

The design and operational philosophy of the switchboards must be submitted for review and

approval by the employer before any assembly or manufacture can begin.

The proposed main switchboard is shown in drawing 3 “Proposed Main Auxiliary Power

Switchboard”. There shall be the following auxiliary switchboards:

1. Main Auxiliary Power Switchboard

2. Motor Control Centre (MCC) 1

3. Motor Control Centre (MCC) 2

4. Station Motor Control Centre (MCC)

1. MAIN AUXILIARY POWER SWITCHBOARD

The proposed switchboard is shown as drawing 3 ”Proposed Main Auxiliary Power

Switchboard” and shall have the following features:

The switchboard supplied shall be in conformance to international standards among

them IEC 60158, IEC 60439-1, -2, -3 and 60947(applicable parts). The entire

switchboard shall be manufactured in accordance with known type-type assemblies

whose type test results shall be submitted as part of bid documents.

Two bus-sections (1 & 2) with the new station transformer (Stx 1) on Section 1 and old

alternative feeder transformer (Stx 2) on section 2. There shall be a bus coupler to couple

the two sections. The bus coupler shall always be in OPEN position when in normal

operating conditions.

The operation philosophy of the three incomers to this switchboard is as follows:

o Station transformer 1 shall have the duty selection where all the loads shall be

supplied from this transformer as long as the switchboard is supplied with power

either from the grid or from generated units.

o In case of loss of supply from the station transformer 1, automatic change over to

the alternative feeder shall occur. Automatic change over from the alternative

feeder to the station transformers shall occur as soon as the supply on the station

transformer has stabilized.

o In case of loss of both the station transformer one and alternative feeder, the

emergency diesel generator shall start and its circuit breaker closed automatically

to supply the power house loads.

o Automatic change over from the emergency diesel generator to the station

transformer or alternative feeder shall occur as soon as the supply on the station

transformer has stabilized.

The incoming breakers shall be Air Circuit Breakers of appropriate rating. The breakers

shall have over-current settings for appropriate protection of the incoming feeders. The

feeders shall incorporate robust under-voltage relays in their control circuits.

There shall be voltage and current indications for each incomer by use of multifunction

power analysers and analog meters. The features of the power analysers are as specified

in annex 7, clause 8. The ammeter (one phase) and voltmeter (one phase) shall

connected via CTs, VTs or by direct connection. These devices shall be installed in this

switchboard.

Outgoing circuits shall be fitted with air circuit breakers or MCCBs as may be

appropriate. The contractor shall rate the circuits as in good engineering designs. The

outgoing circuits are shown on the single line diagram for this switchboard. The

contractor may add outgoing circuits to this board as per his design.

The control voltage shall be either 110VDC from the station batteries or 24VDC

converted from the station batteries supplies.

There shall be local indications using LED lamps for ON/OFF/TRIP status for the

incoming and outgoing feeders/circuits. The ON/OFF/TRIP status shall also be indicated

in the SCADA screens via the PLC. Additionally, there shall be indications for ISOLATED,

SERVICE, TEST positions with the necessary safety interlocks.

There shall be local/remote/auto selector switches. Remote selection shall allow control

of the circuit from a remote location (SCADA/PLC) while auto selection shall be used for

automatic changeover control (hard-wired) via under-voltage relays of the switchboard.

Power supply to the Drainage Pumps , AC emergency lighting and the Winch shall be

connected to Section 2 of the busbar to ensure that they can be supplied by the emergency

diesel generator incase of total loss of the grid.

The drainage pumps shall be supplied via DOL starters. The winch shall be supplied from

this switchboard according to the specifications of the contractor

rehabilitating/renewing it.

The incomers to the switchboard shall be metered as detailed under the specification for

metering systems.

In addition, there shall be multifunction power analysers and analog panel meters for

voltage and current indication.

2. MCC 1, MCC 2 and STATION MCC

The MCC 1 & 2 shall supply power to the generator equipment and auxiliaries while the station

MCC shall supply power to the non-generator related loads. MCC 1 shall be dedicated for

Mathioya River units and MCC 2 shall be for Maragua River units. The proposed MCCs are

show as drawings 4 “Proposed Unit MCC) and Drawing 5 “Proposed Station MCC”.

The specifications for the MCCs are as follows:

The switchboard supplied shall be in conformance to international standards among

them IEC 60158, IEC 60439-1, -2, -3 and 60947(applicable parts). The entire

switchboard shall be manufactured in accordance with known type-type assemblies

whose type test results shall be submitted as part of bid documents. The TTA shall be form

3b with withdrawable drives and breakers.

There shall be two incomers into each MCCs – one incomer from each bus section –

connecting to a common busbar.

The incomer breakers shall be Air Circuit Breakers of appropriate rating. The breakers

shall have over-current settings for protection of the incoming feeders. The feeders shall

incorporate robust under-voltage relays in their control circuits.

Outgoing circuits shall be fitted with direct-on-line (DOL) starters for pump supplies

and appropriate circuit breakers for other circuits. Each Pump starter shall incorporate

phase failure relay in the circuit for the protection of the supplied motors. The controls

per circuit shall be totally withdrawable from their cell locations.

The control voltage shall be either 110VDC from the station batteries or 24VDC

converted from the station batteries supplies.

There shall be local indications using LED lamps for ON/OFF/TRIP status for the

incoming and outgoing feeders/circuits. The ON/OFF/TRIP status shall also be indicated

in the SCADA screens via the Unit PLCs for MCC1 & 2 and via Common PLC for Station

MCC. Additionally, there shall be local indications for ISOLATED, IN SERVICE positions

with the necessary safety interlocks.

There shall be local/remote/auto selector switches. Remote selection shall allow control

of the circuit from a remote location (SCADA/PLC) while auto selection may be used for

pump control by switches or applicable instruments.

The number of outgoing circuits shall be determined by the contractor’s proposed

circuits/loads. Two spare cells shall be supplied complete with a DOL starter of a similar

rating to the highest load in each MCC. Additionally, there shall be two empty spares

cells for future use by the employer. The empty cells shall be supplied ready for fitting

with starters/controllers by the employer.

There shall be local indication of current and voltage on each incoming and outgoing

circuit by use of analogue gauges of appropriate size.

Factory Acceptance Tests

Routine and type tests shall be carried out on the switchboards, circuit breakers,

contactors, current and voltage transformers, and protection relays in accordance

with the applicable IEC standards:

Switchboards - Routine tests IEC 60947

Circuit breakers - Type tests on one of each type IEC 60056

- Routine tests IEC 60439

Contactors and control gear - Routine tests IEC 60947

Current transformers - Routine, type and impulse tests IEC 60185

Potential transformers - Routine, type and impulse tests IEC 60186

Protection relays - Routine tests IEC 60255

Factory acceptance tests shall be witnessed by the Client.

Tests on Completion

The 415 V switchboards and switchgear shall be subject to inspection testing and

commissioning. The Contractor shall provide all test sets and test apparatus required for

carrying out the tests. The following site tests shall be performed:

(a) Visual inspection

(b) Insulation resistance tests

(c) Continuity tests

(d) Routine high voltage tests

(e) Protection relay primary and secondary injection tests

(f) Function tests to verify tripping, closing, interlocking, alarms and indications, etc.

DC equipment

Factory Acceptance Tests

The battery chargers, d.c. distribution boards and their components shall be tested in

accordance with the applicable IEC Standards or equivalent.

The works tests shall include, but not be limited to:

(a) Temperature rise;

(b) Insulation resistance;

(c) Operational tests;

(d) Radio interference tests;

(e) Ripple measurement of the charger output without battery connected.

Tests on completion

The following tests on completion shall be carried out as a minimum:

(a) Visual inspection;

(b) Insulation resistance;

(c) Functional tests;

(d) Setting and functional tests of protective devices;

(e) Tests to confirm the charger’s rating;

(f) Ripple measurement of the charger output with battery connected.