IS 15953 (2011): Supervisory Control and Data Acquisition

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IS 15953 (2011): Supervisory Control and Data Acquisition(SCADA) System for Power System Applications [LITD 10:Power System Control and Associated Communications]

© BIS 2011

B U R E A U O F I N D I A N S T A N D A R D SMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

October 2011 Price Group 11

IS 15953 : 2011

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Indian Standard

SUPERVISORY CONTROL AND DATA ACQUISITION(SCADA) SYSTEM FOR POWER SYSTEM

APPLICATIONS

ICS 33.040.60;33.200

Power System Control and Associated Communications Sectional Committee, LITD 10

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the PowerSystem Control and Associated Communications Sectional Committee had been approved by the Electronics andInformation Technology Division Council.

The Committee responsible for the formulation of this standard has reviewed the provisions of the followingInternational publications and has decided that these may be used in conjunction with this standard till IndianStandards on these subjects are published:

IEC 60068 series Environmental testing

IEC 60870-2-1 : 1995 Telecontrol equipment and systems — Part 2: Operating conditions — Section 1:Power supply and electromagnetic compatibility

IEC 60870-5-101 : 2003 Telecontrol equipment and systems — Part 5-101: Transmission protocols —Companion standard for basic telecontrol tasks

IEC 60870-5-104 : 2006 Telecontrol equipment and systems — Part 5-104: Transmission protocols —Network access for IEC 60870-5-101 using standard transport profiles

IEC 61131-3 : 2003 Programmable controllers — Part 3: Programming languages

IEC 61850 Communication networks and systems in substations

IEEE Green book standard 142 : 1991 IEEE Recommended practices for grounding of industrial andcommercial power systems

The composition of the Committee responsible for the formulation of this standard is given in Annex D.

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960‘Rules for rounding off numerical values (revised)’. The number of significant places retained in the rounded offvalue should be the same as that of the specified value in this standard.

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IS 15953 : 2011

Indian Standard

SUPERVISORY CONTROL AND DATA ACQUISITION(SCADA) SYSTEM FOR POWER SYSTEM

APPLICATIONS

1 SCOPE

The SCADA system specifies facilities for monitoringand control functions of distributed process from acentral location. The SCADA system described hereare meant for operation of the transmission anddistribution power system network. This standardprovides definition and guidelines for the specification,performance analysis and application of supervisorycontrol and data acquisition (SCADA) systems for usein electrical utilities. These can also be used for remoteoperation of a sub-station.

The SCADA systems typically use computer systemsconsisting of servers, workstations and front endprocessors at a central location, referred as the controlcentre and a data acquisition and supervisory controldevice or a group of devices, generally referred asremote communication and control interface (RCCI),located in the sub-stations/power stations. In thisstandard the term RCCI denotes any data acquisitionand supervisory control device, for example intelligentelectronic devices, programmable logic controller, baycontrol modules, remote terminal unit, etc, that directlycommunicate to a remote control centre. The presentday sub-stations are adopting new technologies likesub-station automation systems which perform the dataacquisition and supervisory control functions similarto a RCCI but in more detail. The sub-stationautomation systems generally have gateways forcommunicating with the computer systems at thecontrol centres. This standard does not cover therequirements of sub-station automation systems.

SCADA system is deployed as an integrated componentof energy management systems/distributionmanagement systems in present day control centres.This standard does not cover the details/functioningof the advanced applications (like EMS/DMS) and onlya reference is given.

2 REFERENCES

The standards listed in Annex A are necessary adjunctsto this standard.

3 TERMINOLOGY

For the purpose of this standard the definitions given

in IS 12746 (Part 1/Sec 3), IS 1885 (Part 50) andIS 1885 (Part 52/All sections) shall apply.

4 FUNCTIONAL CHARACTERISTICS

A SCADA system comprises of a controlling systemreferred to as control centre and a controlled systemreferred to as RCCI. A SCADA system ranges in sizeand complexity from a single control centre with a non-redundant work station to a hierarchical control centresetup with redundant multiple servers. The controlcentres are sometimes duplicated with a backup controlcentre for critical systems. The controlled system maycomprise of a single RCCI or hundreds of RCCIsdistributed over a wide geographical area, just like thepower system network, communicating over a diverseset of communication mediums. Also, the SCADAsystem governed by this standard may perform someor all of the functions identified in this standard.

The term Control Centre and Master station have beenused interchangeably in this standard depending uponthe context. However, in a modern day control centre,the term Master station refers to an entity whichgenerally does the communication with the fielddevices (like RCCIs) using a communication protocol.Similarly the term RCCI has been used to refer to allintelligent devices which are installed in the filed sitesfor the purpose of data acquisition from the process.

Figure 1 Illustrates the possible types of data andcontrol flow between a master station and a RCCI.

4.1 Typical Equipment Functional Diagrams

The typical equipments in a control centre and a RCCIare illustrated using functional diagrams.

4.1.1 Control Centre Functional Components

The functional components of a control centre areillustrated in Fig. 2. A redundant system with dualserver in hot standby configuration is illustrated inFig. 2; however, a single server configuration may beadequate for some non-critical applications.

A user needs to specify the requirement of redundancyin the functional components depending uponcomplexity and criticality of his application. In somecases it may be required to have a backup control

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IS 15953 : 2011

Computer servers and work stations See Fig. 2 for details

Communication Interface

Supervisory Control: a) Trip/Close

b) Raise/Lower c) Open/Close d) Stop/Start e) Set point values

Parameter Download: a) Control Programs1)

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IS 15953 : 2011

centre, at a distant geographic location to cater toemergency situations leading to loss of primary controlcentre due to natural calamities, fire, flood, etc.

A backup control centre (BUCC) adds to reliabilityand may be considered whenever there is credible threatto control centre from accident, natural disaster, orattack (physical or cyber) or wherever underlyingsystem are unmanned or are critically required to beoperational continuously (24 × 7 × 52). The minimumrequirement for a backup control centre shall includedata acquisition from underlying RCCIs/controlcentre(s) as well as peer control centres. Thecommunication lines/equipment shall not be dependentupon existence of the main control centre. The backupcontrol centre shall have a communication link ofadequate capacity to main control centre for carryingdata as per the specified requirement. This normallyincludes data exchange like telemetred data, operatorentered data, schedules data, historical data, reports,source code, database model data, display files, systemmonitoring and health check data, etc, between mainand backup control centre whose volume depends uponthe design of the SCADA system and the operatingphilosophy of the utility. The operation philosophy forbackup control centre may be of hot standby, coldstandby or independent modes of operations.Regardless of the level of sophistication of the BUCC,the most important considerations when implementinga BUCC is the availability of both voice and datacommunication facilities and the time to make itoperational in case of failure of main control centre.The user shall specify the requirement of remotelymonitoring and maintaining the backup control centre,if desired.

The control centre may have different applicationservers like SCADA servers, EMS servers, front endprocessor, ICCP servers, historical data server, web

server and peripheral devices like local area networkswitches, routers, printers, time reference such as a GPS(global positioning satellite) based time synchroni-zation equipment, external storage devices, etc. TheGPS is used as a standard time reference for keepingthe time of the control centre computer systems andthe RCCIs synchronized.

The control centre may act as a source of real-timeand historical information about the power system anda utility may require this data to be made available toother users within the organization and to outsideagencies like energy traders, customers, regulatorycommissions, government agencies, etc. It is preferableto have a separate WEB enabled system to address theseneeds so that the realtime information about the powersystem can be viewed using simple web browsers onintranet or internet. The WEB enabled system shall alsohave adequate information security measures likefirewalls, intrusion detection system/intrusionprevention system, encrypted communication, etc, inaddition to normal security measures like userauthentication and authorization.

A utility may also need the ability to operate the powersystem from sites other than the control centre. Use ofremote operator workstation is preferable in this case.Sometimes a hierarchical set-up of control centres maybe required, to match the organizational needs of autility/power system. The organization of controlcentres in multiple hierarchical levels like area loaddispatch centres, state load dispatch centres, regionalload dispatch centres and a National Load Dispatchcentre is one such example. The control centres in ahierarchical set-up typically exchange real-time dataand other information among them. Use of the intercontrol centre communication protocol (ICCP) can bespecified in all such cases to ensure interoperability. Ahierarchical set-up of control centres is shown Fig. 3.

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IS 15953 : 2011

4.1.2 RCCI Functional Components

The functional components of an RCCI are given inFig. 4. Various interconnections of master station(s)and RCCI(s) are illustrated in Annex B.

4.2 SCADA System Functional Characteristics

This clause provides guidance for both users andsuppliers to jointly define the functional capabilitiesthat may be required in a SCADA system.

Each generic function is described in terms of theminimum features or characteristics that shall beaddressed to adequately define the function.

When the feature or characteristic is fixed by the designof the equipment, the burden of definition rests on thesupplier (for example number of inputs/outputs percard). However, variable features (for example, rangeof inputs, scaling resistors, switch settings, andsoftware) shall be defined by the user.

4.2.1 Communication Capabilities with RCCI

The communication links between a master station(s)and RCCI(s) and between a sub-master RCCI and itsslave RCCIs, can be on any suitable communicationmedia like a twisted pair copper cable, PLCC, radio,fibre optic, VSAT, leased line, dial-up, GSM or CDMA,etc. The choice of communication media depends upon

the application for which the SCADA system is used,the quantum and frequency of data to be exchanged,geographical spread of the control system andeconomy. In power utilities dedicated communicationlinks are preferred as the availability of communicationlink determines the reliability of the SCADA system.However, if only acquisition of data is envisaged atlong intervals (like an hour) and no real time controloperation is to be performed in that case a dial-up linecan also be used.

The communication protocols typically used requiresa master station to initiate a message transaction. Insome cases the RCCI can initiate a communicationmessage. The requirements of the communicationprotocol for communicating between the masterstation(s) and the RCCI(s) shall be defined and astandard communication protocol shall be utilised.

A control centre (master station) shall implement allthe features of the standard communication protocolsuch that minimum integration effort is required forintegrating a RCCI in future. The communicationprotocol attributes to be specified may include,

a) Protocols to be supported;b) Protocol messages to be supported;c) Protocol applications services to be

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IS 15953 : 2011

d) Report-by-exception polling;e) Channel monitoring (main and backup);f) Communication error reporting, failure

criteria, and recovery;

g) Automatic channel switching between mainand backup channels;

h) Channel diagnostic/test provisions;j) Type of communication equipment interfaces;

k) Type of communication channels/media;m) Number of masters to which a RCCI is

required to report; andn) Number of RCCIs per channel and/or

channels per RCCI.

4.2.2 Data Acquisition

Data acquisition is the process of collection of data bythe RCCI from the field and by the master station fromthe RCCI. The type of data to be acquired, itsperiodicity, the update requirements and ultimate pointcounts need to be specified by the user. Systems withreport-by-exception functions shall have the capabilityto report all data for initialization and periodic integritychecks.

As a general rule, not all the data available in asub-station may be required by the RCCI/SCADAsystem. The data required by SCADA system shall begoverned by a data acquisition principle of the user,which shall identify the minimum data which isrequired for monitoring of the substation for the desiredapplications at the control centre.

The process data in an electrical utility can be mainlycategorized into the following types:

a) Analog inputs — Continuously varyingparameters like voltage, current, power, powerfactor, transformer tap position indication,temperature.

b) Digital inputs — Switchgear (Isolator/breaker/earth switch) status, alarm status, SOEinputs, relay indications.

c) Pulse accumulator value — Energy values,rainfall.

d) Digital outputs — Control of switchgear,raise/lower control of tap position oftransformers, reset of relays.

e) Analog outputs — Set point controls forgenerators, HVDC controller.

The characteristics for each type of data shall be definedindividually. These shall include ranges of data input,scale factors, acquisition rates, and data updaterequirements as applicable.

4.2.2.1 RCCI data acquisition

The capacity (total number of input points) and rate ofacquisition (inputs per second/millisecond) for fielddata interfaced to the RCCI equipment shall be definedfor all applicable data types.

The analog inputs to the RCCI are generally throughtransducers (see IS 14570) and in some cases directlythrough CT/PT connections. The inputs from atransducer can be scanned every 1 sec and from CT/PTinputs can be sampled at least half the frequency ofthe a.c. supply that is 25 Hz. The following shall bespecified for analog input characteristics of the RCCI:

a) Ranges of analog input signal (in mA, mV,V, A);

b) Analogue to digital converter resolution of16 bits (see IS 14570);

c) Accuracy of measurement for transducers/RCCI card;

d) Input overload protection;e) Input impedance/output impedance;f) Temperature coefficient of accuracy; and

g) Residual current.

When multiple parameters of a feeder are required thena multi-function transducer can be used.

The status input to the RCCI is measured by discretestates of the signal such as the presence or absence ofa voltage, current, or a contact in the open or closedposition. The status inputs are generally scanned every1 millisecond by the RCCI. The following shall bespecified for input characteristics of the RCCI:

a) Wet or dry contact status inputs;b) Sensing voltage for contact wetting;c) Current limiting;

d) Isolation between sensing voltage and powersupply;

e) Optical isolation;f) Debounce filtering (in 4 to 25 millisecond

range);

g) Buffer for storage of status inputs for shortcommunication problems;

h) Double status input or single status input formonitoring;

j) Time stamping with accuracy of1 millisecond; and

k) Time stamping resolution of 1 millisecond.

The RCCI may also acquire data from slave RCCIs orIEDs using a communication protocol like MODBUS.The RCCI in such a case acts as a sub-master. If

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IS 15953 : 2011

required, these features shall also be specified. Themaster station functions allocated to such sub-masterRCCI shall be defined using the applicable precedingsub-clauses. This is the responsibility of both the userand supplier. The user shall define the applicablecharacteristics as follows:

a) Data acquisition methodology;b) Communication protocol;c) Number of points;

d) Scan interval;e) Downloading characteristics; andf) Data pass through/processed in the sub-master

RCCI.

The RCCI shall be capable of sending data to theSCADA system either periodically through a scangroup or through report by exception mechanism asper the desired communication protocol to the controlcentre. The RCCI shall be capable of sending dataspontaneously (balanced communication) whichreduces data traffic on the communication channelhowever when multiple RCCIs are connected to amaster station on the same communication channel theunbalanced mode is used.

4.2.2.2 Control centre (master station) data acquisition

The data acquisition capability for SCADA systemshall be defined in terms of the followingcharacteristics:

a) Type of data to be acquired;

b) Scan groups — A scan group is a set of datawhich is grouped together for the purpose ofacquisition from the master station. Numberof scan groups, size of each scan group andthe points in each scan group are to be defined;

c) Scan cycle — Number of scan cycles (A scancycle is the time to complete the acquisitionof a scan group from a RCCI). The scan cyclemay vary from 1 s to 1 h;

d) Capability to acquire data by periodic pollingand by exception polling shall be defined;

e) Capability for executing demand scan of theRCCI that is polling the RCCI on events suchas supervisory control, RCCI initializationand on user demand shall be specified;

f) The capacity (total number of input points)and rate of acquisition (inputs per second)from RCCI for each data type; and

g) Provision for future expansion and additionof other type of data.

The data acquisition process in the control centre shallalso be capable of acquiring data from non-RCCI

sources such as another control centre through acommunication protocol like ICCP. This protocol isused for data exchange between different controlcentres in a hierarchical setup or between controlcenters of two different utilities.

4.2.3 Other Communications between SCADA andRCCI

In addition to acquisition of data from the RCCI, theSCADA system shall also be capable of exchangingthe following information.

4.2.3.1 RCCI database download

Typical utility scenario involves changes in theelectrical network such as addition/deletion of devices,changes in the CT/PT ratios. The RCCI databaseconfiguration needs to be modified to match thesechanges. The RCCI shall support download of itsdatabase configuration files from the control centrepreferably in the framework of the communicationprotocol being used. This will facilitate the changingof settings and downloading a new database in theRCCI remotely from the control centre location withoutmaking a visit to the remote site. Necessary toolsrequired to generate the RCCI database configurationfiles are often installed on a standalone system.

4.2.3.2 RCCI test mode

The SCADA system shall support a ‘test mode’ whichallows the RCCI interface/database to be tested/calibrated remotely from the control centre. In thismode, the data acquired from the RCCI is not to beused by the SCADA system but is directed to a testdisplay. The test display shows the actual values beingreceived from the RCCI in the test mode. The real-time database of the SCADA system retains theprevious value from the points collected via the RCCIbefore it was placed in the test mode.

4.2.3.3 RCCI time synchronization

Each RCCI shall have a real-time clock which will beused by the RCCI for time stamping of sequence ofevents. The stability of this clock shall be specifiedbased on the accuracy requirement of the SOE and thetime synchronization method used. The RCCI clockshall be synchronized either from the master stationusing the communication protocol or from a timesource like GPS receiver.

The RCCI real-time clock shall be backed-up with asuitable secondary source of power like a lithiumbattery so that the real time clock continues to functioneven when RCCI is disconnected from its primarysource of power supply in cases where RCCI is notsynchronized from local/remote master station/GPS.

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IS 15953 : 2011

4.2.4 Data Processing

Data processing capabilities of the SCADA system andthe RCCI shall be defined for each applicable datatypes. A processing applicable to all the data types isthe data quality processing in the SCADA system. Thedata quality indicates to the user the attributes of thedata such as the accuracy and dependability on the data.The following data quality codes are generallyrequired:

a) Non-updated — Data is not being acquiredfrom the source and the value being displayedis old.

b) Manually replaced — Data is manuallyentered by the user.

c) Scan inhibit — Data has been inhibited frombeing updated from the source by the user.

d) Alarm inhibit — Alarming process for the datahas been inhibited so that alarms will not beindicated to the user.

e) Limit override — Limit on analog value hasbeen overridden with new limit values.

f) Unreasonable — The value reported by theRCCI is not within the defined range.

g) Questionable — The value is questionablebecause of factors like A/D drift or fault.

4.2.4.1 Analog data

The analog data processing capabilities to be supportedat both the SCADA system and the RCCI shall bedefined. Particular attention shall be given to input datavalidity processing (for example the validity of thedata) and to the interface between the supervisorycontrol function and the analog data processingfunction.

The following analog data processing is generally donein a SCADA system:

a) Reasonability processing check shall be madeto see that the data being received from theRCCI falls within a range of values(reasonability limits). The reasonability checktakes care of wrong CT/PT ratio in databaseand malfunction of transducers. Furtherprocessing of the data takes place only whenthe value is considered to be reasonable.

b) Data conversion to engineering units istypically required before analog data is usedby other software, printed or displayed asoutput. The mathematical equation(s) used toconvert analog values represented by rawcounts into the corresponding engineeringunits shall be user definable. Specific attentionshall be given to sensor and transducer scalefactors that may be provided by the user.

c) Data processing-by-exception may be afunction included as an alternative toprocessing every input on every scan as itreduces the requirement of computing powerwithout affecting the accuracy of themeasurements. A dead band (1 percent to5 percent) is to be specified which shall beused for determining change. This processingcan be done either in the RCCI or in the masterstation or in both.

d) Data filtering may be required to smooth databefore it is used by other functions. When thisfunction is included, the equation used shallbe defined and the time delay, introduced bythe filtering, specified.

e) Data limit checking is typically included todetermine, if the value of an analog point iswithin the safe and operational limits. Thenumber of high or low limits accommodatedand associated return-to-normal deadbandprocessing shall be defined. Specific attentionshall be given to the procedure for revision oflimits and deadband values by the user. Theuser may specify the requirement of differentAlarm limit sets for the different seasons likesummer limits and winter limits. The methodof invoking a alarm limit set shall also bespecified.

f) Sign conversion — Convert the sign of theanalog values as per convention.

The following analog data processing isgenerally done in RCCIs:

1) Detect an open input to an analogchannel;

2) Identify unreasonable values (out ofrange inputs);

3) Detect a drifted or faulty A/D converterRCCI card (Applicable only when theRCCI does not have auto correctionfeature for A/D converter); and

4) Validity of time stamp.Further the conversion of analogue data to engineeringunits [see (b)] may also be specified as part of RCCIcapability.

4.2.4.2 Status data

Status data is used to describe a physical quantity (forexample switchgear position) that has various possiblecombinations of discrete states. The status dataprocessing options to be supported at the SCADAsystem and the RCCI shall be defined by the user.

The status data processing generally done in RCCIincludes time stamping to required resolution,

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IS 15953 : 2011

capturing multiple changes of an input for onwardtransmission, value inversion, chatter filtering, changedetection (including comparing complimentary pointswith adequate delay to suppress reporting ofintermediate position), data report by exception.

The status data processing generally done in controlcentre includes,

a) conversion to engineering values;b) inversion;c) detection of abnormal state definition;d) multiple state change detection — open,

closed, transit; ande) change detection and alarm processing.

4.2.4.3 Accumulator data

The following characteristics shall be defined whenpulse accumulation and/or accumulator data processingis included:

a) Input circuit (two or three terminal and howinput circuit operates);

b) Sources of freeze command, if any (internal/external);

c) Reset command (if any);d) Ranges of values (RCCI and master station);e) Nominal and maximum counting rates;f) Source of memory power; andg) Input voltage if externally powered.

4.2.4.4 Sequence-of-events (SOE) data

Sequence of events (SOE) data are RCCI events withtime stamps. It shall be possible to define any or allthe digital inputs of the RCCI as SOE data.

The following characteristics shall be defined whenSOE data acquisition capability is included:

a) Time resolution of time stamping at RCCI;b) Time accuracy between any two RCCI;c) Number of SOE inputs per RCCI;d) Size of buffers (number of SOE events that

can be stored) per RCCI per master;e) Time (minimum/maximum) between

successive change(s) of an input; andf) Method of indicating that SOE data is

available at the RCCI.

4.2.4.5 Calculated data

Calculated data is derived after performingcomputations on data acquired from the RCCIs andother sources. Generally, the calculations are performedin the SCADA system but may be required at the RCCIalso. The following characteristics shall be definedwhen the capability of computing data (which are notdirectly measured) is included:

a) Location (RCCI or control centre or both);b) Mathematical/logical/statistical functions

required;c) Resulting data types (numeric or logical, or

both);

d) Data quality inheritance;e) Number of arguments in a calculation;f) Type of data to be used in calculation; and

g) Calculations required on realtime data and onhistorical data.

4.2.4.6 Alarm data

Alarms are conditions in the process or in the SCADAsystem that require user notification when detected.The following characteristics shall be defined whenthe capability to process and report alarm conditionsis included:

a) Conditions reported as alarms;

b) Methods of acknowledgment (single orselection or groups);

c) Methods of highlighting alarms (for exampleflash, audible tone, etc);

d) Information in alarm messages (time, event/device identification, Operation/action);

e) Priority of alarms (up to 8);f) Size of alarm queue(s);g) Queue management (for example time

ordered);

h) Destination of alarms — alarm summarydisplays, loggers, history database;

j) Alarm inhibit feature;k) Advanced alarm management functions for

intelligent processing of alarms; and

m) Alarm sorting/analysis/organization.

4.2.4.7 Topology processing

The SCADA system topology processing function,shall be capable of analyzing the open/close status ofswitching devices in order to identify the energized/de-energized condition of a power system equipment.This information about the state of the power systemdevices is visualized by a operator on a single linediagram or a network diagram. The visualization shallbe capable of colouring topology to indicate voltagelevel and/or identify the source of feed.

4.2.5 Supervisory Control Characteristics

Supervisory control enables controlling of devices fromremote. The devices to be controlled includeswitchgear, transformer tap position, capacitor bankswitching, AGC of generators etc. The characteristicsof such a control capability shall be defined definition

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IS 15953 : 2011

of characteristics common to all control interfaces shallinclude following:

a) Type of control command (Digital/analog,momentary, persistent, variable pulse);

b) Operator actions (Select once-operate once/Select once-operate many) and systemresponse;

c) Control sequence (Direct or select checkbefore operate);

d) Security of control sequences operation(Checks for tagging/RCCI telemetry failure/user defined software interlocks);

e) Control command feedback;

f) Group control (One command to controlmultiple devices);

g) Sequential switching plans; andh) Control possibility by other applications.

4.2.5.1 Equipment control with relay interface

Control using a relay output shall be defined as follows:

a) Dwell time of relay contacts;

b) Number of relays that can be simultaneouslyenergized in each type of RCCI processingactions (for example logging and alarmsuppression); and

c) Relay contact ratings (voltage/current/ac ordc).

4.2.5.2 Equipment control with set point interface

Control using a set point output shall be defined asfollows:

a) Resolution of set point value;b) Duration of output value;

c) Processing actions (for example limit check,equation, and alarms); and

d) Electrical interface.

4.2.5.3 Equipment/process control with IEDs

Control using an electronic interface shall be definedas follows:

a) Timing diagram of signals,b) Interface communication protocol,

c) Processing actions associated with control, andd) Physical interface.

4.2.5.4 Automatic control functions

Automatic control functions can be used for executingcontrols based on certain system conditions. Some ofthe applications where this can be utilised is load shedbased on frequency, transformer tap position changefor controlling voltage profile, taking in service of

capacitors based on reactive power compensationrequirements. When the capability to automaticallycontrol external devices is required, the characteristicsof such control capabilities shall be defined as follows:

a) Location of automatic control logic (RCCI orcontrol centre);

b) Control equation(s);c) Feedback value and accuracy, if closed loop;

d) Frequency of execution;e) User alterable control parameters;f) Associated logging or alarming;

g) Method of altering control logic; andh) Use of standardized programming language.

4.2.6 Use Interface Characteristics

User interface is the application through which a userinteracts with the SCADA system at the control centreand with the RCCI. The design and implementation ofuser interface shall be intuitive and user friendly. Theuser interface shall support full graphics user interfacefeatures and utilize a windows based environment. Theuser shall be able to perform all the activities byinvoking simple menus and shall not be required totype commands. Short cut keys shall be definable sothat advanced users can navigate quickly. User interfaceshall be uniform and have common look and feel forthe various applications in the SCADA system and forperforming different activities like operation,programming and development, etc.

The RCCIs generally does not require a elaborate userinterface. However most modern RCCIs are providedwith a simple text based user interface. Some RCCIshave inbuilt web server, which allows a user to interactwith the RCCI using a web-browser. The requirementof a web-based user interface for the RCCI shall bespecified by the user, if required. The RCCI can alsobe connected to a logger for printing of sequence ofevents/alarms. The RCCI can optionally have a GUIdisplay, for example LCD for displaying informationand allowing user interaction. RCCIs shall haveindication, for example LEDs to report the status ofthe input-output (I/O) cards and each of its channels.The indication for individual channels of an analoginput card is generally not provided by all the vendors.

The user interface functions characteristics shall bedefined according to the following sections.

4.2.6.1 Types of user

There are different activities like operation,management, maintenance, development, study etc, tobe performed by different users of SCADA system.The SCADA system shall have a provision for havingdifferent user modes to support the working

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environment required for the different activities. Thefollowing user modes may be specified:

a) Dispatcher/Operator — Users who use theSCADA system for operation of the powersystem.

b) Supervisor — Users responsible foroperations management of the SCADAsystem.

c) Engineer — Users responsible for operationssupport and maintenance activities who haveaccess to certain SCADA/EMS/DMS systemfunctions.

d) Programmer — Persons responsible forcontinuing development and maintenance ofthe SCADA/EMS/DMS systems.

4.2.6.2 Function and data access security

A mechanism for defining and controlling user accessto the SCADA system at each console shall beprovided. Password security shall at least be providedfor access to the system, its operating system, its layeredproducts and other applications.

Also access to the SCADA/EMS functions, displays,reports and database elements shall be restricted bypre-assigned operating jurisdictions. These operatingarea assignments are made when the function, display,report, or database element is being defined.

An operator console shall be assigned one or moreoperating jurisdictions and each time a user attempts aconsole action such as calling a display, entering adisplay data, executing a supervisory control action,managing an alarm, etc, the console’s assignedoperating jurisdiction is to be compared against theoperating jurisdictions assigned to the function, display,report, or database element.

In a control centre with multiple servers, the userauthentication and authorization shall be performedsuch that a user of the SCADA system is required toenter his credentials only once. The user shall then beallowed to have access to the SCADA system resourceon any of the server seamlessly.

User authentication and authorization shall be specifiedfor the management of all the peripheral devices also.

The RCCI local user interface shall also have a userauthentication and authorization check for executinga supervisory control, reading the status of RCCIinputs, modification of database, etc.

4.2.6.3 Graphical user interface features

The following features of the GUI required shall bespecified by the user:

a) Number of display windows;b) Number of saved layout of displays/windows

for each user login wise;c) Number of layers;

d) Number of declutter levels;e) Support for overlays, pan, zoom;f) Number of steps in pan/zoom;

g) Data presentation in different type of displays;and

h) Display requests mechanism-selection frommenu, cursor target selection, alarm/eventselection, entry of display name or number ina display selection field, forward and reversepaging through series of display, zoomingfrom an overview display to an area of interestwithin the display.

4.2.6.4 Display design

The SCADA system comprises of many displays ofwhich the displays which represent the power system(Single line diagram and the network diagram) are tobe customized as per the requirements of the user.

The standard meanings for colours (for examplemonitor displays, status lights) used at the UI tohighlight the condition of device monitored andcontrolled through control and data acquisitionequipment shall be defined by users. The significanceof colours shall be consistent throughout the system.

The following may be specified for the power systemdisplays:

a) Colours for equipments at various voltagelevels;

b) Symbol to be used for denoting variousdevices. A set of graphic symbols shall be partof the system. The capability to createadditional graphic symbol and graphics by theuser is to be provided;

c) Device highlighting in case of alarmed/abnormal state;

d) Presentation format of measurement (Unit,decimal places, directional arrow, colour);

e) Presentation of alarm (priority identification,colour, acknowledgement);

f) Information required in each layer of adisplay;

g) Organization of display; andh) Information available on each display.

4.2.6.5 Type of displays

The types of displays required in the SCADA systemare to be specified. The content and organization of

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the display shall conform to the users operationphilosophy. The following are the type of displays thatexist in the power utility system environment:

a) Power system displays:1) Single line diagram;2) Network display;

3) Station tabular display; and4) Equipment/Transmission line display.

b) Computer system displays:1) System configuration display; and

2) System performance monitoring display.

c) Communication display:1) RCCI communication display;2) Control centre communication display;

3) Communication equipment display; and4) Communication network monitoring

display.

d) User interface displays:

1) Navigation displays;

2) Directory display;3) Alarm displays;4) Event displays;

5) Exception displays;6) Summary displays — Alarm/Event/

Manual override/Off-normal/Out-ofscan/Alarm inhibit/Tag/Trending/Operator notes;

7) Reports and forms display; and

8) Help displays.

4.2.6.6 User interaction procedure

The sequential procedure for common user interactionswith the system shall be defined for each of the actions,such as the capabilities provided for operator inputs atthe user interface.

The user interaction capabilities may include acombination of the following:

a) Keys and switches (alphanumeric or function,or both);

b) Cursor (mouse, trackball, joy stick, or keycontrolled);

c) Light pen;

d) Poke points (defined monitor displayedcontrol selection fields); and

e) Pull down or pop up menus.

The user’s input to the UI equipment shall berecognized and acknowledged (valid or invalid) to theoperator within 0.5 s and confirm control actionswithin 2 s.

4.2.6.6.1 Interactive dialogue

The activity at the UI during interaction with theSCADA system shall be clearly described and shall beconsistent throughout the system.

The selection of a point for a user control action shallresult in a visual feedback at the user interface. Thispositive feedback to the user shall signify that theSCADA system is ready to accept a control action. Theresults of the control action shall be displayed onlyafter the actual change has taken place. The followingcontrol actions may be specified:

a) Control output options:

1) Enable/Disable;

2) Tagging (types and uses);

3) Local/Remote; and

4) Open (off)/close (on).

b) Control of data acquisition:

1) Enable/Disable scan (inputs or stations);

2) Enable/Disable processing;

3) Manual entry of data;

4) Change scan frequency by group;

5) Assign/Reassign data to a group; and

6) User defined interlocks.

c) Control of data processing:

1) Setting date and time;

2) Setting input change limits;

3) Defining formats;

4) Defining conversion data;

5) Defining operator override values; and

6) Defining normal/abnormal status/dataquality status.

d) Control of alarm processing:

1) Enable/Disable individual alarms;

2) Enter/Edit alarm limit value(s);

3) Enter/Edit alarm deadband value(s);

4) Enter/Edit return-to-normal criteria;

5) Enter/Edit alarm assignment to area ofresponsibility;

6) Enter/Edit alarm priority;

7) Acknowledge alarms (individual/page);

8) Silence audible alarm;

9) Inhibit alarms; and

10) Override invalid alarms.

e) Control of function checks:

1) Enable/Disable; and

2) Change frequency.

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f) Control of automatic control functions:1) Enable/Disable;2) Modify criteria;

3) Add/Delete control functions; and4) Reset to reference level or position.

4.2.6.7 Alarms

When alarm conditions are detected by the SCADAsystem, both an audible (Voice, tone, or bell) and visual(Flashing light or symbol) annunciation shall bepresented to the user. It shall be possible to silence theaudible alarm without affecting the visual annunciation.The visual indication of each alarm condition shallremain as long as the alarm condition exists. It shallbe possible to designate alarms as part of differentgroups, priorities and categories.

4.2.6.8 Trends

Trending is a display of series of values of parameterson a time axis. The SCADA system shall provide fordefinition of new collection of trends online. Trendscan be either of graphical type or of tabular type. Trendscan be obtained from real-time data (includingcalculated data) or historical data or bothsimultaneously. The following attributes of the trendshall be configurable:

a) Number of trend display;b) Number of parameters in a trend display;

c) Source of trend data — Historical data or real-time data or both;

d) Number of samples of each trended data;e) Trend rate (few seconds to minutes);

f) Trend duration (few hours to days);g) Number of Y-axis required, direction of scale

(unidirectional or bi-directional), Number ofscales, zero offset;

h) possibility of storage of the trend data, exportto text format;

j) Colour and graphical presentation (curve/trace/line/bar/pie chart); and

k) Graphical or tabular.

4.2.6.9 Operator notepad

An operator notepad allows a user to leave messageson a SCADA system display for information of theother users. It shall allow entering and editingmessages. The presence of a message on a display isindicated by an icon. The message can be called byselecting the icon.

4.2.6.10 Print function

Print function shall be specified to allow productionof hard copy of alarms, displays and reports. There are

various types of printers used in the control centre.Logger is a dot matrix printer which prints alarms (ifconfigured) as and when they occur in the system.Colour or black and white post script printers are usedfor printing of displays and reports. The applicablecharacteristics shall be defined as follows:

a) Display printing options:1) Full display or the selected display;2) Colour or black and white background;

3) Paper orientation;4) Identification of the operator console,

user and time of printing; and5) Application response time for printing.

b) Generation of log formats:

1) On-line/batch capabilities, and2) Symbols supported; and3) Spooling capabilities.

c) Demand logs:

1) Standard/Customized formats, and2) Time for response.

d) Logged activities:1) Alarms;

2) Standard events (for example, user anddevice actions);

3) System events (for example equipmentfailover and communication failure) ; and

4) Output from diagnostic routines.

e) Device performance:

1) Print speed (characters per second/pagesper minute);

2) Print quality (dots per inch); and3) Colour requirements.

f) Device assignments:

1) Initial;2) Automatic reassignment;3) Manual reassignment; and

4) Redundancy and failover.

4.2.6.11 Video projection system display

Video projection system (VPS) sometime called videowall is often used in a control centre to project anoverview of the power system which provides theoperators with a summary of the controlled powersystem. The VPS consists of a controller which isconnected to the SCADA system LAN and projectsthe display on the VPS screen. The VPS looselyintegrates with the SCADA system and hence therequirements are to be clearly defined and tested. Thefunctional and performance requirements of the

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display are similar to that of an operator workstationconsole.

4.2.6.12 Digital displays

Digital displays are used for projecting parameters likesystem time, day, frequency etc. which are prominentlydisplayed in the control centre. If digital displays areprovided the following needs to be specified:

a) Format and numeric range with decimal;b) Update frequency;c) Source of data — SCADA;

d) Size of display characters; ande) Brightness.

4.2.7 Historical Data

It is often felt necessary to store the real-time dataavailable in the SCADA system for purpose of analysisand report generation.

The different types of historical data storage which maybe required are:

a) continuous recording;b) data storage for report generation; and

c) alarm/event/log data storage.The requirement of storage of data in RDBMS(Relational database management) and its subsequentretrieval is generally handled by a separate system thanSCADA which requires independent hardware andsoftware.

4.2.7.1 Continuous recording (CR)

The continuous recording of data records all significantchanges in the power system data which can be usedfor future analysis. The continuous recording functioncollects and stores all the data (Analog and statusvalues) as and when the values received in the real-time SCADA database varies from its previous valueby a certain dead-band. The CR data can then beretrieved on the SCADA system displays or exportedto a RDBMS for reporting and viewing purpose.

4.2.7.2 Data storage and report generation

Power system data can be sampled from the real timedatabase at different periodicities and can be stored ina RDBMS for the purpose of report generation.

4.2.7.3 Alarm/Event/Log data storage

The alarm/event/log data may be stored forinvestigating the occurrences in SCADA system. Thestorage shall be such that it is possible to have extensiveanalysis like search and sort on the stored dataincluding sorting on basis of time, device, device type,priority and event.

The following shall be defined when the capability for

historical data archiving and retrieval is included asfollows:

a) Type of data to be stored;b) Volume of data (number of parameters);c) Data sampling intervals;

d) Number of data sampling intervals;e) Stored data review/modification;f) Online data retention time for different type

of data(days/week/month/year);

g) Stored data redundancy (RAID storage);h) Method of data archiving/retrieval (Tape/

Optical disk, automatic/manual );j) File maintenance procedure;

k) Data usage (for example displays, reports,applications); and

m) Type of reports/periodicity of reports/calculations to be performed.

4.2.8 SCADA System Redundancy

Redundancy can be specified in both the SCADAsystem and the RCCI, if high availability of thecontrolled system is required.

4.2.8.1 Redundancy in the RCCI

The redundancy in the RCCIs is generally limited tothe redundancy in communication ports centralprocessing unit (CPU) and the power supply. However,if required redundancy in I/O inputs can also bespecified to ensure high availability. The RCCIspreferably shall have redundancy of communicationports, power supply and CPU.

4.2.8.2 Redundancy in the control centre computersystem

The components (hardware/software) of the SCADAsystem can be duplicated so that even if one of theredundant components fails, the SCADA system shallremain available. In a redundant configuration ofservers, one server is in primary mode and other instandby or backup mode. The process of transferringthe role of a primary server to a backup server is calledfailover.

The following characteristics shall be defined whenredundancy in servers/facilities has been specified:

a) Type of redundancy:1) N+1 or 1+1 redundancy in hot standby

mode.

b) Database backup:1) Data residency (bulk or main memory);

and2) Frequency of backup (by data type)

ranges from 10 to 30 s.

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c) Database update:1) Data residency (bulk or main memory);

and2) Frequency of update (by data type)

ranges from 10 to 30 s.

d) Failure monitoring:

1) Method of failure detection (number offailed communication attempts,watchdog etc.);

2) Response time for detection — rangesfrom 4 to 10; and

3) Effect on a programme or task in progresswhen failover occurs.

e) Failover:

1) Method of failover (failover to redundantserver, restart, etc);

2) Time required for failover (ranges from30 s to 1 min — more in case of databaseserver);

3) User interface response followingfailover (user interface shall always beavailable);

4) User actions following fail over;5) Effect on a programme or task in progress

when failover occurs (terminated,resumes, restarts etc);

6) Functions which are required to failover(non-critical functions may not berequired to failover); and

7) Interactions with other components in theSCADA system.

4.2.9 SCADA System Hardware Characteristics

The SCADA system consists of hardware likecomputers, local area network switches, routers,printers, modem, communication card, RCCI, etc. Thepresent trend in the SCADA industry is that except theRCCI, most of the hardware is a commercially availableproduct available from third party manufacturers.

The choice of hardware is generally done by theSCADA vendors who prefer a particular hardwaremanufacturer/model based on the design of theirSCADA system. It is advisable to allow the SCADAvendor to do the hardware selection but only from offthe shelf hardware products.

However the following characteristics of the hardwareequipments may be specified to take care of future userrequirements:

a) Performance — CPU utilization/memoryutilization under peak/normal activitycondition;

b) Expandability — Processors/memory/Auxiliary memory;

c) Number of LAN interfaces;

d) Co-residency of applications — separateservers for each function;

e) Resolution and size of monitors;

f) Type of removal storage/mass storage device;

g) LAN equipment shall have suitable numberof spare ports (100 percent);

h) RCCI communication equipments shall havespare (100 percent) interfaces;

j) Performance of Printers — Resolution/ppm/duty cycle;

k) EMI/EMC compatibility;

m) Environmental requirements (Temperature/Humidity/Altitude);

n) Power supply and earthing requirements;

p) Statutory requirements like for environment,if any;

q) Power supply redundancy in the hardware;

r) Mounting and erection requirements;

s) Cabling requirements; and

t) Noise level.

It shall be the objective to purchase hardware which isthe current industry standards so availability of sparescan be guaranteed for a longer duration and alsosupport is available from the OEM.

4.2.10 Third Party Interface

The SCADA system generally stores and processes datain a proprietary format therefore means shall beavailable to access data from the SCADA system bothfor the real-time data and historical data. The standardinterfaces like ODBC/ DDE/SQL especially for thepersonal computer applications shall be specified asthis allows data to be imported in an environment towhich they are more familiar and allows betterutilization of the data. Also, there may be other systemsin the utility which need to exchange data with theSCADA system.

The requirement of programmable API’s (Applicationprogramming interface) can also be specified. TheseAPI’s are published by the SCADA system vendors toallow their program to interface to a third partyapplication.

4.2.11 Maintenance Facilities and Tools

The design of the SCADA system shall be such that itshall allow easy development, maintenance andoperation. It is advisable to have a separate system forperforming the development activities.

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The maintenance activity in the control centre includesthe following:

a) Database development and maintenanceactivity;

b) Display development and maintenanceactivity;

c) Reports/Forms development and maintenanceactivity; and

d) Application development and maintenanceactivity.

The maintenance activity in the RCCI includes thefollowing:

a) RCCI database configuration; andb) RCCI diagnostics.

The database and display development tools aregenerally proprietary.

4.2.11.1 Database development

The SCADA system has different types of databasesuch as development (modelling) databases, run-time(real-time) database and historical database. Thedatabase development tools requirement such as thefollowing may be specified:

a) Single source for modelling database of allcomponents of SCADA system;

b) Characteristics of source database —expandable without requiring software codechanges;

c) Hierarchical control centre setup requirementslike single point of source databasemaintenance;

d) Symbolic access to database;

e) Resize the entire database, redefine thestructure or any portion of the database;

f) Full graphics user interface;g) Import and export utility for bulk population

of database;

h) Multiple user access to databasesimultaneously with record level protection;

j) Database interactions like locate, order,retrieve, update, copy, insert and delete;

k) Type of changes to be done online and offline;

m) Database validation, referential integrity,reasonability and integrity checks;

n) Generation of error messages for helping user/extensive help regarding each activity;

p) Run-time database generation-incremental/complete;

q) Data retention — Data which is to be retainedacross database generation cycles;

r) Database on lining methods, timerequirements, archiving of previous run-timedatabase; and

s) Tracking database changes.

4.2.11.2 Display development

The displays development tool shall support thedevelopment and generation all types of displays inthe SCADA system. The following requirements forthe development tools may be specified:

a) Develop display elements, link displayelements to the database via symbolic names,establish display element dynamics viadatabase linkages, combine elements andlinkages into display layers, combine displaylayers into displays;

b) Types of display such as tabular, graphical,multi-page, multi-layered displays, worlddisplays;

c) Definition of refresh rates, initial zoom sizeof display, point of focus of a display;

d) Support for types of symbols, displayelements, user interaction fields and displays,colours, fonts, formats graphical objects,pictures, poke points;

e) Support for static transformation of displayelements like rotation, scaling, flipping;

f) Support for dynamic transformation likeflashing, reverse video, changing graphicalattributes, changing symbol based on valueof the linked database object;

g) Automatic tabular generation from database;and

h) Support for creating the database fromgraphical topology. This need to be mutuallyagreed between the user and the supplier.

4.2.11.3 Reports/Forms development

The tools shall support all the following facilitiesrequired to generate and edit reports in the SCADAsystem:

a) Extensive help for guiding a user in buildinga basic report;

b) Defining reports parameters such as databaselinkages, report formats, report activationcriterion, report destination, retention periodof report;

c) Capability to format reports for workstationand printers;

d) Presentation format such as alphanumericdisplay, graphical display or alphanumericprinter format;

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e) Processing functions applied at the time ofreport generation such as summations andother arithmetic functions;

f) Capability to edit the report, repeat theinherent data calculations, saving the editedreport;

g) Capability to modify an existing report fordatabase linkages, modify its format and storeit as a new report;

h) Report generation periodicities;j) Capability to export the report in some

standard file format; andk) Capability to publish the report on Web server,

if desired.

4.2.11.4 Application development and maintenance

The user can specify the requirement of tools to developnew applications and maintain the existing applicationsin the SCADA system. The following characteristicsmay be specified:

a) Code management system for documentingand controlling revisions to all SCADAprogrammes;

b) Compilers, assemblers, linkers and loaders,symbolic debugger;

c) System integration for adding newprogrammes to the set of active software;

d) System generation for generating anexecutable object code of all software,database, displays and reports, batch files andinteractive procedures for complete systemgeneration;

e) Failure analysis programmes to produceoperating system and application programmestatus data for analyzing the cause of fatalprogramme failure;

f) Diagnostics for trouble shooting each of thecomponents of the SCADA system;

g) Auxiliary memory backup and restore facility;and

h) System performance monitoring software.

5 GENERAL CONSIDERATIONS FOR SCADASYSTEM

The SCADA system shall be placed in the utilityenvironment and required to interface with variousequipments. The control centre equipments likecomputer and peripheral devices are generally provideda controlled environment that is the temperature,humidity and purity is controlled within a specifiedrange. However, the RCCIs are kept in remote locationswhere the environment is uncontrolled.

The following requirements may be specified.

5.1 Enclosures

The computer and peripherals are generally mountedin their OEM enclosures/ventilated racks whereas theRCCI is mounted in metal enclosures. The enclosuresalso provide a first level of protection against theelectromagnetic disturbances. The equipmentenclosures, which are generally made of sheet metal,shall be suitable for the proposed environment.

a) Enclosures should conform to the relevant IPClassification tests as per IS 13947(Part 1);

b) Enclosure mounting requirements —Standalone/Wall mounted/ pole mounted;

c) Enclosure finishing requirements — Paintcoats, paint colour;

d) Enclosure dimension requirements;

e) Location of access doors, glass doors;f) Temperature/ventilation requirements;g) Humidity control requirements;

h) Terminal-block type and location andconnector requirements should be specifiedfor individual applications;

j) Cable entry locations, and special cablingrequirements;

k) Type of cables for each application, cable/wiring requirements;

m) Enclosure grounding connections; andn) Weight constraints at site, if any.

5.2 Grounding

The SCADA equipment shall not place a ground on afloating power source. Care shall be exercised to ensureground compatibility when grounded power sourcesare used. The code of practice for earthing may bereferred as given in IS 3043. The SCADA systemvendor’s recommendation on the grounding practicesshall also be considered.

5.2.1 Safety or Equipment Ground

The safety or equipment ground protects personnelfrom injuries caused by live conductors coming incontact with the equipment cabinet or enclosure. Theground conductor shall be bundled with the powerconductors, but be insulated from the power conductorsand from other equipment and conduit. The groundconductor is usually terminated in the cabinetenclosure, and grounded only at the same point thatthe electrical service or UPS neutral is grounded. Allcabinets and/or enclosures comprising any control ordata acquisition equipment shall be grounded togetherby means of a ground cable or strap.

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Any buildings or allied structures for keeping allcabinets and/or enclosures comprising any control ordata acquisition equipment shall be protected fromlightening and code of practice for protection againstlightening may be referred as given in IS 2309.

Additionally, metal decking or other electrical pathsshould be grounded only at the same point that theelectrical service or UPS is grounded. Safety orequipment grounds shall be established in accordancewith SP 30.

5.2.2 Signal or Instrumentation Circuit Ground

The signal or instrumentation circuit ground shall beconnected to an external ground at a single point sothat ground loop conditions are minimized. Theshielded wire, drain wire, and/or ground wire of input/output cables shall be terminated at one ground pointin each cabinet. These ground points shall beconnected together and connected to the facilityground. Caution shall be used to prevent inadvertentground paths from devices such as convenience outlets,conduit, structural metal, test equipment, and externalinterfaces.

A special caution on filtering is worth noting. If thenoise is shunted to the signal ground, then it becomesanother source of signal reference corruption.Sometimes separate power, noise, digital, and analogground buses are necessary. However, the requirementfor a single point safety grounding source shall alwaysbe met. A very important design rule is to keep all signalreference voltages, at all frequencies of operation, asclose to zero as possible (that is at zero voltage signalreference).

5.2.3 Electrical Ground

The station power source shall be grounded inaccordance with the standard.

5.3 Electrical Power

The electric power supply to SCADA equipment is tobe chosen from the type of power supply available inthe control centre and the sub-station. The controlcentre equipments are generally powered from 230Vac power supply and are powered by a UPS(uninterruptible power supply) to ensure regulated anduninterruptible power supply. The RCCI is poweredgenerally from the dc power supply available at thelocation.

Equipment operating on direct current shall beprovided with protection such that these do not sustaindamage if the input voltage declines below the lowerlimit specified or is reversed in polarity. Also theequipment shall have protection against the ac ripplesuperimposed on the dc power supply.

5.3.1 Control Centre

The control centre equipment shall be capable ofoperating without error or damage with the followingvariation in the power supply source 230 V ac singlephase or three phase + 10 percent and –15 percent at50 Hz + 3 percent.

5.3.2 Remote Station Equipments

Remote station equipment shall be capable of operatingwithout error or damage with one or more of the fol-lowing source voltage ranges:

a) 230 V ac single phase + 10 percent at 50 Hz+ 3 percent; and

b) 24/48/110/220 V dc nominal with +20 percentvariation.

5.3.3 Power Quality

Station power shall be of such quality (free from noise,spikes, etc) to be suitable for use as a source to elec-tronic equipment. The user and supplier shall both beresponsible for conditioning (as required) the electricpower for use by SCADA equipment. The one end ofac power supply to master station for SCADA systemshould be grounded with isolating transformer.

5.3.4 Internal Noise

The control and data acquisition equipment internallygenerated electrical noise, from 1 000 to 10 000 Hz,appearing on the power source terminals shall be lessthan 1.5 percent (peak to peak) of the external powersource voltage. This is measured into an external powersource impedance of 0.1 Ω minimum.

5.4 Data and Control Interfaces

Data and control interfaces consist of electricalinterconnections between control and data acquisitionequipment (RCCI) and the device being monitored andcontrolled. Two types of signal paths are defined asfollows:

a) Data paths — Inputs to data acquisition orsupervisory control equipment; and

b) Control paths — Outputs from dataacquisition or supervisory control equipment.

For each input (data) or output (control) path, varioussignal characteristics shall be defined to specify theinterfaces between equipment.

Data and control signal cabling, which are external tocontrol and data acquisition equipment (RCCI), are notspecified.

5.5 Communication

Communication interfaces consist of functional,mechanical, and electrical interconnections between

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the control and data acquisition equipment and thecommunication equipment. Generally thecommunication interface requirement is specified inthe communication protocol standards and is as perthe expected usage. The communication channelincludes PLCC, microwave, radio, copper cable, fibreoptic types, VSAT, etc.

5.5.1 Control Centre/RCCI Links

Signal interfaces between the control and dataacquisition equipment (RCCI) and the datacommunication equipment (for example a data modem)occur whenever the data communication equipment isnot packaged as an integral part of the control and dataacquisition equipment, as illustrated in Fig. 5.

Signal interfaces between the control and dataacquisition equipment (when the data modem is partof the control and data acquisition equipment) and acommunication channel are illustrated in Fig. 6.

The following may be specified for the communicationinterface:

a) Connectivity configuration such as point topoint/party line;

b) Redundant or single connectivity;c) Type of communication channels; and

d) Channel failure recovery mechanism.

5.6 Environmental Conditions

This clause contains a definition of the environment inwhich the SCADA equipment is required to operate.

There are unusual conditions that, where they exist,shall receive special consideration. Such conditionsshall be brought to the attention of those responsiblefor the application, manufacture, and operation of theequipment. Devices for use in such cases may requirespecial construction or protection. The user shouldspecify those special physical requirements that applyto specific locations. Examples:

a) Damaging fumes or vapours, excessive orabrasive dust, explosive mixtures of dust orgases, steam, salt spray, excessive moisture,or dripping water;

b) vibration, shocks, or tilting;c) Radiant or conducted heat sources;d) Special transportation or storage conditions;e) Space limitations;f) Power limitations;g) Communication limitations;h) Operating duty, frequency of operation,

difficulty in maintenance access;j) Altitude of the operating locations in excess

of 1 000 m;k) electromagnetic interference; andm) exposure to ultraviolet light.

5.6.1 Environment

The different factors affecting equipment placed in aspecific environment are listed here.

5.6.1.1 Ambient temperature and humidity conditions

Ambient temperature and humidity are defined as the

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interface interface

DTE — Data terminal equipment DCE — Data communication equipment

FIG. 5 SIGNAL INTERFACES BETWEEN CONTROL AND DATA ACQUISITION EQUIPMENT

AND DATA COMMUNICATION EQUIPMENT

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FIG. 6 SIGNAL INTERFACES BETWEEN CONTROL AND DATA ACQUISITION

EQUIPMENT AND COMMUNICATION CHANNEL

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IS 15953 : 2011

conditions of the air surrounding the enclosure of theequipment (or the equipment itself, if it uses open rackconstruction) even if this enclosure is contained inanother enclosure or room.

The requirements for temperature and humidity fordifferent type of operating location is given in Table 1.Generally only two types are sufficient howeverequipment subjected to temperature and humidityvariations outside of the two type classifications listedin Table 1 will require special consideration.

The following measures may be taken to control thehumidity and the temperature:

a) Low temperature — A thermostaticallycontrolled heater strip should be used in thecabinet enclosure or use wide temperaturerange equipment.

b) High temperature — A sun shield, some othercooling method, or wide temperature rangeequipment should be used in case of devicesplaced in open.

c) High humidity — Heater strips or specialshelters should be used.

d) Low humidity — A humidifier should be usedto maintain acceptable humidity levels.

5.6.1.2 Dust, chemical gas and moisture

Any requirements of special provisions for protectionsuch as presence of atmospheric pollutants can bemade, where necessary.

5.6.1.3 Altitude

The SCADA equipment shall generally be suitable foroperation at altitudes up to at least 1 000 m. Anyrequirements of special provisions need to be made,where necessary.

5.6.1.4 Ultraviolet (UV) light exposure

The user shall specify the expected level of exposureto ultraviolet radiation attributable to sunlight whereequipment is to be installed outdoors. Equipmentcabinets, paint finishes, and jacket material of anyexposed cabling shall be sufficiently treated to resist

damage or degradation due to UV exposure. The usershall supply information pertaining to the anticipatedaverage daily hours of direct exposure to sunlight.

5.6.2 Electromagnetic Interference (EMI) andElectromagnetic Compatibility (EMC)

The SCADA equipments shall follow design criteriaand recommend practices that will minimize theadverse consequences of exposure to EMI. Effectiveprotection can only be accomplished through acombination of adequate design and proper installation.The basic design goal for achieving protection fromEMI shall be that of keeping any abnormal voltage orcurrent, or both, out of the equipment cabinets.

The SCADA equipment shall be designed for EMI/EMC criteria in conformance with IEC 60870-2-1:19951 ) for minimum level 2 requirements for RCCIand minimum level 1 requirements for Control Centreequipments.

Equipment failures resulting from EMI damage shouldbe fail-safe. Logic designs should be such as tominimize the possibility of false or improper operationof field devices. Partial failures that do not disable theequipment but can reduce or eliminate security features,such as error checking in communication circuits, shallbe detected and cause the blocking of control outputsto prevent false operations of field devices.

The basic installation goal for achieving protectionfrom EMI shall be to minimize the exposure of allconnecting wires and cables. Power, signal, andcommunication circuits provide a path through whichEMI enters equipment. Circuits totally within aprotected building can generally be installed withoutregard to these external effects. These circuits may stillbe subjected to transients generated by the operationof solenoids and control relays. Circuits that areconnected to, or are part of, circuits not within a

Table 1 Operating Temperature and Humidity by Location(Clause 5.6.1.1)

Sl No.

Type Typical Location of the Equipment

Humidity Operating Range (Percent Relative Humidity)

Temperature Operating Range

Allowable Rate of Change of Temperature

°C °C/h (1) (2) (3) (4) (5) (6)

i) 1(a) In a building with air-conditioned areas 40 to 60 +20 to +23 5 ii) 1(b) In a building with air-conditioned areas 20 to 80 +16 to +32 5

iii) 2 In a building or other sheltered area without special environmental control

10 to 95 without condensation 0 to +55 20

iv) 3 Extremes outside the above User to specify User to specify User to specify

1) The current versions of the base standards of IEC 61000-4 serieswhich are referred in the IEC 60870-2-1(1995) standard may beused on basis of mutual agreement between the User and the Vendorkeeping in view the location of the equipment(for example BayRCCI).

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protected building should be installed in a manner thatwill minimize exposure.

When installation constraints result in a high degreeof exposure to EMI such as surges, supplementaryprotection such as spark gaps or surge limiters shouldbe considered.

The computer and microcomputer based equipment areexpected to perform their intended functions insubstations even when exposed to transientelectromagnetic interference.

The user should specify the EMI level for guarantee-ing proper operation of the SCADA equipment.Annex C gives the test requirements for a typicaltransmission sub-station.

6 DESIGN CHARACTERISTICS

This clause defines general characteristics that arerequired of the control and data acquisition system.These characteristics include reliability,maintainability, availability, security, expandability,and changeability.

6.1 Reliability

The SCADA system reliability is while impacted bythe configuration of the hardware but actuallyencompasses the broader issue of system’s capabilityto perform intended work continuously. For example,a system can not be considered to be reliable if dataacquisition gets disturb in case of sudden burst ofactivity. Mathematically, reliability is the probabilitythat system will perform its intended function underspecified conditions during a specified period of time.For individual equipment, failures will occur on theaverage at a constant rate throughout the useful lifeof the equipment. This allows the manufacturer tocharacterize equipment reliability with a simplefigure of merit called mean-time-between-failure(MTBF).

The failure modes of equipment and the effects of thesefailures on overall system shall be formally analyzedby the supplier. The results of these failure modes andeffect analysis (FMEA) shall be available for reviewupon request.

6.2 Maintainability

Maintainability is the extent to which user’s personnelcan maintain the system both software and its hardware.Control and data acquisition equipment shall bemaintainable on-site by trained personnel accordingto the maintenance strategy specified by the user.Requirements for training, documentation, spares, etc,shall take the user’s organization and geography intoaccount.

It is the degree to which the configuration minimizesmaintenance requirements and supports and easilyreplaceable components. The most common repairstrategy is for the supplier to train the user’s personnelin problem isolation and replace faulty modules/components on-site from the user’s stock of sparemodules. If on-site service by the supplier is necessary,it is most likely to be required for failures of complexcomputer equipment.

The supplier shall, upon request, be required to provideas part of the system proposal, a list of test equipmentand quantities of spare parts calculated to be necessaryto meet the specified availability and maintainabilityrequirements. In establishing the quantities of spareparts, the supplier shall consider the time required toreturn a faulty component (field and/or factory serviceas the case may be) to a serviceable condition.

Mean time to repair (MTTR) is the sum ofadministrative, transport, and repair time.Administrative time is the time interval betweendetection of a failure and a call for service. Transporttime is the time interval between the call for serviceand on-site arrival of a technician and the necessaryreplacement parts. Repair time is the time required bya trained technician, having the replacement parts andthe recommended test equipment on-site, to restorenominal operation of the failed equipment.

6.3 Availability

Availability (A) is percentage of the time during whicha system is actually available to users and is defined inthe following as the ratio of uptime to total time(Uptime + Downtime):

A = Uptime/(Uptime + Downtime)

Downtime normally includes corrective and preventivemaintenance. When system expansion activitiescompromise the user’s ability to operate device via thesystem, this shall also be included in downtime.

Proper use of redundant configurations with automaticfail over can provide an overall availability of primarysystem functions of 99.9 percent.

The availability level required and the plannedmaintenance strategy shall be specified by the user,requiring suppliers to provide supporting predictedavailability calculations in their proposals.

An availability test of 1 000 to 3 000 h is often specifiedprior to acceptance of a system. For design analysis,and to determine the prediction of availability forsubassemblies and units, the following equationutilizing MTBF and MTTR shall be used:

Ap = MTBF/(MTBF + MTTR)

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Where Ap is predicted availability.

Equations for modelling complex designs shall be partof supplier proposal and agreed upon. The impact ofthe outage of each system element or function on theavailability of the total system shall be mutually agreedupon between the user and the supplier.

Major component downtime shall be defined to reflectthe proportional significance of the equipment that isdown. For example, downtime for the data acquisitionsystem could be defined as master station downtime,in proportion to the sum of the downtime for all RCCIsdivided by the total number of RCCIs. At the masterstation, downtime should not include malfunctions inperipheral devices that do not detract from thefunctional capabilities of the master station as a whole(for example, printers and tape units).

6.4 System Security

System security is defined as controlled access tosystem resources, such as functions, data, andhardware. The security is based on,

a) establishment of the identity and authenticityof user before allowing interaction withsystem;

b) the access is extended based on the rightsdefined for the user in system;

c) data being stored/transmitted throughcommunication is protected against change;and

d) system shall log and monitor all eventsconsequential to security.

The security device and infrastructure deployed needsto ensure that only authorize users are allowed tointeract with system, there is identification and isolationof unauthorized accesses and there shall be logging ofall the events related to security for future analysis.

6.5 Expandability

Expandability is the ease with which new RCCI, newpoints and/or functions, or both, can be added to thesystem, with minimum or no downtime.

Expansion can be identified as addition of similar boxesto increase capacity of performing a function oraddition of component in existing boxes or adding newdevices/processor/servers to increase functionality.Expandability can be achieved by spare capacity, wiredcapacity and space-only. Spare capacity is capacity thatis not being utilized but is fully wired and equipped.Wired capacity is the capacity for which all commonequipment, wiring and space are provided, but no plug-in point hardware is provided. Space-only capacity isthe capacity for which cabinet-space-only is providedfor future addition of equipment and wiring.

Expandability limitations may include, but are notrestricted to the following:

a) Available physical space;b) Power supply capacity;c) Heat dissipation;

d) Processor throughput and number of processors;e) Memory capacity of all types;f) Point limits of software, or protocol;

g) Bus length, loading, and traffic;h) Limitations on routines, addresses, labels, or

buffers; andj) Unacceptable level of performance (for

example extension of scan times) by increaseddata (given bit rate and protocol efficiency).

6.6 Changeability

Changeability is defined as the ease with which system,RCCI, and point data base parameters may be changedat both the master station and RCCI. Parameters thatshall be easy to change include the following:

a) Operating parameters; andb) Configuration and set-up parameters.

The supplier’s documentation (see 8.3) shall containthe step-by-step process for parameter changes.

6.6.1 Operating Parameters

Operating parameters must be easily changed by thesystem user. They include, but are not limited to, thefollowing:

a) RCCI on/off scan;

b) Point on/off scan;c) Point tags on/off;d) Manually entered values;

e) Point alarm limits; andf) Point dead band values.

6.6.2 Configuration and Set-up Parameters

Configuration and set-up parameters must be easilychanged by an authorized system engineer, but shallbe protected against being changed by the operator.They include the following:

a) Configuration password;b) Alarm conditions and actions;

c) User-definable calculations;d) Definition of a new RCCI including RCCI

database points;e) Correspondence of status points to control

points;

f) Point scaling factors for conversion of datato engineering units; and

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g) Output relay delay times.

6.6.3 Changeability Limitations

Changeability limitations may result from, but are notlimited to, the following:

a) Inability to make master station and RCCI database changes on-line from the master station;

b) Storage of parameters in memory (forexample ROM) that is not modifiable in-circuit;

c) Restrictions caused by data base structure;

d) Hardware/software compatibility;e) Hardware limitations;f) Software operating system limitations; and

g) Restrictions caused by use of IEDs.

The supplier shall declare all these limitation upfrontas part of its proposal.

6.7 Spare Memory

Spare memory is defined as the additional computermemory capacity that can be added to the masterstation. A requirement of no less than 50 percent unusedmain and auxiliary memory shall be delivered to takecare of moderate expansion of power system. As aminimum, it shall be possible to double the main andauxiliary memory delivered initially with the additionof modules.

6.8 Marking

The control and data acquisition equipment and majorsub-assemblies shall be suitably marked for safety andidentification. Each type of equipment shall beidentified so that it can be easily correlated with thedocumentation. The means of identification (forexample colour coding, labelling, and part number)shall be uniform throughout the system. Theidentification mark shall be permanently affixed to thepart that it identifies.

7 TESTS AND INSPECTIONS

The purpose of this clause is to describe the tests andinspections recommended to ensure that control anddata acquisition equipment will perform reliably andcorrectly according to the user’s technical specifica-tions. Test requirements shall cover, as a minimum, allcritical portions of the specification, especiallyfunctional, design, configuration, user interaction andexpandability requirements. Test results and alldeviations from test plans shall be required to bedocumented.

7.1 Stages of Tests and Inspection

The test and inspection process requires that various

functions of the equipment be tested or verified duringone or more stages in the production and installationcycle of the equipment. These stages and appropriatetests are illustrated in Table 2.

Across the top of the table are shown the four majorclasses of tests and inspections, being interface, envi-ronmental, functional and performance. The threestages of testing and inspections, being certified design,factory and field, are shown along the left-hand edgeof the table. The specific tests and inspections in eachclass are listed in the body of the table, below the classheading. Tests listed without notation are recommendedfor all applications at the stage they can be performed.

Tests marked with an asterik are optional and areperformed only when specified by the user. Certifieddesign tests on equipment can be accepted at the user’sdiscretion.

7.1.1 Certified Design Tests

These are tests performed by the supplier on specimensof a generic type of production model equipment andsystem to establish conformance with its designstandard. The conditions and results of these tests shallbe fully documented and certified.

7.1.2 Factory Tests and Inspections

This stage includes all functional tests and inspectionsperformed on the actual equipment to be supplied tothe user prior to the shipment of that equipment fromthe supplier’s facilities. The factory tests shall be ahighly structured procedure designed to demonstrate,as completely as possible, that the equipment willperform correctly and reliably in its intendedapplication. Factory tests may also include tests toverify some of the results of the certified design tests.

7.1.3 Field Tests and Inspections

Field tests and inspections are performed on theequipment in its operating environment. These includepre-installation inspections and tests to ensure theequipment has not been damaged during shipment andpost-installation tests to verify the equipment performsits functions reliably and correctly.

7.2 Interface Tests and Inspections

These tests are designed to demonstrate that the variousphysical and logical interfaces to the equipment are inaccordance with applicable portions of 5, together withother applicable parameters called out in the user’sspecifications with simulated communication/connection medium which will be agreed betweenowner and the supplier.

7.2.1 Mechanical

Mechanical characteristics (for example materials,

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IS 15953 : 2011

workmanship, dimensions, fabrication techniques andfinishes) shall be verified through visual inspectionsand comparisons with applicable drawings.

7.2.2 Electrical

These tests include all those to be performed onelectrical interfaces to the equipment, with theexception of those related to the functionalperformance of the equipment.

7.2.2.1 Power source

The equipment shall be tested to demonstrate the properoperation of the equipment throughout the range ofspecified power source parameters.

7.3 Environmental Tests

These tests are designed to demonstrate that theequipment will perform correctly and reliably whileexposed to the applicable environmental parametersdescribed in 5 , together with other applicableparameters called out in the user’s specifications. Theresults of certified design tests are usually sufficient todemonstrate that the equipment will operate reliablyand correctly within a specified environment. The usermay require the supplier to perform factory tests onthe equipment to demonstrate that it will indeedperform correctly under the specified environmentalconditions. Equipment in environmental tests shouldbe operating with realistic inputs and outputs.

The environmental parameters (EMI/EMC,temperature, humidity and dust) and testingrequirements specified by the user should be limitedto the worst case conditions that can be realisticallyanticipated in the location where the equipment willultimately be installed. See IS 9000 series for variousenvironmental tests.

7.4 Functional Tests

Functional tests shall be designed to ensure that the

equipment performs its functions reliably and correctly.They are performed during the factory, or field teststages, or both. Preliminary testing should beperformed by the supplier before verification by theuser. For many applications and types of equipment,successful factory tests will be a sufficient basis foracceptance of the system by the user. For more complexapplications or systems, additional tests in the field maybe required to fully verify correct and reliableperformance.

The following functional tests should be carried out:

a) Interface of RCCIs with IEDs;

b) End to end testing for database and alarmsvalidation;

c) Remote workstation testing;d) Remote control testing;

e) Checking of reports, archiving and trendingfunctions;

f) Clock synchronization between the nodes ofmaster station and RCCIs;

g) Security/Passwords testing;

h) Communication protocol testing; andj) User interface testing.

7.4.1 I/O Equipment Checkout

All I/O equipment being supplied shall be exhaustivelytested to demonstrate its functions. These tests shallbe performed with equipment that simulates the actualinputs/outputs to be monitored or controlled in case offactory. Field environment may not always be suitablefor testing process outputs.

7.4.2 Communication

The communication tests shall demonstrate properoperation of the equipment’s communicationcapability, including modems, security checking, andmessage protocols. The data modems or signalling

Table 2 Test Stages and Classes of Tests(Clause 7.1)

Classes of Tests Sl No.

Test Stages

Interface Tests and Inspections

Environmental Tests and Inspections

Functional Tests and Inspections

Performance Tests and Inspections

(1) (2) (3) (4) (5) (6)

i) Certified design tests

Power input* EMI/EMC Temperature Humidity

— —

ii) Factory tests and inspections

Mechanical power source*

Temperature* Humidity* Dust*

I/O point checkout communications user interface special functions

Loading Data acquisition Control User interface Computer and disk stability* Maintainability* Expandability*

iii) Field tests and inspections

Connectivity to existing system and field devices

— I/O point checkout communications user interface selected functions

Loading and availability

* Optional tests performed only when specified by the user.

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IS 15953 : 2011

equipment shall be exercized to verify that they operatecorrectly and reliably on the type of channel for whichthey are designed, under given signal to noise ratio.The tests shall be conducted under conditions thatduplicate, as closely as possible, the specifications forthe channel including simulated channel noise,communication failures and recovery.

The communication tests shall exercise all messageprotocols and formats to which the equipment isdesigned to respond. The tests shall also demonstratethat any error detection or correction capabilities func-tion properly and that the equipment does not respondto erroneous commands.

7.4.3 User Interface (UI)

Comprehensive user interface tests shall be performedto verify the correct functional operation of all userinterface hardware and software. All indications anddisplays shall be verified to ensure that they correlatewith the correct I/O of field equipment, and all usercontrols shall be checked to ensure that they result inonly the correct sequence of operations.

7.4.4 Special Functions

When the equipment supplied is to perform functionstailored expressly to the user’s application (for exampleclosed loop control), these functions shall be checkedappropriately. It is often necessary to perform thesetests in the field, in addition to factory testing.

7.5 System Performance Tests

The performance parameters of all critical componentof the system (for example communication,peripherals, user interfaces, I/O processing, and CPU)shall be measured under various loading conditions orscenarios. System performance shall be measured asearly as possible in a project to identify any systemweakness. This will allow the user and supplier anopportunity to resolve problems in a timely manner.

The loading scenarios shall simulate the following:

a) Normal activity — Initial system;

b) Heavy activity (disturbance loading definedby user) — Initial system; and

c) Communications failures or high noiseconditions such as high noise on an entiremicrowave system.

Loading conditions should be determined by analyzingworst case conditions experienced by the user and theworst possible condition likely to happen in the futureover the life of the system. Table 3 is provided as aguide.

The measurements for performance assume that allfunctions of the system have been individually verified

by functional tests and that the total system is ready tobe evaluated.

If actual system inputs are not available, they shall besimulated with special hardware or software. For ameaningful test, these inputs shall include the following:

a) Simulated RCCI/process inputs (alarmcontacts, analog inputs, status input, etc);

b) Simulated message data structures from theRCCIs into the master station communicationinterfaces;

c) Simulated data links to other computers,specifying the amount, type and frequency ofdata to be transferred;

d) Simulated user interfaces such as wall mimic;and

e) Other simulated inputs.

Table 3 System Performance Tests1)

(Clause 7.5)

Sl No. Input Activity Cycle (1) (2) (3)

i) Normal activity: a) Each user b) Status input c) Analog inputs

1 display request/min 1 percent changes/scan 1 percent of all analogs change/scan

ii) Heavy activity: a) Each user b) Status inputs c) Analog inputs

4 display request/min 10 percent changes/scan 25 percent of all analogs change/scan

1) Values given are for example only. It is recommended that theuser select values that represent the user’s system characteristicsand operating procedures.

Manual operation sequences to be performed during tests shall bedescribed in detail to provide a repeatable test scenario and a wayto measure improvements in performance (for example five peoplerequesting one-line diagrams and two people requesting menudisplays simultaneously). Test steps should simulate all normaluser operations.

Response performance shall be measured in seconds. Allmeasurements shall be recorded for analysis after the tests.Software utility programmes are available from most systemsuppliers for finding CPU utilization and loading (for example,feature of the computer operating system or a separate programmeavailable from computer manufacturer, or both) and if used bysupplier the system loading of the programs shall be provided touser with proof. Automatic measurement of other test parameterscan be done by special purpose software.

7.5.1 Data Acquisition Performance

Data acquisition sub-system performance measures thefollowing:

a) The time for a status change or analog changeat the RCCI to be displayed to the user at themaster station (for example, monitor, loggeror mimic); and

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IS 15953 : 2011

b) The time to query all RCCIs on a channel.

A cyclic status point input of 2 or more times fasterthan the system RCCI scan rate can be used to detect amissed scan due to overloading. The status inputsimulator should be connected to an input of one RCCI.The alarm associated with the toggled input shallappear on the logger with a time tag of approximatelytwice the scan rate. A system overload causing anextension of the scan cycle is obvious from the printoutbecause one or more status changes are missed.

7.5.2 Control Performance

Control performance measures the elapsed timebetween a control request by a user at the master stationand the control output contact closure at the RCCI.This test shall also be performed in the field. The fieldtest will provide realistic measurements, using userinstalled RCCIs and communication facilities.

7.5.3 User Interface Performance

The user interface performance is a measure of theresponse time to satisfy user requests for information.To measure display response time, measure the timefrom the instant a request is made until the result ofthe request is completely displayed on a UI screen,printed on a logger, or shown on a mimic panel.Different classes of displays (one-line diagrams, alarmsummaries, menus, tabular, etc) may have differentdisplay response times due to the amount of data to begathered and computations required before a displayrequest can be completed.

7.5.4 Computer and Disk Performance

The computer and disk performance shall be checkedagainst the user specified limits using the suppliedprograms from computer manufacturers to ascertainthat CPU and disk utilization is within acceptable limitas specified by user.

7.5.4.1 Computer link response time

Computer to computer link response times should bemeasured and evaluated during performance tests undervaried loading conditions.

7.5.4.2 Computer LANs utilization

Loading on LANs that connect application computerstogether should be measured and evaluated duringperformance tests.

7.5.4.3 Equipment reconfiguration, power fail andrestart tests

On systems with redundant equipment, reconfigurationtests should be performed to confirm the ability tofailover from one CPU/power supply to another(reconfigure the real-time database) and to switch

peripheral equipment to the primary system, thesecondary system, or off-line (that is out-of-service).

Power fail tests measure the time to recover from acomplete or partial power failure until the system isfully operational.

Restart tests are to assure the system will recover inspecified time from failures. Existing data shall consistof all scanned and manually entered data (that is values,system tags, manual overrides, limit changes, etc).

The time required to load a system from mass storageand initiate operation should be measured (cold start).

7.6 Test Run/Availability Test

An availability test takes place over a specified lengthof time during which the equipment shall operatecorrectly and reliably for at least a specified percentageof that time. The length of the test shall be mutuallyagreed to between the supplier and the user.

The availability test shall be run under conditionsmutually agreeable to the user and the supplier. Ingeneral, the supplier shall be responsible for makingthe necessary repairs. Downtime should not includedelays over which the supplier has no control.

This is followed by analyzing the number and types offailures, and their effects on system operation. The testtime should be selected so that the total number ofdevice operating hours for each type of system-criticaldevice is representative of the predicted MTBF for thatdevice to obtain statistically significant failure data.Specific rules for accumulation of uptime, downtime,maintenance time, and administrative time shall beagreed upon before the test (see 6).

7.7 Maintainability Test

The user shall require a maintainability test to be runto evaluate the supplier’s design, documentation, train-ing, and recommended spare parts. Maintainability willdirectly affect the availability of the SCADA systemand therefore the reliability of the system (see 6.2).Computer hardware maintenance and long term repairsupport are difficult to evaluate without actualexperience. Discussion with other users regarding theirexperience is one way to acquire a certain degree ofknowledge about the maintainability of specificequipment and systems.

Software, database, and display maintainability is alsocritical to the successful operation of a SCADA sys-tem. Tests to be witnessed may include the following:

System generation tests (measure time tocompletely install system, and type/quantum ofmanual intervention required)

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IS 15953 : 2011

a) Database maintenance test shall include:1) Adding an alarm point;2) Deleting or changing text on an alarm

point; and

3) Changing an analog scale factor.

b) Display maintenance:1) A new one-line diagram should be added

and linked to the database (a specificexample in the specification should beprovided); and

2) A line and new devices should be addedto an existing one-line diagram includinganalogs, tags, etc.

c) Equipment maintenance with spares beingsupplied as part of project for example

1) A monitor should be replaced;2) A modem should be replaced;3) A disk drive should be replaced;

4) A printer should be defines/added; and5) One card of each type shall be replaced

and/or added.

7.8 Expandability Tests

Expansion capability of a new system shall bedemonstrated during testing as specified (see 6.5). Forexample:

a) RCCI I/O point expansion (both hardware andsoftware changes required);

b) Addition of RCCIs; and

c) Master station expansion:1) Peripherals, disk space, memory;2) CPU capacity (percent utilization);

3) User interface (work station additions);and

4) Database and display expansion.

7.9 Documentation Verification

The final phase of the testing programme is to verifythat the documentation being supplied is an accuratedescription of the equipment, including all correctionsresulting from the tests. Final issue of completeddocumentation shall be provided as soon as possibleafter shipment and acceptance of the equipment.

8 DOCUMENTATION

The documentation for control and data acquisitionequipment shall cover five basic areas as follows:

a) Design;b) Installation;

c) Operating instructions and records;

d) Maintenance instructions and records; ande) Test (including quality assurance and quality

control test plans).In general, all final documentation provided by asupplier shall reflect the actual equipment as acceptedby the user, and all subsequent equipment changes shallbe recorded as document revisions by the user.

If users desire to have the information on reliability asdescribed in 6, they shall collect information on failuresand repairs for all sub-assemblies. This data onoperating performance shall then be periodicallyprovided to the supplier and can be basis for futureproduct/solution evaluation.

Documentation described in 8.1 through 8.5 may besubject to user review or approval. Documentation maybe structured in alternate fashion, but shall cover allfive areas. The documentation may be supplied in oneor more of several forms-printed, computer stored, orelectronic media. In the latter case, the supplier shalleither identify or supply the supporting wordprocessing software used to prepare the documentation.

8.1 Design Documentation

Design documentation is the responsibility of thesupplier. Block diagrams shall be included to describecontrol and data acquisition equipment and externalequipment. Layout and wiring drawings shall also beincluded to define external interconnection needs ateach facility. Text, photographs, and illustrativematerial shall accompany these drawings in sufficientdetail so that functional performance and design maybe readily understood. For example, functional blockdiagrams and explanatory text shall be used to describeeach major assembly and software programmecontained in the equipment configuration. A documentdescribing the communication process between themaster station and the RCCIs shall be provided. Thesupplier shall be responsible for providing outlinedrawings, mounting requirement details, customerconnection details, environmental requirements, size,weight, and any other information needed for the userto prepare for installation.

8.2 Installation Documentation

Installation documentation is the responsibility of boththe supplier and the user shall define the following:

a) Electrical power, data, control andcommunications interface wiring procedures;

b) Floor, rack and shelf mounting, drilling, andbolting methods necessary to secure theequipment in place;

c) Safety precautions or guards;d) Grounding and bonding procedures;

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IS 15953 : 2011

e) Clearances for access and ventilation;f) Testing and alignment methods;g) Weather proofing, dust proofing and other

environmental procedures; and

h) Other procedures needed to properly installthe equipment.

8.3 Operating Instructions and Records

Instruction information shall be developed foroperating personnel who use the control and dataacquisition equipment.

8.3.1 Operating Instructions

The supplier shall publish instructional informationdefining the equipment and how it shall be operated.The information shall consist of a general descriptionof the equipment configuration provided and shall stateits intended use and its major performancecharacteristics. Whenever a user interface such as aconsole, indicating/control panel or printing device isinvolved, the operational documentation shall detailstep required to use these interface devices. Adequateillustrative material shall be included to identify andlocate all control indications.

Procedural instructions, that state routine andemergency procedures, safety precautions, andquantitative and qualitative limits to be observed inthe starting, running, stopping, switching, and shuttingdown of equipment, shall be included. Wheneveroperating procedures or adjustments are to beperformed in a specific sequence, step-by-step instruc-tions should be stated.

8.3.2 Records

Records shall be prepared by both operating andmaintenance personnel to support the availability/reliability calculation defined.

8.4 Maintenance Instructions and Records

Maintenance documentation for skilled personnel asper agreed maintenance philosophy shall be developedand provided by the supplier, and shall include thefollowing information listed in 8.4.1 through 8.4.4.

8.4.1 Performance Information

This information shall include a condensed descriptionof how the equipment operates (derived from 8.1) anda block diagram illustrating each major assembly andsoftware programme in the configuration. Messagesequences, including data and security formats for eachtype of message, shall be included in the condenseddescription and illustrated whenever such messages areused between stations or locally at a station. Theoperational sequence of major assemblies and

programmes shall be described and illustrated byfunctional block diagrams. Detailed logic diagrams andflowcharts shall also be provided as necessary fortrouble shooting analysis and field-repair actions.

8.4.2 Preventive Maintenance Instructions

These instructions shall include all applicable visualexaminations, software and hardware test and diagnos-tic routines, and resultant adjustments necessary forperiodic maintenance of control equipment.Instructions on how to load and use any test anddiagnostic programme, and any special or standard testequipment shall be an integral part of these procedures.

8.4.3 Corrective Maintenance Instructions

These instructions shall include guides for locatingmalfunctions down to the spare parts replacement orfield-repair level. These guides shall include adequatedetails for quickly and efficiently locating the causeof an equipment malfunction, and shall state theprobable source(s) of trouble, the symptoms, probablecause, and instructions for correcting the malfunction.These guides shall explain how to use any on-line testand diagnostic programme and any special testequipment, if applicable.

Corrective maintenance instructions shall also includeexplanations for the repair, adjustment, or replacementof all items. Schematic diagrams of electrical,mechanical, and electronic circuits; parts location illus-trations, or other methods of parts locationinformation; and photographs, and exploded andsectional views giving details of mechanicalassemblies shall be provided as necessary to repair orreplace equipment. Information on the loading and useof special off-line diagnostic programmes, tools, andtest equipment, and any cautions or warnings whichshall be observed to protect personnel and equipmentshall also be included.

8.4.4 Parts Information

This information shall include the identification of eachreplaceable or field repairable module. Parts shall beidentified on a list or drawing in sufficient detail forprocurement of any repairable or replaceable part.These parts shall be identified by their industrial,generic part numbers and shall have second sourcereferencing, whenever possible.

8.5 Test Documentation

Test documentation by the supplier shall consist of asystem test plan, test procedures and certified testreports on tests described in 7. The test plan shall statewhat equipment configuration will be tested, when itwill be tested, which tests will be run, and who willconduct and witness the tests. The test procedures shall

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IS 15953 : 2011

define the operating steps and expected results. Thetest report shall record all test results.

9 SCADA SYSTEM IMPLEMENTATION ISSUES

There are certain issues which require a great deal ofattention while implementing a SCADA system:

9.1 Integration with Existing System

The utility may have existing set of equipments likeRCCIs or even a control centre. The requirements ofintegrating these equipments shall be specified. Atechno-commercial analysis has to be done beforehandso that the pros and cons of integrating the existingequipment can be worked out. Often it is felt thatintegrating an existing system requires lot of effort.This is especially more the case when the system to beintegrated is a proprietary system with no support forstandard communication protocols.

9.2 Training

The personnel who are to operate and maintain theSCADA system shall be identified and involved in theimplementation of the SCADA system from the initialstages. This provides an opportunity for the personnelto become familiar with the system and hence to use itmore effectively.

These personnel shall be provided extensive trainingabout the system. Generally the training requirementscan be classified as following:

a) RCCI;

b) Computer system hardware;c) Computer system software; andd) SCADA application software.

9.3 Spare Availability and Expandability

The SCADA equipments keep evolving with theinnovations in technologies. This causes obsolescenceof the equipments and the newer generation of thehardware may not be compatible with the existing

SCADA equipments. Hence, long-term agreementswith the supplier for the SCADA system can be madeeither for supply of spare parts for the expected life ofthe SCADA system or for maintenance of system.

Also with time, the SCADA system keeps on growingto accommodate the growing power system. However,as explained above, the components for achieving thisexpansion are not available even though provisions forexpandability are made in the system. Hence, it isadvisable to have an estimate of the ultimate systemsizing requirement and equip the SCADA system withall necessary components for this ultimate size. Theperformance testing of the SCADA system can be doneby removing these additional components.

9.4 Maintenance of the SCADA System

The SCADA system is an advanced, complex andproprietary information technology (IT) system whichrequires knowledge and skills of software, hardware,standards etc. Generally the utilities do not havepersonnel of high level of knowledge and skills in ITdomain. Also there are issues like obsolescence.Utilities have to decide whether they wish to take upthe maintenance activity of the SCADA systemthemselves or will enter into a long-term agreementwith the SCADA vendor for maintenance and upgradeof the system to maintain an evergreen SCADA system.If the maintenance is to be done through the SCADAvendor, this requirement shall be specified.

9.5 Customized Product versus SCADA VendorProduct

The utility shall specify only the functionalrequirements and shall refrain from specifying specifictechnology or procedures unless it is very critical totheir interest. Any customization requires an additionaldevelopment effort on the part of SCADA vendorswhich may not be carried over to the next version ofthe SCADA system. Hence customizations becomecostly to implement and maintain.

IS No. Title

1885 Electrotechnical vocabulary:(Part 50) : 1985 Telecontrol(Part 52) : 1980 Data processing

ANNEX A(Clause 2)

LIST OF REFERRED INDIAN STANDARDS

IS No. Title

2309 : 1989 Code of practice for the protectionof buildings and allied structuresagainst lightning (second revision)

29

IS 15953 : 2011

IS No. Title

3043 : 1987 Code of practice for earthing9000 : 1977 Basic environmental testing

procedures for electronic andelectrical items

12746 Telecontrol equipment and systems:(Part 1/Sec 3) : Part 1 General considerations,1993 Section 3 Glossary

B-1 The following Fig. 7 to 16 are informatory innature:

Master Station RCCI

FIG. 7 SINGLE MASTER STATION, SINGLE RCCI

Master Station RCCI 2

RCCI 1

RCCI N

FIG. 8 SINGLE MASTER STATION, MULTIPLE RCCI(S),RADIAL CIRCUIT

Master Station RCCI 2

RCCI 1

RCCI N

FIG. 9 SINGLE MASTER STATION, MULTIPLE RCCI(S),PARTY-LINE CIRCUIT

IS No. Title

14570 : 1998 Electrical measuring transducers forconverting ac electrical quantities toanalogue or digital signals

60947 (Part 1) : Low voltage switchgear and2004 controlgear: Part 1 General rules

SP 30 : 1985 National Electrical Code

ANNEX B(Clause 4.1.2)

MASTER STATION/RCCI INTER-CONNECTIONS

Master Station 1

RCCI 2

RCCI 1

RCCI N

Master Station 2

FIG. 10 DUAL MASTER STATIONS, MULTIPLE RCCI(S),LOOPED PARTY LINE

Master Station 1

RCCI

Master Station 2

FIG. 11 DUAL MASTER STATIONS, SINGLE DUAL

PORTED RCCI, RADIAL CIRCUIT

Master Station 1

RCCI 1

RCCI N

Master Station M

RCCI 1

RCCI M

FIG. 12 DUAL MASTER STATIONS, MULTIPLE RCCI(S)[SINGLE PORTED RCCI(S)]

30

IS 15953 : 2011

Master Station 1

RCCI 1

RCCI N

Master Station M

RCCI 1

RCCI M

FIG. 13 DUAL MASTER STATIONS, MULTIPLE RCCI(S)[DUAL PORTED RCCI(S)]

Master Station 1

RCCI 1

RCCI N

RCCI 1

RCCI M

Sub-Master Station

FIG. 14 SINGLE MASTER STATION, SINGLE

SUB-MASTER STATION MULTIPLE RCCI(S)

Master Station 1

RCCI 1

RCCI N

RCCI 1

RCCI N

Sub-Master Station 1

Sub-Master Station N

Sub-master stations could communicate with one another.

FIG. 15 SINGLE MASTER STATION, MULTIPLE

SUB-MASTER STATIONS MULTIPLE RCCI(S)

Master Station

RCCI 1 RCCI N

End Station

FIG. 16 SINGLE MASTER STATION, RCCI(S) AND

END STATION LINK

C-1 EMI/EMC AND ENVIRONMENT TEST LEVELS OF A TYPICAL TRANSMISSION SUB-STATION

Sl No. Test Name Passing Criteria

i) Surge Immunity Test (1.2/50µs) IEC 61255-22-5 ii) Electrical Fast Transient Burst Test IEC 60255-22-4

iii) Damped Oscillatory Wave Test IEC 61000-4-12 iv) Electrostatic Discharge Test IEC 60255-22-2 v) Radiated Electro-magnetic Field Test IEC 61000-4-3

vi) Damped Oscillatory Magnetic Field Test IEC 61000-4-10 vii) Power Frequency Magnetic Field IEC 61000-4-8

viii) Power Frequency Voltage Withstand IEC 60255-5 ix) 1.2/50µs Impulse Voltage Withstand IEC 60255-5 x) Insulation Resistance Test IEC 60255-5

xi) Dry Heat Test IEC 60068-2-2 xii) Damp Heat Test IEC 60068-2-3

NOTE — The IEC 61000-4-3: 2006 can be referred as base standard keeping in view location of RCCI.

ANNEX C(Clause 5.6.2)

TEST REQUIREMENTS FOR A TYPICAL TRANSMISSION SUB-STATION

31

IS 15953 : 2011

ANNEX D(Foreword)

COMMITTEE COMPOSITION

Power System Control and Associated Communications Sectional Committee, LITD 10

Organization Representative(s)

Power Grid Corporation of India Limited, Gurgaon SHRI R. N. NAYAK (Chairman)SHRI R. P. SASMAL (Alternate)

Areva T&D India Ltd, Noida SHRI SUDESH KUMAR NEHRU

SHRI VINAYAK NAYAK (Alternate)

ABB Ltd, Bangalore SHRI RAJIV KRISHNAN

SHRI S. R. VIJAYAN (Alternate)

Bharat Heavy Electricals Ltd, Hyderabad SHRI G. V. BANAKAR

SHRI B. K. CHATTAR (Alternate)

Central Electricity Authority, New Delhi SHRI D. K. JAIN

SHRI D. K. MALIK (Alternate)

Central Power Research Institute, Bangalore SHRI V. ARUNACHALAM

SHRI V. SHIVAKUMAR (Alternate)

Electronics Regional Test Laboratory (North), New Delhi SHRI ASHOK KUMAR

SHRIMATI MANJULA BHATI (Alternate)

GAIL (India) Ltd, New Delhi SHRI R. CHOUDHURY

SHRI TAPAN D. PARIDA (Alternate)

Gujarat Electricity Board, Vadodara REPRESENTATIVE

Kalki Communication Technologies Pvt Ltd, Bangalore SHRI PRASANTH GOPALAKRISHNAN

SHRI VINOO S. WARRIER (Alternate)

National Thermal Power Corporation Ltd, New Delhi SHRI ABIJIT SEN

Reliance Energy Limited, Mumbai SHRI HARSH SHARMA

SHRI BHUSHAN CHAUDHARI (Alternate)

Secure Meters Limited, Udaipur SHRI KAUSHIK GHOSH

SHRI SUNIL KUMAR SINGHVI (Alternate)

Siemens Ltd, Gurgaon SHRI VIKRAM GANDOTRA

SHRI GIRISH MULEY (Alternate)

Society for Applied Microwave Electronics Engg & Research, SHRI R. SIVARAMAKRISHNAN

Chennai DR B. SUBBARAO (Alternate)

TCE Consulting Engineers Ltd, Bangalore SHRI N. MURUGESAN

MS ANITA JOSHI (Alternate)

The Tata Power Company Limited, Mumbai SHRI JACOB JOSEPH

SHRI P. A. JAYAKUMAR (Alternate)

Transmission Corporation of Andhra Pradesh Ltd, Hyderabad SHRI M. GOPAL RAO

SHRI K. RAJAMANNAR (Alternate)

Wireless Planning & Coordination Wing, New Delhi REPRESENTATIVE

BIS Directorate General SHRI NARENDRA SINGH, Scientist ‘E’ and Head (LITD)[Representing Director General (Ex-officio)]

Member SecretarySHRI JITENDER KUMAR

Scientist ‘C’(LITD), BIS

32

IS 15953 : 2011

SCADA Working Group for Power Sector under LITD 10Organization Representative(s)

Power Grid Corporation of India Limited, New Delhi SHRI ARUN KUMAR MISHRA (Convener)SHRI ARUN KUMAR SINGH (Alternate)

ABB Limited, Bangalore SHRI RAJIV KRISHNAN

SHRI S. R. VIJAYAN (Alternate)

Central Electricity Authority, New Delhi SHRI D. K. JAIN

SHRI D. K. MALIK (Alternate)

Central Power Research Institute, Bangalore SHRI V. ARUNACHALAM

SHRI V. SHIVAKUMAR (Alternate)

Electronics Regional Test Laboratory (North), New Delhi SHRI ASHOK KUMAR

SHRIMATI MANJULA BHATI (Alternate)

Kalki Communication Technologies Pvt Ltd, Bangalore SHRI PRASANTH GOPALAKRISHNAN

SHRI JOSE THOMAS (Alternate)

Reliance Energy Limited, New Delhi SHRI HARSH SHARMA

SHRI BHUSHAN CHAUDHARI (Alternate)

Siemens Ltd, Gurgaon SHRI VIKRAM GANDOTRA

SHRI GIRISH MULEY (Alternate)

TCE Consulting Engineers Ltd, Bangalore SHRI N. MURUGESAN

Transmission Corporation of Andhra Pradesh Ltd, Hyderabad SHRI M. GOPAL RAO

SHRI K. RAJAMANNAR (Alternate)

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any formwithout the prior permission in writing of BIS. This does not preclude the free use, in the course ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of‘BIS Catalogue’ and ‘Standards : Monthly Additions’.

This Indian Standard has been developed from Doc No.: LITD 10 (3061).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

BUREAU OF INDIAN STANDARDS

Headquarters:

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002Telephones : 2323 0131, 2323 3375, 2323 9402 Website: www.bis.org.in

Regional Offices: Telephones

Central : Manak Bhavan, 9 Bahadur Shah Zafar Marg 2323 7617NEW DELHI 110002 2323 3841

Eastern : 1/14 C.I.T. Scheme VII M, V. I. P. Road, Kankurgachi 2337 8499, 2337 8561KOLKATA 700054 2337 8626, 2337 9120

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Documents

IS 15953 (2011): Supervisory Control and Data Acquisition