Ashwani kumar

SUBSTATION(A GENERAL VIEW)

NAME-ASHWANI KUMAR

ROLL NO-124011

CONTENTS

Abstract

Substation and Its types

Symbol For SwitchYard Equipment

SwitchYard Equipment

Protective Relays and Its types

SwitchYard Emergencies and Plan Of Actions.

ABSTRACT The power system network basically consists of three sub-

network - generation sub-network, transmission sub-network, distribution sub-network.

However due to any reason some fault occurs, these conditions become abnormal by increase or decrease in voltage , current & power factor becomes very high & poor or line flows become abnormally very high- it is necessary that there should be a device which senses these abnormal conditions

It is necessary to remove the abnormality because the power system components can never be designed to withstand the worst possible conditions, as it will make the whole system highly uneconomical.

SUBSTATION

Substations serve as sources of energy supply for local areas of distribution in which these are located

Main function is to receive energy transmitted at high voltage from generating stations, reduce the voltage to a value appropriate for local distribution and provide facilities for switching .

It also provides points where safety devices may be installed to disconnect equipment or circuit in event of fault

TYPES

High Voltage Substation – It operates voltages between 11KV and 66KV.

Extra High Voltage Substation – Involving voltages between 132KV and 400KV.

Ultra High Voltage Substation – Operating on voltage above 400KV.

Indoor Type Substation – Apparatus is installed within substation building which are usually for voltage upto 11KV, 33KV and 66KV.

TYPES (contd..)

Outdoor Substation – Subdivide into –

i. Pole Mounted Substation – Useful for distribution of power in localities. H-pole or 4 pole structure with suitable plateform is used for transformers of capacity upto 250KVA.

ii. Foundation Mounted Substation – For transformers of capacity above 250KVA. The transformers are too haevy for pole mounting . Such substation are usually for voltages of 33KV and above .

Typical Components of a Power Plant Substation (Switchyard)

•A - Busbar

•B - Disconnector

•C - Circuit Breaker

•D - Current Transformer

•E - Voltage Transformer

•F - Earthing Switch

•G - Surge Arrestor

• CONNECT

• CONNECT & DIS-CONNECT

• CONNECT, DIS-CONNECT & DETECT

• DETECT & TRANSFORM

• DETECT & TRANSFORM

• PROTECT & SAFETY

• PROTECT

SWITCHYARD EQUIPMENT

Circuit Breakers

Isolators

EarthSwitch

Bus bar

Surge / Lightening Arrestors

Current Transformer

Capacitive Voltage Transformer

Wave Trap

Post Insulator

Relay

CIRCUIT BREAKER

Circuit Breaker – it is an automatically operated electricalswitch designed to protect an elctrical circuit from damage caused byoverload or short circuit. Its basic function is to detect a fault conditionand interrupt current flow.

The operation of the breaker is very rapid when opening.

Working of circuit breaker- The circuit breaker mainlyconsists of fixed contacts and moving contacts. In normal “on”condition of circuit breaker, these two contacts are physicallyconnected to each other due to applied mechanical pressure onthe moving contacts. There is an arrangement stored potentialenergy in the operating mechanism of circuit breaker which isrealized if switching signal given to the breaker. The potentialenergy can be stored in the circuit breaker by different ways likeby deforming metal spring, by compressed air, or by hydrolicpressure.

WORKING OF CIRCUIT BREAKER(Contd…)But whatever the source of potential energy, it must be releasedduring operation. Release of potential energy makes sliding of themoving contact at extremely fast manner All circuit breaker haveoperating coils (tripping coils and close coil), whenever these coilsare energized by switching pulse, the plunger inside themdisplaced. This operating coil plunger is typically attached tothe operating mechanism of circuit breaker, as a result themechanically stored potential energy in the breaker mechanism isreleased in forms of kinetic energy, which makes the movingcontact to move as these moving contacts mechanically attachedthrough a gear lever arrangement with the operating mechanism.After a cycle of operation of circuit breaker the total storedenergy is released and hence the potential energy again stored inthe operating mechanism of circuit breaker by means of springcharging motor or air compressor or by any other means.

1. Actuator lever - used to manually trip

and reset the circuit breaker.

2. Actuator mechanism - forces the

contacts together or apart

3. Contacts - Allow current when

touching and break the current when

moved apart

4. Terminals

5. Bimetallic strip.

6. Calibration screw - allows the

manufacturer to precisely adjust the

trip current of the device after

assembly.

7. Solenoid

8. Arc divider/extinguisher

CIRCUIT BREAKER

TYPES OF CIRCUIT BREAKER

Air Circuit Breaker-

Arc is initiated and extinguished in substantially static air inwhich the arc moves.

Used for low voltages upto 15KV and rupturing capacities of500MVA.

Air Blast Circuit Breaker-

Blast of air is used to blow out the arc.

Air is stored in tank and released through a nozzle to producehigh velocity jet to extinguish the arc.

TYPES OF CIRCUIT BREAKERS(Contd..) Sulphur Hexafluoride(SF6) Circuit Breaker –

SF6 Under pressure is used to extinguish the arc.

SF6 gas have excellent dielectric, arc quenching ,chemical and other physical properties and is superior to other arc quenching mediums such as oil and air.

Vaccum Circuit Breaker – Fixed and moving contacts are housed inside a

permanenly sealed vaccum interrupter .The arc is quenched as contacts are separated in high vaccum .

It is more efficient,less bulky, cheaper in cost and longer life.

ISOLATOR

Isolator is a mechanical switch which isolates a part of

circuit from system for safe maintenance works.

It is a disconnection switch and to be operated on no

load.

It is used to make sure that an electrical circuit can be

completely de-energized for service or maintenance.

It provide electrical isolation of the equipment.

isolators must be open after circuit breaker is open and

these must be closed before circuit breaker is closed

otherwise arc would be produced results in power loss.

ISOLATOR

ISOLATOR WHEN OPEN ISOLATOR WHEN CLOSED

EARTH SWITCH

Earth switch is required to discharge the trapped charges on the line & consists of vertical break.

Earth switch can only be operated locally.

BUS BAR

The flow of electrical power between incoming and outgoing circuits takes place through the bus bars.

These are junction points carrying huge power’

These are copper rods or thin walled tubes operating at constant voltage.

TYPES OF BUS BAR

Types of Bus Bar Arrangement:

Single Bus bar Arrangement

Single Sectionalized Bus bar Scheme

Main & transfer bus bar scheme

Double Bus arrangement

Double bus and transfer bus arrangement

One and half breaker scheme

SURGE/LIGHTENIG ARRESTORS A lightning arrester is a

device used on electrical power systems to protect the insulation and conductors of the system from the damaging effects of lightning.

The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth.

SURGE/LIGHTENIG ARRESTORS

A Surge Arrestor is a voltage-sensitive device that it operates in principle, as a non-linear resistor.

If protection fails or is absent, lightning that strikes the electrical system introduces thousands of kilovolts that may damage the transmission lines, and can also cause severe damage to transformers and other electrical or electronic devices.

CURRENT TRANSFORMERS

Used for measuring high value currents.

Designed to provide a current in its secondary coil proportional to current flowing in its primary coil.

Primary winding consists of very few turns.

Secondary winding consists of large no. of turns.

Current to be measured is passes through primary winding.


A capacitor voltage transformer (CVT or CCVT), is a transformerused in power systemsto step down extra high voltage signals and provide a low voltagesignal, for metering or operating a protective relay.


Main applications of CVTs in HV Networks

Voltage Measuring: They accurately transform transmission voltages down to useable levels for revenue metering, protection and control purposes

Insulation: They guarantee the insulation between HV network and LV circuits ensuring safety condition to control room operators

HF Transmissions: They can be used for Power Line Carrier (PLC) coupling.

WAVE TRAPS Wave Traps are used at sub-

stations using Power Line Carrier Communication (PLCC).

PLCC is used to transmit communication and control information at a high frequency over the power lines.

This reduces need for a separate infra for communication between sub-stations.

WAVE TRAPS The Wave Traps extract the high

frequency information from the power lines and route it to the telecomm panels. They also block any surges from passing through.

Wave Traps are simply resonant circuits that produce a high impedance against Power line carrier communication carrier frequencies (24kHz - 500kHz) while allowing power frequency (50Hz - 60Hz).

POST INSULATORS

These provides necessary insulation between line conductors and supports and thus prevent the leakage of current from conductors to earth.

Insulators used for high-voltage power transmission are made from glass, porcelain or composite polymer materials.

Porcelain insulators are made from clay, quartz or alumina and feldspar, and are covered with a smooth glaze to shed water.

POST INSULATORS

Types of insulator-

1. Pin type insulator - The pin type insulator is mounted on a pin on the cross-arm on the pole and used for electric power at voltages up to 33 kV.

2. Suspension type insulator- For voltages greater than 33 kV, it is a usual practice to use suspension type insulators consisting of a number of glass or porcelain discs connected in series by metal links in the form of a string.

3. Strain insulator.

4. Shackle insulator – For low voltage levels .

How Substation Work

RELAYS

Relay- It detects the faulty element in the integrated power system and removes it with the help of circuit breaker from the remaining healthy system as quickly as possible to avoid the damage.

Main features-

Reliability .

Sensitivity .

Simplicity .

Speed .

Economy .

TYPES OF RELAYS

OVERVOLTAGE, OVERCURRENT AND OVERPOWER RELAYS-These relays operate when the voltage,current and power rises above a specified value .

UNDERVOLTAGE,UNDERCURRENT AND UNDERPOWER RELAYS-These relays operate when the voltage, current and power falls below a specified value .

DISTANCE RELAY-In this relay, the operation depends upon the ratio of voltage to current .

TYPES OF RELAYS(Contd…)

DIRECTIONAL OR REVERSE CURRENT RELAY –The relay operates when the applied current assumes a specified phase displacement with respect to applied voltage and relay is compensated for fall in voltage.

DIRECTIONAL OR REVERSE POWER RELAY- It operates when the applied current and voltage assumes specified phase displacement and no compensation is allowed for fall in voltage.

TYPES OF RELAYS(Contd…)

DIFFERENTIAL RELAY – This relay operates when some specified phase or magnitude difference between two or more electrical quantities occurs.

Switchyard emergencies & Plan of action :

Condition Monitoring

Breakdown Analysis

Annunciations & Alarm schemes:

Circuit breaker condition monitoring annunciations

Alarms related to transmission line & feeder protection

Alarms related to transformer protection

De-Energisation & Isolation of Switchyard Equipment :

When some abnormality observed in a section of the system, the faulty section should be isolated from the main system to safe guard the rest of the system.

When the equipment found defective while in service, isolation of defective equipment or section is necessary to stop further damage to that equipment or surrounding equipment.

THANKYOU

Engineering

Ashwani kumar