A GOVERNMENT OF WEST BENGAL ENTERPRISE

A PROJECT ONHOWRAH 220 KV SUBSTATION

PRESENTED BY:- AVIRUP GHOSH (EE/4TH YEAR/ROLL NO 24)SUBHASHIS GHOSH(EE/4TH YEAR/ROLL NO 27)

SUMAN KUMAR GHOSH(EE/4TH YEAR/ROLL NO 28) ARIJIT MUKHERJEE(EE/4TH YEAR/ROLL NO 49))

Training Duration

• We have completed our vocational training at Howrah 220 kV Sub-station , Danesh Seikh Lane,Howrah from 28.12.2015 to 11.01.2016.The objective of this presentation is to express our experience in a sub-station where we got the practical outline of a system, achieved the overview regarding the practical usage of the power system equipment.

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INTRODUCTION.220KV SUB-STATION.ABOUT WBSETCL.SUBSTATION.IMPORTANT TERMS.OVERVIEW OF HOWRAH 220/132/33 kV SUBSTATION.MAIN ELEMENTS OF HOWRAH SUB-STATION.PANEL SECTION.GROUNDING.SINGLE LINE DIAGRAM.MAINTENANCE OF SUB-STATION.EXPERIENCE OF CORPORAL CULTURE.CONCLUSION.SOURCES.

220kV Substation • It is divided into Three(3) parts:-

A. Panel SectionA. Control Panel SectionB. Relay and Protection Panel Section

B. Switch YardA. 220kV SectionB. 132kV sectionC. 33kV section

C. Battery Room (Extra)

INTRODUCTION

• Now days the electrical power demand is increasing very rapidly. For fulfilling these huge power demands the modern time requires creation of bigger and bigger power generating stations. These power generating stations< may be hydro – electric, thermal or atomic. Depending upon the availability of resources these stations are constructed different places. These places may not be nearer to load centres where the actual consumption of power takes place. So it is necessary to transmit these huge power blocks from generating station to their load centres. Long and high voltage transmission networks are needed for this purpose. Power is generated comparatively in low voltage level. It is economical to transmit power at high voltage level. Distribution of electrical power is done at lower voltage levels as specified by consumers. For maintaining these voltage levels and for providing greater stability a number of transformation and switching stations have to be created in between generating station and consumer ends. These transformation and switching stations are generally known as electrical substations.

ABOUT W.B.S.E.T.C.L.

• West Bengal State Electricity Transmission Company Limited (WBSETCL) was set up in 2007 following the unbundling of the state electricity board of West Bengal. With a share of 4 percent each in the total intrastate transformer capacity, WBSETCL is the eleventh largest of the 23 state transmission utilities in the country. It is responsible for power transmission across the state at the 400 kV, 220 kV, 132 kV and 66 kV Voltage levels. The company also manages the state load dispatch centre, which monitors and controls the grid operations.

Type Public Sector UndertakingIndustry transmissionFounded April 1, 2007 Headquarters Kolkata, West Bengal, IndiaArea served West Bengal, IndiaKey people Sri Gopal Krishna (Power Secretary)Products ElectricityParent WBSEBWebsite www.wbsetcl.in

2008-09 2009-10 Growth (%)

Line length (ckt. km) 11,089.50 11,456.90 3.31

Substations (no.) 93 102 9.68

Transformation capacity (MVA) 13,951.20 16,347.70 17.18

Transmission Losses (%) 3.90 2.74 -

GROWTH STATISTICS

TECHNICAL INFORMATION

TOTAL NO. OF EHV SUB-STATION 103

400 kV SUB-STATION 03

220 kV SUB-STATION 19

132 kV SUB-STATION 70

66 kV SUB-STATION 08

SWITCHING 03

DIST. NO. OF SUB-STATIONS

BANKURA 05

BIRBHUM 03

BURDWAN 10

COOCH BEHAR 01

DAKSHIN DINAJPUR 02

DARJEELING 03

HOOGHLY 11

HOWRAH 04

JALPAIGURI 12

MALDA 03

MURSHIDABAD 07

NAIDA 06

PASCHIM MIDNAPUR 07

PURBA MIDNAPUR 07

PURULIA 03

UTTAR DINAJPUR 02

24 PARGANAS(NORTH) 10

24 PARGANAS(SOUTH) 07

TOTAL 103

SUB-STATIONA substation is a part of an electrical generation, transmission,

and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different voltage levels. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.

Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control.

The word substation comes from the days before the distribution system became a grid. As central generation stations became larger, smaller generating plants were converted to distribution stations, receiving their energy supply from a larger plant instead of using their own generators. The first substations were connected to only one power station, where the generators were housed, and were subsidiaries of that power station.

TYPES OF SUBSTATION

• TYPE ACCORDING TO VOLTAGE CLASS.TRANSMISSION SUB-STATIONDISTRIBUTION SUBSTATIONCOLLECTOR SUB-STATIONSWITCHING SUB-STATION• TYPE ACCORDING TO PURPOSESTEP UP SUBSTATIONPRIMARY GRID SUB-STATIONSECONDARY GRID SUB-STATIONDISTRIBUTION SUBSTATIONMINING SUBSTATIONMOBILE SUB-STATION

• TYPE ACCORDING TO CONSTRUCTIONAL FEATUREESOUTDOOR TYPEINDOOR TYPEUNDERGROUND TYPEPOLE MOUNTING OPEN TYPE

OVERVIEW OF 220/132/25 kV HOWRAH SUBSTATION

Connected Transmission line Line Length(Km)

220 kV Howrah-KTPP double ckt 70

220 kV Howrah-Domjur double ckt via Foundary Park. 48

132 kV Howrah-Liluah 1 & 2 double ckt 12

132 kV Howrah-Liluah 3 & 4 double ckt 15(#3)/24(#4)

132 kV CESC feeder (3 circuits) 24

POWER TRANSFORMERS PRESENTLY IN SERVICE

3*160+1*150 MVA ,220/132/33 KV AUTO TRANSFORMER

• #1

2*20 MVA,132/25 KV TRACTION TRANSFORMER

• #2

BAYS WITH EQUIPMENTS PRESENTLY IN SERVICEBUS SYSTEM BAYS WITH EQUIPMENTS PRESENTLY IN SERVICE220 KV SYSTEM 1.Howrah-KTPP circuit1

2.Howrah-KTPP circuit 23.Howrah-Domjur circuit 1 via Foundary Park4.Howrah-Domjur circuit 2 via Foundary park5. Bus coupler Bay6.220 kV side of 160 MVA Transformer 17.220 kV side of 160 MVA Transformer 28.220 kV side of 150 MVA Transformer 39. 220 kV side of 160 MVA Transformer 4

132 KV SYSTEM 1. Howrah-Liluah circuit 12. Howrah-Liluah circuit 23. Howrah-Liluah circuit 34. Howrah-Liluah circuit 45. Howrah-CESC circuit 16. Howrah-CESC circuit 27. Howrah-CESC circuit 38. Bus Coupler Bay9. 132 kV side of 160 MVA Transformer 110. 132 kV side of 160 MVA Transformer 211. 132 kV side of 150 MVA Transformer 312. 132 kV side of 160 MVA Transformer 413. 132 KV side of 20 MVA 132/25 KV Traction Tr.114. 132 KV side of 20 MVA 132/25 KV Traction Tr.2

33 KV SYSTEM 315 MVA,33/0.4 KV Auxiliary Transformer connected at tertiary of 160 MVA Transformer 2

Important Terms• Tripping – Power goes due to over load . It is for the protection of

components.• Shut down – Power is cut due to maintenance in progress. It is done

manually.• Break down – Power goes due to any fault in the line. When fault is

removed , power is back.• Rosting – Power is cut deliberately on order of higher authority due to

shortage of power.

POWER TRANSFORMERSAlso known as the heart of substations. These are used to reduce the voltages at appropriate levelsINSTRUMENT TRANS FORMARIt is a used in power systems to step downextra high voltage signals and provide a low voltage signal, for measurement or to operate a protective relay

WAVETRAP AND CVT(PLCC SYSTEM)Traps the high frequency signals

ISOLATORSUsed for maintenance of

the circuit in no load condition

CIRCUIT BREAKER used to protect the

eqiupment by opening the circuit for over

current and over voltages

LIGHTINING ARRESTERUsed for protecting the equipment from surge

voltages

MAIN EQUIPMENTS AT HOWRAH SUBSTATION 220KV

OTHER ELEMENTS:E.H.V. TRANSMISSION LINE CONDUCTORS AND CABLESBUS BARSPOWER FACTOR IMPROVEMENT EQUIPMENTBATTERY AND BATTERY CHARGERSSAFETY INSTRUMENTS.

E.H.V. TRANSMISSION LINE TOWERS

• A transmission tower is a tall structure, usually a steel lattice tower, used to support an overhead power line.

• There are four major categories of transmission towers: SUSPENSION,TERMINAL,TENSION and TRANSPORTATION.

• Each tower shall be earthed properly. Earth strips shall be fixed to the tower stubs during concreting of chimney.

Fig-B: Tubular Steel H-Frame Tower Fig-c: Lattice Tower With Double Circuit Fig-A: Lattice Tower With Single Circuit

CONDUCTOR USED IN E.H.V.TRANSMISSION LINE

• Generally in E.H.V. transmission line MOOSE and PANTHER conductors are used.

• Normally MOOSE are used for 220 kv & above.• PANTHER are used for 132 kv. Fig: Panther Conductor Fig: Moose Conductor

WIRES AND UNDERGROUND CABLES

• WIRES: Aluminum-conductor steel-reinforced(ACSR) cables are primarily used for medium and high voltage lines and may also be used for overhead services.

Fig: Zebra Conductor Fig: Dog Conductor

WIRES AND UNDERGROUND CABLES• UNDERGROUND CABLES: The design and construction of underground transmission

lines differ from overhead lines because of two significant technical challenges that need to be overcome. These are:

1. Providing sufficient insulation so that cables can be within inches of grounded material.

2. Dissipating the heat produced during the operation of the electrical cables.

INSULATORS• An electrical insulator is a material whose internal electric charges do not flow freely and therefore

make it very hard to conduct an electric current under the influence of an electric field.• PROPERTIES: 1. High mechanical strength in order to withstand conductor load, wind load etc.2. High electrical resistance of insulator material in order to avoid leakage current to earth.• TYPES:

1. PIN Type 2.SUSPENSION Type

INSULATORS• TYPES:

3. STRAIN Type 4.SHACKLE Insulator

5. POST Insulator 6.GUY Insulator

LIGHTNING ARRESTER• A lightning arrester is a device used on electrical power systems and

telecommunications 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.

WAVE TRAP & CVT • WAVE TRAP: Power-line communication(PLC) carries data on a conductor that is also used

simultaneously for AC electric power transmission or electric power distribution to consumers. Wave trap communicates between two sub-station by power lines.

WAVE TRAP & CVT • CVT: The Ferro resonant transformer, Ferro resonant regulator or constant-voltage

transformer is a type of saturating transformer used as a voltage regulator.

INSTRUMENT TRANSFORMER• The lines in sub-station operated at high voltage and carry current of thousands amperes. The measuring instruments and

protecting devices are designed for low voltage(110V) and current(5A).There are two types of instrument transformer-

1. CURRENT TRANSFORMER: Current transformers(CT) are a series connected type of instrument transformer. They are designed to present negligible load to the supply being measured and have an accurate current ratio and phase relationship to enable accurate secondary connected metering.

SPECIFICATION OF 220 KV CURRENT TRANSFORMER

Sl. No. SPECIFICATION VALUES

1 Feeder Name Domjur-II

2 Rated kV 245

3 Ph R

4 Manufacturer Alstom

5 Mfg. year 2004

6 Ratio Amps 1000-800/1-1-1-1-1

7 Connected Ratio 800

8 Burden VA 30-40-40-40-40

9 Class 05-PS-PS-PS-PS

10 Commissioning Date 03-May-07

INSTRUMENT TRANSFORMERFig: Current Transformer

INSTRUMENT TRANSFORMER2. VOLTAGE TRANSFORMER: Voltage transformers(VT)(also called potential transformers(PT)) are a parallel

connected type of instrument transformer, used for metering and protection in high-voltage circuits or phasor phase shift isolation.

SPECIFICATION OF 220 KV POTENTIAL TRANSFORMERSL.NO. SPECIFICATION VALUES

1 Feeder Name 220 kV PT-a

2 Kv class 245

3 Phase R

4 Manufacturer Rade Koncar

5 Serial no 776089/75

6 Mfg year NA

7 Ratio 220000:110-110

8 Burden VA 300

9 Class A/B

INSTRUMENT TRANSFORMER

Fig: Voltage Transformer

POWER TRANSFORMER• A transformer is an electrical device that transfers energy between two or more

circuits through electromagnetic induction.ACCESSORIES OF TRANSFORMER:CORE: The core has stepped cross-section.WINDING: The conducting material used for the windings depends upon the

application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn.

BUSHING: Bushing is output condenser type or porcelain type depending upon the voltage class.

OIL TANK: The tank is welded mild steel plate construction, shot blasted an inside and outside to remove scale before painting. The tank is coated inside with two coat of yellow oil proof enamel. On the outside it is applied with anticorrosive primer paint and final coat of synthetic enamel to shade as per customer’s specification.

POWER TRANSFORMERPROTECTION OF TRANSFORMER: The principle relays and systems used for transformer

protection are:Buchholz devices: Providing protection against all kinds of incipient faults.Earth-fault relays: Providing protection against earth-faults only.Overcurrent relays: Providing protection mainly against phase-to-phase faults and

overloading.Differential relays: Providing protection against both earth and phase faults.

POWER TRANSFORMER

SPECIFICATIONS OF 150 MVA TRAFO-III INSTALLED AT HOWRAH 220 KV SUBSTATION:TRANSFORMERS PARTICULARS IMPEDENCE VOLTS AND BIL(KV)

Make: CGL Impedance volts(HV-IV):11.46% at N tapSerial no.: 24822 Impedance volts(HV-LV):45.92% at N tapManufacturing year: 1988 Impedance volts(IV-LV):29.81% at N tapCommissioning date:03-Dec-90 BIL(kV)-HV:900(peak)/395(r.m.s.)Phase: 3 BIL(kV)-IV:550(peak)/230(r.m.s.)Frequency: 50Hz BIL(kV)-LV:170(peak)/70(r.m.s.) Vector Group: Yna0d11 BIL(kV)-Neutral:38(r.m.s.) Voltage ratio(kV): 220/132/33Rated capacity(kVA): 150000

POWER TRANSFORMERSPECIFICATIONS OF 150 MVA TRAFO-III INSTALLED AT HOWRAH 220 KV SUB-STATION:

RATED CURRENTS(AMPS) ONAN ONAF OFAF

MVA AMPS MVA AMPS MVA AMPSHV 75.00 197.00 112.50 NA 150.00 393.60IV 75.00 328.00 112.50 NA 150.00 656.10LV 22.50 394.00 33.75 NA 45.00 787.30

COOLING

Cooling type ONAN/ONAF/OFAFTemp rise of oil(0c) 40Temp rise of winding(0c) 55Oil(main tank)(liters) 45100Oil(OLTC tank)(liters) 510

WEIGHTWeight(core WDG)(k.g.) 60000

Weight(accessories)(k.g.) NA

Weight(oil)(k.g.) 39460Weight(total)(k.g.) 132800

BUS BAR

BUS BAR

• A bus bar in electrical power distribution refers to thick strips of copper or aluminum that conduct electricity within a switchboard, distribution board, substation, or other electrical apparatus.

BUS-BAR ARRANGEMENT IN A SUB-STATION:• Bus-bars are important components in a sub-station. There are several bus-bar arrangements that

can be used in a sub-station. They are:i. Single bus-bar system: As the name suggests, it consists of a single bus-bar and all the incoming

and outgoing lines are connected to it.ii. Single bus-bar system with sectionalisation: In this arrangement, the single bus-bar is divided into

sections and load is equally distributed on all the sections.iii. Duplicate bus-bar system: This system consists of two bus-bars, a “main” bus-bar and a “spare”

bus-bar.

CIRCUIT BREAKER A circuit breaker is equipment, which can

open or close a circuit under normal as well as

fault condition. These circuit breaker breaks

for a fault which can damage other instrument

in the station. It is so designed that it can be

operated manually (or by remote control)

under normal conditions and automatically

under fault condition. Whenever a fault occurs

trip coil gets energized, the moving contacts

are pulled by some mechanism & therefore the

circuit is opened or circuit breaks.

Fixed contact

Moving contact

ARC

Fixed contact

Moving contact

ARCARC IS QUENCHED BY MEDIUM

Two contacts called electrode remains closed under normal operating conditions. When fault occurs on any part of the system, the trip coil of the circuit breaker get energized and contacts are separated.

Operating Principle

The Electric ArcDuring the separation of contacts, due to large fault current and high current density at the contact region the surrounding medium ionizes and thus a conducting medium is formed. This is called the ARC.

Factors responsible for arc:-Potential difference between the

contacts.Ionized particles between the

contacts.

Arc quenching is achieved by:Greater dielectric strength than restriking

voltage.Faster rate of heat removal than rate of heat

generation.

Arc extinction methods are: By lengthening the gap.Cooling the arc.Inserting medium of high dielectric strength.

PRINCIPLES OF ARC EXTINCTION

TYPES OF CIRCUIT BREAKERS

Oil circuit breaker 

Air-blast circuit breaker

Sulphar hexafluoride circuit breaker (SF6)Vacuum circuit breakers

OIL CIRCUIT BREAKERIt is designed for 11kv-765kv.These are of two types

• BOCB (Bulk oil Circuit Breaker)• MOCB (Minimum oil Circuit Breaker)

The contacts are immersed in oil bath.

Oil provides cooling by hydrogen created by arc.

It acts as a good dielectric medium and quenches the arc.

Advantages of oil:Oil has good dielectric strength. Low cost.Oil is easily available.It has wide range of breaking capability.Disadvantages of oil:Slower operation , takes about 20 cycles for arc quenching.

It is highly inflammable , so high risk of fire.

High maintenance cost.

AIR BLAST CIRCUIT BREAKERSThis operates using high velocity blast of air

which quenches the arc.It consists of blast valve , blast tube &

contacts.Blast valve contains air at high pressure.Blast tube carries the air at high pressure &

opens the moving contact attached to spring.There is no carbonization of surface as in VCB.Air should be kept clean & dry to operate it

properly.

Advantages:High speed operation as compared to OCB.Ability to withstand frequent switching.Facility for high speed reclosure.Less maintenance as compared to OCB.Disadvantages:Little moisture content prolongs arcing time.Pressure should be checked frequently for

frequent operation.Risk of fire hazards due to over voltages.It can’t be used for high voltage operation

due to prolonged arc quenching.

SF6 CIRCUIT BREAKERS It contains an arc interruption chamber containing

SF6 gas. In closed position the contacts remain surrounded

by SF6 gas at a pressure of 2.8 kg/cm2 .During opening high pressure SF6 gas at 14

kg/cm2 from its reservoir flows towards the chamber by valve mechanism.

SF6 rapidly absorbs the free electrons in the arc path to form immobile negative ions to build up high dielectric strength.

It also cools the arc and extinguishes it.After operation the valve is closed by the action

of a set of springs.Absorbent materials are used to absorb the

byproducts and moisture.

Advantages: Very short arcing period due to superior arc quenching

property of SF6 . Can interrupt much larger currents as compared to other

breakers. No risk of fire. Low maintenance, light foundation. No over voltage problem. There are no carbon deposits.

SF6 breakers are costly due to high cost of SF6. SF6 gas has to be reconditioned after every operation of the

breaker, additional equipment is required for this purpose.

Disadvantages:

VACCUM CIRCUIT BREAKERIt is designed for medium voltage

range (3.3-33kv).This consists of vacuum of pressure

(1*10-6) inside arc extinction chamber.The arc burns in metal vapor when

the contacts are disconnected.At high voltage , it’s rate of dielectric

strength recovery is very high.Due to vacuum arc extinction is very

fast.The contacts loose metals gradually due to formation of metal vapors.

Advantages:Free from arc and fire hazards.Low cost for maintenance & simpler mechanism.Low arcing time & high contact life.Silent and less vibrational operation.Due to vacuum contacts remain free from

corrosion.No byproducts formed.Disadvantages:High initial cost due to creation of vacuum.Surface of contacts are depleted due to metal

vapors.

Circuit Breaker Comparison

SF6 CIRCUIT BREAKER

• Gas is used as an arc quenching medium.

• It is an electronegative gas.• It has a tendency to absorb

free electrons.

VACUUM CIRCUIT BREAKER

• Vacuum is used as an arc quenching medium.

• It has very fast rate of recovery of dielectric strength.

• The arc is extinguished quickly.

SPECIFICATION OF 220 KV CIRCUIT BREAKER INSTALLED AT HOWRAH 220 KV SUB-STATIONSL.NO. SPECIFICATION VALUES

1 FEEDER NAME 220 KV BUS COUPLER

2 RATED VOLTAGE(KV) 245

3 RATED CURRENT(AMPS) 2000

4 MAKE TELK

5 SF6/MOCB SF6

6 TYPE OFPI-200

7 SERIAL NO 860037-3

8 OPERATING AIR PRESSURE 16KG/CM^2

9 OPERATING GAS PRESSURE 6KG/CM^2

10 MFG YEAR 1994

11 COMMISSIONING DATE 30.06.1998

ISOLATORIsolator

 Used to ensure that an electrical circuit is completely de-energised for service or maintenance. Such switches are often found in electrical distribution  and industrial applications, where machinery must have its source of driving power removed for adjustment or repair. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers, transformers, and transmission lines, for maintenance. The disconnector is usually not intended for normal control of the circuit, but only for safety isolation. Disconnector can be operated either manually or automatically (motorized disconnector)

STEPS OF OPERATION OF ISOLATOR SEQUENCE OF STEPS FOR ATTENDING

MAINTENANCE:

1. Open CB on no load or full load

2. Open the isolator on no load

3. Close the earth switch

SEQUENCE OF STEPS FOR KEPT IN SERVICE

4. Open the earth switch

5. Close the isolator

6. Close the CB

Methods of Reactive Power Compensation

• Shunt compensation• Series compensation• Synchronous condensers• Static VAR compensators• Static compensators

Series compensation

• When a device is connected in series with the transmission line it is called a series compensator. A series compensator can be connected anywhere in the line.

• There are two modes of operation – capacitive mode of operation and inductive mode of operation.

• A simplified model of a transmission system with series compensation is shown in Figure .The voltage magnitudes of the two buses are assumed equal as V, and the phase angle between them is δ.

Shunt compensation

• The device that is connected in parallel with the transmission line is called the shunt compensator. A shunt compensator is always connected in the middle of the transmission line. It can be provided by either a current source, voltage source or a capacitor.

• An ideal shunt compensator provides the reactive power to the system.

• Shunt-connected reactors are used to reduce the line over-voltages by consuming the reactive power, while shunt-connected capacitors are used to maintain the voltage levels by compensating the reactive power to transmission line.

Synchronous Condensor• A device whose main function is the

improvement of power factor of the electrical system is known as the synchronous condensor. It is installed at the receiving end of the line .

• When a synchronous condensor is introduced it supplies the kVAR to the system , and hence the current is reduced .

• Therefore the losses are reduced and provides a better efficiency . Hence more power can be delivered to the load and improves the power factor of the system.

Battery Room & Charger

•It is responsible of supplying all the relay panels which are situated in control room•Typically room containing the battery bank is dark in color to avoid the evaporation of solution inside the battery

Panel Section• It is a room which contains all types of panels. • Typically a control panel consists of

Metering Equipments. Controlling Equipments. Protective Relaying.

• Control Cables are laid between Switchyard equipment and these panels.

Importance of control panel

• Control and Relay panel is most important equipment of the substation as it work as shield guard for all substation equipments and electrical network. Moreover, these panels are useful to control the flow of electricity as per the Voltage class and detect the faults in transmission lines.

There is no ‘fault free’ system. It is neither practical nor economical to build a ‘fault free’ system. Electrical system shall tolerate certain degree of faults. Usually faults are caused by breakdown of insulation due to various reasons: system aging, lightning, etc.

Why A System Needs Protection?

PROTECTIVE RELAY

CurrentVoltageInsulationTemperature

Pick up levels Time

Visual indication

Warning alarm

Remove power

output

input

setting

A protection relay is a smart device that receive inputs, compares them to set points, and provide outputs .Inputs can be current ,voltage ,resistance or temperature. Outputs can include visual feedback in the form of indicator lights.A diagram is shown below.

Relay

Functional Characteristics of a protective relay

1.Reliability

2.Selectivity

3.Speed

4.Sensitivity

OPERATING PRINCIPLE There are really only two fundamentally different operating principles, 1. Electromagnetic attraction 2. Electromagnetic induction Electromagnetic attraction relays operate by virtue of a plunger being drawn into a solenoid. Electromagnetic induction relays use the principle of

the induction motor whereby torque is developed by induction in a rotor.

TYPES OF RELAY Types of protection relays are mainly based on their characteristics ,logic, on actuating parameter & operation mechanism.

Based on operation of mechanism1. Electromagnetic relay2. Static relay3. Mechanical relay

Based on actuating parameter1. Current relay2. voltage relay3. Frequency relay4. Power relay

Based on characteristics

1. Inverse time relay with definite minimum2. Instantaneous relays3. IDMT with Instrument4. Stepped characteristics5. Programmed switches6. Voltage restraint over electric current relay7. Definite time relay.

Based on application

1. Primary relay2. Back up relay

Based on logic 1.Differential 2. Unbalance 3. Neutral displacement 4. Direction 5. Restricted earth fault 6. Over fluxing 7. Distance scheme 8. Bus bar protection 9. Reverse power relay 10. Loss of excitation 11. Negative phase sequence relay

Importance of relay

•By adequate protection the damage can be eliminated or minimized.•Inadequate protection can lead to a major fault that would have been avoided.

•If the faulty part is disconnected quickly the damage caused by fault is minimum.

•The protective relaying helps in improving service continuity and its importance to self evident.

SUB STATION GROUNDING

Sub-station grounding is needed -------• To provide discharge path for lightning over voltages coming via rod-

gaps, surge arresters, and shielding wires etc. .• To ensure safety of the operating staff by limiting voltage gradient at

ground level in the substation• To provide low resistance path to the earthing switch earthed

terminals, so as to discharge the trapped charge (Due to charging currents even the line is dead still charge remains which causes dangerous shocks) to earth prior to maintenance and repairs.

MORE ABOUT GROUNDINGTERMS NEED TO KNOW--- EARTH RESISTENCE.STEP POTENTIAL AND TOUCH POTENTIAL.TYPES OF GROUNDING—UN EARTHED SYSTEM.SOLID GROUNDING.RESISTENCE GROUNDING.REACTANCE GROUNDING.RESONANT GROUNDING.DIFFERENT GROUNDING EQUIPMENTS---Earthing Electrodes

Earthing MatRisersOverhead shielding wire (Earthed)

MAINTENANCE OF A SUB-STATION

Maintenance is classified in two categories as follows:• The breakdown or corrective maintenance activities are undertaken

after failure of an equipment. Such maintenance results in outage of circuit and supply. In general, it consists of locating the trouble, repair and re commissioning.

• The preventive maintenance is undertaken to ensure smooth and efficient working of a system, equipment. Preventive maintenance is undertaken as per schedule before breakdown of a system or machine takes place.

ACTIVITIES RELATED TO MAINTENANCE INSPECTION.SERVICING.EXAMINATION.OVERHAUL.REQUIRMENTS OF THE ABOVE VARY WITH ENVIRONMENTAL ASPECTS.OPERATING DUTY.SWITCHING DUTY SEVERITY.

WHAT IS SINGLE LINE DIAGRAM?A single line diagram is diagrammatic representation of power

system in which the components are represented by their symbols and interconnection between them are shown by a straight line(even though the system is three phase system).The ratings and the impedances of the components are also marked on the single line diagram.

So One-line diagram or a single line diagram is a diagram that uses single lines and graphic symbols to indicate the path and components of an electrical circuit.

PURPOSE AND EXAMPLEOne-line diagrams are used when information about a circuit is required but

detail of the actual wire connections and operation of the circuit are not.The purpose of the single line diagram is to supply in concise form of the

significant information about the system.

OTHER ASPECTS OF INDUSTRIAL TRAININGLET US REVISE WHAT ARE THE PURPOSES OF AN INDUSTRIAL TRAINING????THEN WHAT MORE???

WE OFTEN FORGET ABOUT THE SOFT SKILL IT OFFERS. CORPORATE COMMUNICATION. CORPORAL WORK ENVIRONMENT. CORPORATE CULTURE. OVERVIEW OF PROFESSIONAL RESPONSIBILITIES. CORPORATE MANARISM AND OTHER SOFT SKILL.

CONCLUSION

• An Engineer need to have not just theoretical but practical as well as and so every student is supposed to undergo a practical training session. where one may have impaired the knowledge about transmission ,distribution . One must have never thought that so many things are required for just switching on a television or a refrigerator or say an electric trimmer. The three wing of electrical system viz. Generation, transmission and distribution are connected to each other and that too very perfectly. Lots of labour, capital and infrastructure is involved in the system just to have a single phase,220V,50Hz power supply at our houses.

BIBLIOGRAPHY

GUPTA,J.B.,A COURSE IN POWER SYSTEM.KOTHARI,D.P.AND NAGRATH,I.J. POWER SYSTEM ENGINEERING.ROY,SANJIB.DIVISIONAL ENGINEER.MUKHERJEE,SOURAV.ASSISTANT ENGINEER.www.wbsetcl.comwww.wikipedia.com