220KV SWITCHYARD AT

UNCHAHAR

PRESENTED BY:

NITISH KUMAR GUPTA

ET-2011

OPERATION-GROUP C

Substations

• HVAC : 220, 400, 765 KV• HVDC: +/- 140, 200, 400, 500, 800 KV

• Air Insulated Substation• Gas Insulted Substation

• Indoor • outdoor

COMPONENTS OF 220KV SWITCHYARD

• Bus-Bar.• Circuit Breakers (C.B.).• Current Transformers

(C.T.).• Potential Transformers

(P.T.).• Capacitive Voltage

Transformers (C.V.T. ).• Lightning Arrester (L.A.).• Isolators.• Earthing Switch.• Line traps

Layout & Schematic Diagrams

C.T.P.T.

L.A.

C.B.

BUSBAR

ISOLATOR

EARTHING SWITCH

CVTCVT

Busbar arrangements

• Single busbar• Double busbar• double busbar with transfer bus• Mesh busbar• Double Breaker• 1-1/2 breaker

Single busbar

lines

coupler

Double Busbar

Double Main and Transfer Busbar (DMT)

Transfer Bus

Bus#1

Bus#2

1 1/2 Breaker scheme

SYSTEM ARRANGEMENT AT UNCHAHAR

BUS-3

BUS-4

Transfer BUS

G-3

GT-3

UAT-3BUAT-3A

GCB

LINE ISOLATOR

BUS SECTION BREAKER

BUS-1

BUS-2

BUS ISOLATORS

220 KV SWITCHYARD SCHEME ( GENERATOR )

15.75 KV

6.6 KV Unit Buses

220 KVEarth Switchs

13-52-A,B,C

89-13-3

250MVA, 15.75/237KV

16MVA, 15.75/6.9KV

89-13-289-13-1 89-13-4

BUS-3

BUS-4Transfer BUS

ST-3

LINE ISOLATOR

BUS SECTION BREAKER

BUS-1

BUS-2

BUS ISOLATORS

220 KV SWITCHYARD SCHEME ( STATION TRANSFORMER )

6.6 KV Station Buses

220 KV

14-52-A,B,C

89-14-3

89-14-189-14-2

SE-2SE-1

40 MVA, 22/6.9kV

89-14-4

BUS-3

BUS-4Transfer BUS

LINE ISOLATOR

BUS SECTION BREAKER

BUS-1

BUS-2

BUS ISOLATORS

220 KV SWITCHYARD SCHEME

( TRANSFER BUS COUPLER )

220 KV

TBC Breaker

89-17-3

89-17-289-17-4

89-17-1

17-52-A,B,C

BUS-3

BUS-4Transfer BUS

BUS SECTION BREAKER

BUS-1

BUS-2

220 KV SWITCHYARD SCHEME

( BUS COUPLER )

B/C BKR

23-52-A,B,C

BUS-3

BUS-4Transfer BUS

LINE ISOLATOR

BUS SECTION BREAKER

BUS-1

BUS-2

BUS ISOLATORS

220 KV SWITCHYARD SCHEME ( OUTGOING FEEDERS- KANPUR 1 )

Line Breaker

OUTGOING FEEDERS

19-52-A,B,C

89-19-1

89-19-3

89-19-289-19-4

POWER EVACUATION SCHEME AT UNCHAHAR

KANPU

R-4

KANPU

R-1

RB-3

FP-1

KANPU

R-3

KANPU

R-2

FP-2

RB-1

U#2 U#1U#3

MAIN BUS 3 AND 4 MAIN BUS 1 AND 2

RB-2

SECTIONALIZER ST-1

ST-2

ST-3

ST-4

U#5 U#4

Feeder Arrangement

S.No Feeder Type No of Feeders/Bays

1 Generator 05

2 Station Transformer 04

3 Outgoing Transmission Line 09

4 Bus-Section Breaker 01

5 Bus-Coupler Breaker 02

6 Transfer Bus-Coupler 02

EQUIPMENT DESCRIPTION

CIRCUIT BREAKERS

1. ALL THE THREE STAGES HAVE SINGLE PRESSURE, PUFFER TYPE SF6 CIRCUIT BREAKERS

2. OPERATING MECHANISMS OF BREAKER FOR THE THREE STAGES ARE DIFFERENT:

PNEUMATIC HYDRAULIC SPRING

DESCRIPTION OF VARIOUS C.Bs 1. PNEUMATICALLY OPERATED SF-6 C.B. BREAKER MAKE- CGL SF6 GAS P- 6KSC RATED VOLTAGE- 245kV RATED CURRENT- 3150 Amp S.C.C- 40kA (3 SEC.) S.C. BREAKING CURRENT- 40kA LIGHTING IMPULSE WITHSTAND V- 1050kV (p to p)

AIR PARAMETERS: NORMAL- 15KSC COMPRESSOR START- 14.5 KSC COMPRESSOR STOP- 15.5 KSC AIR PRESSURE LOW ALARM- 13.2 KSC AIR PRESSURE LOW LOCKOUT- 12.0 KSCSF6 PARAMETERS: NORMAL- 6.0 KSC ALARM- 5.5 KSC LOCKOUT- 5.0KSC

DESCRIPTION OF VARIOUS C.Bs

2. HYDRAULICALLY OPERATED SF-6 C.B. BREAKER MAKE- BHEL SF6 GAS P- 6.5KSC RATED VOLTAGE- 245kV RATED CURRENT- 2800 Amp S.C.C- 40kA (3 SEC.) LIGHTING IMPULSE WITHSTAND V- 1050kV (p to p)

NORMAL OIL PRESSURE- 313-325 bar ALARM- 273 bar LOCKOUT- 253 bar

SF6 PARAMETERS: NORMAL- 6.5 KSC ALARM- 5.7 KSC LOCKOUT- 5.5KSC

FILTER

PUMP

NRV

P.SW

P.SW

CYLINDER

MAIN VALVEY1(CLOSE)Y2/Y3(OPEN)

OIL N2

OIL TANK

SAFETYVALVE

PRESSURE RELIEFVALVE

Pr GAUGE

ACCUMULATOR

ELECTRO HYDRAULIC MECHANISMFOR 220 KV SF-6 BKR

DESCRIPTION OF VARIOUS C.Bs

3. SPRING OPERATED SF-6 C.B. BREAKER MAKE- ALSTOM RATED VOLTAGE- 245kV RATED CURRENT- 2500 Amp S.C.C- 40kA (3 SEC.) LIGHTING IMPULSE WITHSTAND V- 1050kV (p to p)

Isolators/Disconnectors

• USED FOR ISOLATING THE CIRCUIT PHYSICALLY• OPERATE AT NO LOAD• INTERLOCKED WITH BREAKERS AND EARTHSWITCHES• SHOULD WITHSTAND EXTREME WIND PRESSURES• MOTOR DRIVEN AND HAND DRIVEN• LOCAL AS WELL AS REMOTE OPERATION POSSIBLE• ISOLATES SECTIONS FOR MAINTENANCE

FEATURES OF EARTH SWITCHES

• USED TO GROUND SECTIONS REQUIRED FOR MAINTENANCE

• GROUND TRAPPED CHARGES & INDUCTION VOLTAGES

• INTERLOCKED WITH BREAKERS AND ISOLATORS• CAN BE OPERATED FROM LOCAL ONLY• MOTOR DRIVEN AS WELL AS HAND DRIVEN• SAFETY DEVICE

Current Transformer

• Function– To isolate Instrument from High voltage– Reduce High current into low current

• Dead Tank• Live Tank• Optical CT

CURRENT TRANSFORMER

• ITS VA RATING=30VA• SECONDARY CURRENT= 1Amp• IT HAS 5 SECONDARY CORES• CORE-1 BUS BAR MAIN ZONE• CORE-2 BUS BAR CHECK ZONE• CORE-3 METERING CORE• CORE-4 DIFFERENTIAL PROTECTION• CORE-5 DIRECTIONAL OR O/C PROTECTION

Voltage Transformer

• Function– Isolation from high voltage– Reduce high voltage into low voltage

• Electromagnetic• Capacitor voltage transformer

CAPACITIVE VOLTAGE TRANSFORMER

• SECONDARY VOLTAGES(110 VOLTS AC) FOR VOLTMETERS AND ENERGY METERS

• VOLTAGES FOR PROTECTIVE RELAYS• VOLTAGES FOR SYNCHRONIZING • DISTURBANCE RECORDERS AND EVENT LOGS• OVERFLUX RELAYS• PLCC

CVT Equivalent Circuit

Z 2

U 1

C1

C2 U 2

Lightning arrester

• Device connected between conductor and ground which protects power equipments from abnormal high voltages.

Sources of overvoltage

EXTERNAL:-– LIGHTENING – GEOMAGNETIC STORM.

INTERNAL – SWITCHING

• LINE/CAPACITOR SWITCHING.• INDUCTIVE CURRENT BREAKING

RELAYS

…Development of Relay TechnologyRelay Electromechanica

lStatic Numerical

Measuring Element

Magnets, coil, Induction disc, etc

Diodes, Transistor,Comparators, ICs, etc

Microprocessor based, DSPs etc

Measuring Mode

Electrical Quantities converted to mechanical forces, torque

Detectors, Comparison with Reference value in Analog Comparator

A/D Converters, Numerical Algorithms etc

Timer Mechanical clock works, dashpot

Static timers Counters

Indication Flags LEDs LEDs, LCD

FUNCTIONS PERFORMED BY NUMERICAL RELAY

PROTECTION

COMMUNICATION

CONTROL

CONDITIONMONITORING

FUNCTIONS PERFORMED BY NUMERICAL RELAY

AUTORECLOSING

• 80% OF FAULTS ARE OF TRANSIENT NATURE, SO JUST BY INTERRUPTION OF SUPPLY WE CAN REMOVE THEM

• AT EHV LEVELS ONLY ONE RECLOSURE IS ALLOWED TO AVOID THE POSSIBILITIES OF UNSTABLE LOAD SWING(AT DISTRIBUTION LEVELS 3 RECLOSURES ARE GIVEN BEFORE LOCKOUT, AS THERE THE MAIN COCERN IS CONTINUITY OF SUPPLY)

AUTO-RECLOSE RELAY

• THESE ARE LOCKOUT TYPE ELECTROMECHANICAL RELYS

• RECLOSE TIME- 20 Sec• ONCE LOCKOUT, WE HAVE TO RESET IT MANUALLY• AUTO-RECLOSE SELECTION SWITCH:1. SINGLE PHASE(NORMAL SELECTION)2. THREE PHASE

Power Line Carrier Communication

• Uses same Power wire for communication• Uses High frequency for communication• Voice signal and Protection signal are

modulated on carrier frequency

C=1/2ΠFC

30KHZ TO 500KHZ

IMPEDENCE 75 OHMS

WAVE TRAP2ΠFL

L

PLCC

POWER FREQ -50 KHZ

STATION BUS

LINE

BASIC ARRANGEMENT OF WAVE TRAP AND COUPLINGCAPACITOR

>500KHZ NOISE PICKUP<30KHZ-HARMONICLIGHTENING,CORONA

WAVE TRAP

1.RATED INDUCTANCE( 0.5/ 1.0mH)

2.RATED CURRENT

3.BAND WIDTH

4.COUPLING (PHASE TO PHASE)

SWITCHYARD AUXILIARY SYSTEMS

• AC SUPPLY FOR CONTROL ROOM• A RELIABLE 415V AC SUPPLY ( LT SWGR)• 220 V & 48 V DC SUPPLY( BATTERY & BATTERYCHARGER)• POWER & CONTROL CABLE• LIGHTING ( Yard lighting & indoor lighting of control room)• AIR CONDITIONING

AT UNCHAHAR WE HAVE 2* 1 MVA , 6.6KV/433V TRANSFORMERS WHICH PROVIDE AUX. AC SUPPLY FOR SWITCHYARD

PROCEDURES AND SYSTEM

TAKING A CIRCUIT OUT OF SERVICE

TAKING ISOLATION ON A FEEDER

1. OBTAIN SHUTDOWN APPROVAL CODE FROM NRLDC/CPCC/CLDS BASED ON WRITTEN MESSAGE FROM UCR END

2. INTIMATE THIS CODE TO REMOTE END FOR OPENING OF LINE FROM REMOTE END

3. OPEN LINE BKR AND ISOLATOR FROM UCR END4. AFTER OPENING OF LINE ISOLATOR & BREAKER FROM REMOTE END

&UCR END, INTIMATE FOR CLOSING OF LINE EARTH SWITCH AT REMOTE END.

5. NOW CLOSE EARTH SWITCH AT UCR END & INTIMATE IT TO REMOTE END6. ISSUE PTW TO EMD

NORMALIZING A FEEDER 1. ENSURE PTW CANCELLATION AND CLEARANCE FROM EMD2. INTIMATE NRLDC/CPCC/CLDS FOR ISSUE OF LINE NORMALIZATION AND

CHARGING CODE TO BOTH ENDS. CONFIRM IT FROM REMOTE END ALSO3. GIVE MESSAGE TO REMOTE END FOR OPENING OF EARTH SWITCH AND

NORMALIZATION OF LINE AND BUS ISOLATOR AT THEIR END4. AFTER GETTING CONFIRMED MESSAGE FROM REMOTE END, OPEN EARTH

SWITCH AND NORMALIZE LINE AND BUS ISOLATOR AT UCR END’5. INTIMATE IT TO REMOTE END BY WRITTEN MESSAGE AND REQUEST FOR

CHARGING OF LINE FROM REMOTE END UNDER INFORMATION TO UCR END6. AFTER GETTING CLEARANCE FOR CHARGING FROM REMOTE END,

SYNCHRONIZE THE LINE(WITH THE HELP OF SYNCHRONIZING TROLLEY)FROM UCR END

7. OBSERVE LINE V & I OF ALL 3 PHASE; IN CASE OF ABNORMALITY INFORM TO EMD

VARIOUS ALARMS

ALARMS ON CONTROL PANEL- THEY TELL US THE FINAL ACTION OR STATE

FLAGS ON RELAY PANEL- THEY HELP US TO FIND OUT THE CAUSE

CONTROL PANEL

RELAY PANEL

ALARMS RELATED TO GT PROTECTION

• BKR TC1/TC2 FAULTY• LBB PROTECTION OPERATED• BREAKER AUTO TRIP• BREAKER GENERAL LOCKOUT• BREAKER POLE DISCREPENCY• PANEL DC-1 FAIL• PANEL DC-2 FAIL

ALARMS RELATED TO ST PROTECTION

• BKR TC1/TC2 FAULTY• LBB PROTECTION OPERATED• BKR AUTO TRIP• BKR GENERAL L/O• BKR POLE DISCREPENCY• TRAFO O/C & E/F PROTECTION OPERATED• TRAFO BUCHHOLZ RELAY OPERATED• TRAFO OIL TEMP/WDG TEMP TRIP• EARTH TRAFO TRIP• TRAFO PRV1/PRV2 OPERATED• TRAFO DIFFERENTIAL OR REF PROTECTION OPERATED• PANEL DC1 FAIL• PANEL DC2 FAIL• OVER FLUXING PROTECTION

ALARMS RELATED TO FEEDER PROTECTION

• BKR TC1/TC2 FAULTY• LBB PROTECTION OPERATED• BKR GENERAL L/O• BKR AUTO TRIP• FAULT LOCATOR DC FAIL• DISTANCE RELAY ACQUISITION UNIT FAILURE• AUTO RECLOSE L/O• PLCC CHANNEL 1/2 FAIL• PANEL DC FAIL• POWER SWING DETECTED• OVERVOLTAGE OR BROKEN CONDUCTOR• MAIN 1/2 CARRIER RECEIVED• MAIN 1/2 DIRECT TRIP

PROTECTION PHILOSOPHIES

• PROTECTION OF BUS BAR • PROTECTION OF FEEDER• PROTECTION OF STATION TRANSFORMER

BUS BAR PROTECTION

PRINCIPLE: CIRCULATING CURRENT DIFFERENTIAL PRINCIPLE

CURRENT DISTRIBUTION – EXTERNAL FAULT

CURRENT DISTRIBUTION FOR INTERNAL FAULTS

PRACTICAL VARIANTS OF BBP

• HIGH IMPEDANCE TYPE

• LOW IMPEDANCE BIAS TYPE

HIGH IMPEDANCE TYPE

Relay Branch made High Impedance to limit differential current due to unequal CT saturation on external fault.

Reqires exclusive CT core of identical ratio and rating.

Simple in design and execution.

LOW IMPEDANCE (BIASED) TYPE

• Through current Bias increases differential pick-up on external fault to ensure stability.

• Tolerant to CT mismatch and can use shared core.• Comparatively more complex in design and execution.• Practical schemes provide CT saturation detectors to enhance stability.

FEEDER PROTECTION

VARIOUS PROTECTIONS APPLIED TO FEEDERSARE:1. DISTANCE PROTECTION2. OVERCURRENT PROTECTION3. CARRIER CURRENT PROTECTION

OTHER PROTECTIONS INCLUDE:UNDERVOLTAGE PROTECTION

CLASSIFICATION

1. Protection against Electrical FaultsUnit Protection (against Internal Faults) Differential Protection. REF Protection.

Non-Unit Protection (against un cleared external faults) IDMT O/C, E/F Relays. Definite Time O/C, E/F Relays.

2.Protection against Abnormal Conditions Over Load protection Over Fluxing Protection

3. Protective Devices (Non-electrical) Buchholz (Main Tank / OLTC) Oil / Winding Temperature Indicators / Relays Pressure Release Valve Oil Level Gauges / Indicators

TRANSFORMER PROTECTION

EFFECTS OF VARIOUS SWITCHYARD EMERGENCIES ON GENRATOR

1.FEEDER FAULT BUT AUTORECLOSE SUCCESSFUL

2.UNSUCCESSFUL AUTORECLOSE- TRIPPING OF FEEDER AND LOCKOUT

3.MULTIPLE FEEDER TRIPPING4.BUS BAR FAULT

CASE 1

• ROTOR WILL SPEED UP A BIT WHICH WILL CAUSE IN AN INCREASE IN THE POWER ANGLE

• STABLE POWER SWINGS WHICH WILL SLOWLY DAMP OUT

• NO PERSISTENT CHANGE IN THE GENERATOR O/P

CASE 2

• FOR A SINGLE FEEDER TRIP THERE WILL BE SUDDEN LOSS OF HUGE LOAD ON THAT BUS WHICH WILL CREATE TRANSIENT IN SYSTEM

• POWER SWINGS WILL OCCUR• BECAUSE OF INTERCONNECTION OF ALL THE

BUSES WE CAN STILL MAINTAIN ALL THE UNITS BUT AT A SLIGHTLY REDUCED LEVEL

CASE 3

• DEPENDING UPON THE MAGNITUDE OF LOSS OF LOAD WE MAY HAVE TO SUBSTANTIALLY REDUCE THE LOAD ON ALLL THE UNITS

• IN WORST CASES WE HAVE TO SHUT DOWN UNITS TO REDUCE INFEED ON EACH BUS

CASE 4

• INSTANTANEOUS TRIPPING OF : 1. BUS COUPLER OF CONCERNED BUS 2. BUS SECTIONALIZER OF CONCERNED BUS 3. A VERY SEVERE TRANSIENT 4. ALL THE GENERATORS CONNECTED TO THAT

BUS 5. TRIPPING OF ALL FEEDERS AND STs

CONNECTED TO THAT BUS

• IN THIS CASE WE MAY HAVE TO REDUCE LOAD ON REST OF THE UNITS ALSO BY SMALL AMOUNTS BECAUSE WE REMOVED THE INTERCONNECTION OF BUSES

EFFECTS OF FAULTS – CTD.

CROSSING THE ELECTRICAL REGIME AND ENETRING INTO MECHANICAL ASPECTS:

• HUGE TORSIONAL STRESSES ARE DEVELOPED IN GENERATOR AND TURBINE SHAFTS DUE ELECTRICAL DISTURBANCES

• THESE MAY RESULT IN TOTAL FATIGUE

CONDITION MONITORING OF SWITCHYARD EQUIPS.

EARTHING AND SAFETY OF PERSONAL

1. THE OBJECTIVE OF EARHING IS TO MAINTAIN A LOW POTENTIAL ON ANY OBJECT

2. IN A SUBSTATION AREA EARTHING LIMITS THE POTENTIAL GRADIENT WITHIN AND IMMEDIATELY OUTSIDE THE AREA TO A VALUE, SAFE FOR THE WORKING PERSONNEL.

REQUIREMENT OF A GOOD EARTHING • THE EARTH RESISTANCE FOR THE SWITCHYARD AREA

SHOULD BE LOWER THAN A CERTAIN LIMITING VALUE“RA” IN ORDER TO ENSURE THAT A SAFE POTENTIALGRADIENT IS MAINTAINED IN THE SWITCHYARD AREA AND PROTECTIVE RELAY EQUIPMENT OPERATE SATISFACTORILY. FOR MAJOR SWITCHYARDS AND SUBSTATIONS IN INDIA, THIS LIMITING VALUE OF EARTH RESISTANCE (RA) IS TAKEN TO BE LESS THAN 0.5 OHM.

• THE GROUNDING CONDUCTOR MATERIAL SHOULD BE CAPABLE OF CARRYING THE MAXIMUM EARTH FAULT CURRENT WITHOUT-OVERHEATING AND MECHANICAL DAMAGE. THE MAXIMUM FAULT LEVEL IN THE 220 KV SYSTEM HAS BEEN ESTIMATED TO BE 30 KA AND THIS VALUE OF FAULT CURRENT IS USED IN THE DESIGN OF EARTH MAT FOR THE 220 KVSUBSTATION.

THANK YOU

LBB PROTECTION (50Z)

• Provides local isolation when breaker gets stuck on fault.

• Ensures comparatively faster clearance than remote backup.

TRANSFORMER PROTECTION

Buchholz Relay

Petcock

From transformer

Deflector plate

Trip bucket

To oilconservator

Mercury switch

Alarm bucket

Transformer

To oil conservator

Bucholtz Protection Application

Accumulation of gas

Oil Leakage

Severe Winding Faults

Colour of gas indicates the type of fault

White or Yellow : Insulation burnt

Grey : Dissociated oil

Accumulation of gas

Gas can be extracted for detailed analysis

Accumulation of gas

Severe winding fault

Severe winding fault

Severe winding fault

Pressure Relief Valve The pressure relief valve (PRV ) is designed as

a safety device to be used on power transformer and similar oil filled electrical equipments . When pressure in tank rises beyond predetermined safe limit , the PRV operates and performs following functions

1.Reduces the pressure in the 2.Secondly, along with above mentioned

function ,operates a switch which can be used to initiate precautionary electrical system

Overfluxing

Transient Overfluxing - Tripping of differential element Prolonged Overfluxing - Damage to transformers Here value of k=1.25

Effects

m2

I e

m

V = k

Overfluxing - Condition Differential element should be

blocked for transient overfluxing-+

25% OVERVOLTAGE CONDITION

43% 5TH HARMONIC CONTENT

Overfluxing waveform contains very high 5th Harmonic content

V = Kf

• Trip and alarm outputs for clearing prolonged overfluxing

• Alarm : Definite time characteristic to initiate corrective action

• Trip : IT or DT characteristic to clear overfluxing condition

Overfluxing - Protection

DISTANCE PROTECTION

What is distance protection?

RELAY

IntendedREACH point

Z

Transient Overreach

• Fault current generally contains dc offset in addition to ac power frequency component

• Ratio of dc to ac component of current depends on instant in the cycle at which fault occurred

• Rate of decay of dc offset depends on system X/R

Typical load characteristic impedance

+R

Operate

area

No Operate area

+XL

+ = LOOKING INTO LINE normally considered forward

Load Trajectory

Rea

ch

Load Swings

Typical Protection SchemesLong Lines

• Phase comparison• Directional Comparison Blocking (DCB)• Permissive Underreach Transfer Trip (PUTT)

Distance Schemes

Pilot Aided Schemes

No Communication between Distance

Relays

Communication between Distance

relays

Non-Pilot Aided Schemes

(Step Distance)

Bus

Line

Bus

Zone 1

Zone 2

Zone 2

Zone 1

To protect end ofline

& Local Trip Zone 2

Rx

OR Zone 1

PUTT Scheme