CHAPTER 21
DATA ON ELECTRICAL SYSTEM
1. Introduction
2. Data on Electrical Circuit Study 3. Data on Protection Scheme
4. Data on Electrical System Equipment 5. Transmission Line Data
6. Transmission Line Conductor Data 7. Data on Electrical Clearances 8. Electrical Earthing System Data
9. Data on Distribution System ( Up to 33 KV System ) 10. Data on Sub- Station
11. Electrical Standards
12. Data on Power Telecommunication
13. Meaning s of Indications for Different Distance Protection Relays 14. Diagnostic System/ Maintenance Scheduled Of Electrical Equipment
1. Introduction:-
Data on the Electrical System are the most useful tool for the Electrical engineers to know the limit of their working arena. According to the limitation of Data, proper planning, estimation and confirmation regarding the equipments can be achieved. Basically the practice Engineer are very cautious regarding the value of threshold on the Electrical Parameters, upon the field works on the Equipments on which they work to obtain the efficiency of the assigned project. Many a times they get confused to land upon a decisive conclusion; due to the non-availability of ready reckon electrical data. This chapter has covered all the possible zones of electrical field topics with some reference data in concise manner. The reference tips on the maintenance schedule, testing methods, installation practice and commissioning patterns can help the Electrical Engineers to acquaint themselves and develop a healthy environment by refining their practice towards the field works.
2. DATA ON ELECTRICAL CIRCUIT STUDY 2.1 STANDARD CONNECTING WIRE
2.1 DEVICE IDENTIFICATION CODE
CODE NO. FUCTION /DEFINITION 1 2 3 4 9 12 13 14 20 21 22 Master Element
Time Delay Starting or Closing Relay Checking or Inter locking Relay Master Contactor
Reversing Device Over Speed Device
Synchronous- Speed Device Under Speed Device Electric Operated Device Distance Protection Relay Equalizer Circuit Breaker
LETTERS PURPOSE LETTERS PURPOSE
A B C D E F H J K L CT Secondary Circuit special Bus Bar Protection Protection AC Circuit (CT ) Metering Circuit PT Secondary Fan Control Circuit LT AC Supply DC Main Circuit Control (Trip, Close etc Alarm, Indication, Annunciation Circuit M N S U X Motor Control Circuit Transformer Tap Changer Control Circuit Marking of Sec. CT Polarity Used for spare wires
Used for spare wires
CODE NO. FUCTION /DEFINITION 23 25 26 27 29 30 34 37 40 43 47 49 50/50N 51/51N 52 52a/52b 53 54 55 57 59 60 61 63 64 65 67/67N 68 69 72 74 76 78 79 80 81 83 85 86 87 88 89 90 91 92 94 95 96
Temp. Control Device Synchronism Check Device Apparatus Thermal Device Under voltage Relay Isolator Contactors Annunciation Relays
Motor Operated Sequence Switch. Under Power Relay
Field Failure Relay
Manual Transfer Selector Switch Phase Sequence Voltage Relay
Thermal Relays (Machine/ Transformer) Instant O/C Relay/ Instant E/F Relay AC Time Delay O/C Relay/ E/F Relay AC Circuit Breaker
CB Aux. Switch – N/O, CB Aux. Switch – N/C Exciter of DC Generator Relay
High Speed DC Circuit Breaker Power Factor Relay
Short Circuiting Or Ground Device Over Voltage Relay
Voltage Relay
Current balance Relay
Liquid- Gas pressure level Relay (Buch.) REF Protective Relay
Governor
AC Directional O/C Relay / E/F Relay Blocking Relay
Permissive Control Device DC Circuit Breaker Alarm Relay Dc O/C Relay
Phase Angle Measure/ OUT of Step Protn. AC Reclosing Relay
DC Fail Supervision Relay Frequency Relay
Automatic Sel. Control / Transfer Relay Carrier or Pilot wire Receive Relay Master Relay (Locking –out Relay) Differential Protective Relay Aux. Motor or Motor Generator Line Switch (Isolator)
Regulating Device Voltage Directional Relay Power Dir. Relay
Tripping or Trip free Relay Trip Circuit Supervision Relay Tripping Relay
2.2 SYMBOLS USED SL. No Symbols Meanings 1. Over Current 2 V Over Voltage 3 V Under Voltage 4 Z Distance Relay
5 X Balanced or Diff. Current
6 Over Frequency 7 Under Frequency 8 T Over Temp. 9 Balanced Phase 10 X PW Pilot Wire 11 Dirr. O/C 12 Z Dir. Distance 13 CC Carrier Pilot 14 I
O/c Ground with Instant Element
15 B X Bus Current Diff. 16 B X
2.4. SYMBOL AND DESIGNATIONS BASED ON THE (INTERNATIONAL ELECTRO TECHNICAL COMMISSION STANDARD) IEC 617 - SERIES AND IEEE C37.2 – 1991 2.4.1 GENERAL BLOCKS
Symbols Meanings Symbols Meanings
Protection relay
Coil with flag indication (ON)
Protection relay with enable input
Coil with no flag
Protection relay with blocking input
3phase O/C relay with settable delay
Coil with flag indication (OFF)
Under impedance relay
Direction E/F current relay with one input (current) and after (voltage), and one for block
Relay with mechanical contracts (Auto reset
2.4.1 PARAMETERS, SYMBOLS AND FUNCTIONS
Symbols Meanings Symbols Meanings
I Reverse current I Drop out delay
Id Differential current Inverse time lag characteristics
Inf Current of nth Harmonic Step I1 , Ip Positive sequence current LO Lockout
I2 , In - Xe sequence current TCS Trip circuit supervision
I0 , Ip Zero sequence current O I Transition from OFF to ON position (e.g.: Auto reclose
Irsd Residual current I O Tripping
* * EN * EN 3I> Z < I EN
Id Current to frame X/Y Translation of signal IN-N Current between neutral
and two poly phase system
> Operation above a set value
IN Current on neutral < Operation below a set value
Iub Unbalance current >
<
Operation outside set limits (e.g. voltage regulation)
Thermal effect by current
Make contract (Self reset) (Normally open)
U Voltage Break contact (Self reset)
(Normally close)
P Active power Change over contract (Break
before make)
P Power at phase angle Time delay (drop off)
Q Reactive power Time delay (pick up)
Temperature Normally open contract (Hand
reset)
Fault, Flash over. Normally close contact (Hand
reset)
Thermal effect Positional contact (Bold marked
position in considered)
Delay Push button (Normally open)
P.T, V.T
Push button (Normally close )
Isolator Fuse
Breaker C.T.
CVT Wave trap
2.5 CODE OF PRACTICE BY M/S ABB LTD. 2.5.1 TERMINAL BLOCKS
EXTERNAL CIRCUIT INTERNAL CIRCUIT
TB PURPOSE TB PURPOSE
X01 CT Circuit X11 CT Circuit
X02 PT Circuit X12 PT Circuit
X03 DC Supply X13 DC Supply
X04 Control Circuit X14 Control Circuit
X05 AC Supply X15 AC Supply
X07 Annunciation,
AlarmCircuit
X17 Annunciation,
AlarmCircuit
2.5.2 EQUIPMENT/ DEVICE TERMINAL IDENTIFICATION FOR M/S ABB LTD 2.5.2.1 Modular identification: - It is designated by co-ordinate system of U and C/TE U Height of module
C/TE Horizontal distance between mounting holes (width of module) Note: Modular's upper left corner U and C/TE co-ordinate is taken.
01 17 25 37 1
2 3
101 325 137 2.5.2.2 Modular Terminal Identification
E.g.101: 26 101, 137, 325 - are modular number 137: 321 26, 321, 222 - Terminal number
325: 222
3. DATA ON PROTECTION SCHEME 3.1 CLASSIFICATIONS
• Apparatus Protection
(Generator, Motor, Transformer, breaker etc.. ) • Bus Protection • Line Protection 3.2 GENERATOR PROTECTION 3.2.1 Class A Protection INITIATION OF RELAYS INTERMEDIATE
AUX. RELAY ACTION OF CIRCUIT BREAKER
Trip Gen. CB
87G Trip Field. CB
87GT Trip Turbine
87UAT Trip UAT BkrA
64G1 Trip UAT BkrB
64G2 Initiate 6.6 KV CB
59G Initiate LBB
99GT Arm- Reheater Protection
64REF Block Closing of Gen. CB
51UAT Block Field CB
50UAT 64R II STAGE Rotor Over Voltage Excite Transf. O/C Buch. PRDS GT1,UAT1 Class A Trip Relay 86G 32 G &
3.2.2 Class B Protection 3. 2.3 Class C Protection INITIATION OF RELAYS INTERMEDIATE AUX. RELAY ACTION OF CIRCUIT BREAKER
81U/F TRIP GEN. CB
B/B PROTECTION 21GB IST. STAGE H.P/L.P BYPASS FAST OPN.
46G IST STAGE Class C Trip Relay 86 GB SING. GT INITIATE LBB 98G (POLE SLIP) INITIATION OF RELAYS INTERMEDIATE AUX. RELAY ACTION OF CIRCUIT BREAKER 46G 40G 21GB (II STAGE ) 81 GCB (OPEN) TRIP TURBINE
STATER CONDN. HIGH WATER FLOW LOW
Class B Trip Relay 86T
TRIP UAT CB
AUTO & MANUAL PULSE FAIL THYRISTOR COOLING
FAN SUPPLY FAIL FCB CLOSE
Initiate 6.6 KV CB
TRANS. OIL TEMP. & WINDING
ARM.REHEATER PROTECTION
3.2.4 Proposed Protection Equipments for different types of Generators Generator Size Protection I 0 – 4 MVA II 4 –15 MVA III 15 – 50 MVA IV 50 – 200 MVA V Large Turbo Alternator Rotor Overload X Rotor E/F X X X X X Inter turn Fault X 4 X 4 X 4 X Differential Generator X X X X Diff. Block Transformer X X X X Under frequency X 3 X 3 X 3 4 Over Voltage X X X X X Stator E/F X X X X X Loss of Excitation X X X X
Pole- Slip (Out of Step) X X Reverse Power X 1 X 5 X 5 X 5 X Under Impendence X 2 X X Unbalance (I2 Current) X 7 X 7 X X Over Current (Definite Time) X 6 X 6 Stator Over Load X Over Current / Under Voltage X 6 X 6 Dead Machine X X X Breaker Failure X X X
Note: - 1- Only necessary for Steam and Diesel Drives
2. Only necessary for Thyristor excitation from Generator terminals 3. Only necessary for Pump operation.
4. Only necessary for when several Bars of the same phase in the same slot 5. Not necessary for PELTON turbines
6. O/ C should not be used with self supported static excitation system 7. When unbalance load is expected
3.2.4 THERMAL PLANT UNIT PROTECTIONS SL.
NO
BOILER PROTECTION TURBINE PROTECTION
GENERATOR PROTECTION 1 Loss of unit critical DC
Power
Protection System Power Failure
Generator Differential Protection
2 Less than fire ball
Loss of AC at any elevation in service
Low Condenser vacuum (2 Channels)
Overall Differential protection
3 Very low drum water level for more than 5 Secs
Thrust bearing Oil
pressure high (2 Channels)
UAT’ s diff. Protection 4 Very high drum water level
for more than 10 Secs
High Shaft vibrations Over fluxing protection 5 Failure of both FD fans Electrical over speed Loss of Excitation
protection 6 Failure of both ID fans Main steam Temp. Very
low
Negative phase sequence protection
7 Unit air flow as low as 30 % High exhaust steam Temp. Backup Impendence protection
8 Furnace pressure very low Over frequency Protection Over voltage protection 9 High furnace pressure Digital Electro hydraulic
control power failure
Under Frequency Protection 10 Loss of Fuel (3 out of 4
nozzle valves open)
Failure of CWPS Over Load protection 11 Unit flame failure trip All valves mainly main
stop valve, reheat stop valves, interrupt control valves closure
Pole stop Protection
12 Loss of Re-heater protection Under Frequency Protection
Generator Under voltage associated with loss of excitation protection
13 Reverse power protection 95 % back charging stator
E/F protection
14 Mechanical Over speed
protection
95 % stator E/F protection 15 Low auto stop Oil pressure 100 % stator E/F protection
16 Reheat protection Excitation field protection
17 Dead machine relaying
under independent GCB closure
18 Protection of VT fuse
19
Loss of 220 V DC
ATRS emergency turbine trip
Protection for GT restricted E/F Protection
3.3 MOTOR PROTECTION 1 O/L Protection 2 S.C. Protections 3 E/F Protections 4 Start Protections 5 Prolonged starts
6 Stalling protections During starting
During running 7 Loss of load
8 Under voltage protection
3.4 TRANSFORMER PROTECTION 3.4.1 Requirement of relays BACK UP GAS OPERA TED RELAY TEM P PRO TEC TION CAPACIT Y OF TRANSFO RMER 3 O/ C 2 O/ C E/F B U C H O S R P R V O T I W TI DIF F REL AY RE F RE LA Y NEUT. DISPL RELA Y NEUT. O/C RELA Y OVE R FLU X UP TO 5 MVA - R R R O - R R O O - O - 5 to 12.5 MVA R - R R R O R R R O O R O ABOVE 12.5 MVA R Dir. - R Dir. R R R R R R R O O R AUTO TRANS. R Dir. Inst. - R Dir. Inst. R R R R R R R - O R
3.4.2 CIRCUIT FOR DIFF. PROTECTION (TRANSFORMER ) Transformer Winding Connection Sec. CT Diff. Connection Transformer Winding Connection Sec. CT Diff. Connection Remark Dy1 Y1d Yd11 Y d1 D1y Dy11 1. D1 Connection corresponds ( I R - I B ) Dy11 Y11d Yd1 Y d11 D11y Dy1 2. D11 Connection corresponds ( I R - Iy)
PRIMARY SIDE P2 TERMINAL OF CT CONVENTIONALLY TOWARDS TRANSFORMER
3.4.3 BUCHHOLTZ RELAY 3.4.3.1 Data:
1) Works on principal of BUOYANCY of liquid. 2) Position on pipe bent tank and conservator
3) Angle of inclination of pipe with horizontal 5 to 10 4) Length of straight run pipe section
(I) Transformer to relay = 5D (min) (II) Relay to conservator = 3D ( min )
D : Dia of pipe
5) Vertical position of relay from tank = 8 cm ( min ) 6) Gas volume for Alarm operation
Trans. Size Pipe dia
Setting range Normal setting Upto 1 MVA 2.5 cm 100 - 120cc 110cc 1 to 10 MVA 5 cm 185 - 250cc 220cc 10MVA and
above
7.5 cm 220 - 280cc 250cc
8) Diagnosis of Troubles from color of gas collected
Colour Identification Colour Identification Colorless Air Grey Gas of overheated oil
due to burn of iron White
/Milky
Gas of decomposed paper and cloth insulation Yellow Gas of
decomposed wood insulation
Black Gas of decomposed oil due to elect. Arc.
3.4.4 PRV (PRESSURE RELEASE VALVE)
3.4.4.1 Data: 1 required / Universal for nitrogen cushioned transformer and optional for conservator type transformer
3.4.4.2 Data: 2 Alarm -0.32 kg/cm²/sec, Trip - 0.6 kg/cm²/sec
3.4.4.3 Data: 3 Work on the principle of activation bellow due to pressure 3.4.5 OTI (OIL TEMP. INDICATOR)
3.4.5.1 DATA: 1 Work on the principle of volumetric change in bellow and corresponding conversion on scale due to temperature.
3.4.5.2 DATA: 2 Temp. Rise above ambient ( TABLE) Type of winding Top oil find temp
rise on F.L condition Winding temp rise on F.L. condition OA, OW 50ºC 55ºC OA / FA 50ºC 55ºC OA / FA / FOA FOA FOW 45ºC 50ºC
3.4.6 WTI (WINDING TEMP. INDICATOR)
3.4.6 .1 DATA: 1 Bellow (Bourdon tube) and shunt network, being connected to WCT (Winding Ct), simulates the temp. Gradient, (proportionate with load current) and provides reading on the scale.
3.4.6.2 DATA: 2 Max. Heater coil current 2 Amps
3.4.6.4 DATA :-4 TEMPERATURE Vrs CURRENT SIGNAL CHARACTRISTICS FOR RTD
( REMOTE THERMAL; DEVICE ) BS 1904 & DIN IEC 751
OUT PUT SIGNAL 0-5mA
OUT PUT SIGNAL 0-20mA
OUT PUT SIGNAL 4-20mA TEMP
IN O C
RESISTANCE
L0 Nom. Hi L0 Nom. Hi L0 Nom. Hi
0 100.00 - 0 0.050 - 0 0.200 3.800 4.000 4.200 10 103.90 0.283 0.333 0.383 1.333 1.333 1.533 4.867 5.067 5.267 20 107.79 0.617 0.667 0.717 2.467 2.667 2.867 5.933 6.133 6.333 30 111.67 0.950 1.000 1.050 3.800 4.000 4.200 7.000 7.200 7.400 40 115.54 1.283 1.333 1.383 5.333 5.333 5.533 8.067 8.267 8.467 50 119.40 1.617 1.667 1.717 6.467 6.667 6.867 9.133 9.333 9.533 60 123.24 1.950 2.000 2.050 7.800 8.000 8.200 10.200 10.400 10.600 70 127.07 2.283 2.333 2.383 9.333 9.333 9.533 11.267 11.467 11.667 80 130.89 2.617 2.667 2.717 10.467 10.667 10.867 12.333 12.533 12.333 90 134.70 2.950 3.000 3.050 11.800 12.000 12.200 13.400 13.600 13.800 100 138.50 3.283 3.333 3.383 13.333 13.333 13.533 14.467 14.667 14.867 110 142.29 3.617 3.667 3.717 14.467 14.667 14.867 15.573 15.733 15.933 120 146.06 3.950 4.000 4.050 15.800 16.000 16.200 16.600 16.800 17.000 130 149.82 4.283 4.333 4.383 17.333 17.333 17.533 17.667 17.867 18.067 140 153.58 4.617 4.667 4.717 18.467 18.667 18.867 18.733 18.933 19.133 150 157.31 4.950 5.000 5.050 19.800 20.000 20.200 19.800 20.000 20.200 3.5. BREAKER PROTECTION
1 Pole discrepancy Relay (PDR) 2. Local Breaker Back up relay (LBB) 3. 5.1 TIME CHART OF PDR: - Breaker Close Pole
Operation Discrepancy
Normal Breaker Close Time t PDR Operation Tripping Margin Time Contact
T
t Mismatch allowable closing time between poles
T It should be less than timing of unbalances current relay and zone 2 time of D.P. relay.
3. 5.2. TIME CHART OF LBB RELAY: -
(Fault
Occurrence )
Normal Clearing Time
(1 ) ( 2 ) ( 3 ) Margin
Set time for Time Meas. Unit ( 4 ) ( 5 ) Margin Breaker
Fail Relay Starts
Total Clearing time of LBB Relay
Maxim. Fault clearing time before system Instability
(1) Protection Relay operation Time (Ex. DP Relay) (2) Breaker Interruption Time
(3) Resetting Time Current Measuring Unit (4) Trip Relay Time
(5) Back up Breaker Interruption Time 3.6. BUS PROTECTION
1 High impedance circulating current protection. 2 Biased Differential circulating current protection. 3.7. LINE PROTECTION
1 Main Protection (Distance Protection) 2 B/U Protection (O/C, E/F Protn.)
3.7.1 MAIN PROTECTION (DISTANCE PROTECTION) 3.7.1.1 STANDARD 3 ZONE PROTECTION
1st Method
Zone 1 80% of protected line.
* Zone 2 100% of protected line + 50% of shorted adjacent * * Zone 3 100% of protected line +100% of longest adjacent line.
* Maximum zone 2 reach should be within the minimum effective Zone 1 reach of adjacent line.
2nd. Method
For available of the following data zone selection standard should be as follows a3 = 0.85 ( a + k b2) a2 = 0.85 ( a + k b1) a1 = 0.85 a b 1 a b 2 A B C NOTE Z1 :- a1 = 0.85 a ( Zone 1 ), Z2 :- a2 = 0.85 ( a + k b1 ) Z3 :- A3 = 0.85 ( a + k b2) = Zone 3 k = ( IA + IB ) / IA ,
Where IA = Service current on Station A IB = Service current on Station B 3. 7.1.2 TIME STANDARD
Accepted fault clearance timing of
EHV line.
Selection of DP Relay Time
System Time Zone Time
400 kV 80 ms Zone 1 Instant Relay operation time ( 30 to 40 mS ) 220 kV 100 ms Zone 2 0.2 to 0.5 S Zone 3 0.4 to 1 S 132 kV 150 ms Reverse Zone 1 to 2 S
3.7.1.3 MINIMUM DE- ENERGISATION TIME
( FOR 3 PHASE DISCONNECTION ON TRANSMISSIOM LINE) Line KV Minimum
De- Energisation
Time in Sec.
Line KV Minimum De- Energisation
Time in Sec.
66 0.1 220 0.28
110 0.15 275 0.3
3.7.1.4 FAULT, VOLTAGE AND CURRENT INVOLVEMENT IN TRANSMISSION LINE
Phase - Earth Fault Phase - Phase Fault Voltage Current Fault Voltage Current Fault
Va Ia + 3KIo a - g Vab Ia - Ib a-b Vb Ib + 3KIo b - g Vbc Ib - Ic b-c Vc Ic + 3KIo c - g Vca Ic - Ia c-a Where K = Zero seq. compensation - factor
= (Z0 – Z1) /3Z1
Zo - Zero Seq. impendance Z1 - +ve - Seq. impendance Io = Zero Seq. current 3. 7.1.5 ARC - RESISTANCE FORMULA (A.R. VAN C. WARRING TON)
1st Method: -
Ra = 28707 (L + ut) / I 1.4
L = Length of arc (Length of Insulator String) in mtr. U = Wind velocity in Km/hr
I = Actual fault current in Amp. 2nd Method: -
Ra = (440 x Arc length in feet) Fault current
3. 7.1.6 DATA ON ARC ON THE TRANSMISSION LINE Arc Resistance of Line Sec. Voltage due to Arc
for 220 KV Line, Arc Distance 1.12mtr and PTR 2000 Line Voltage in KV Length In Mtr Ra (Arc Resistance) Ohm Fault Current in KAmp. Sec. Voltage in mV 33 1.22 2.5 40 221 132 3.66 8.6 20 292 220 6.7 12.8 10 386 400 8.3 18 5 509 2 735 1 970
3. 7.1.7 TYPE OF D.P. RELAY I Impedance
ii Reactance
iii Mho or Admittance iv Ohm v Offset mho vi Modified impedance vii Elliptical viii Quadrilateral ix parallelogram
3. 7.1.8 D.P RELAY SETTING CALCULATION 3.7.1.8.1 Data – Assumed line parameter data
Line Voltage R ohm/ ph/km X ohm/ ph/km Yc µ mho/ph/km 132kv Panther 0.151 0.401 1.43 220kv Zebra 0.078 0.402 1.44 400kv Twin Moose 0.031 0.327 1.73
3.7.1.8.2 Formulae for parameter calculation 1 #R1 = l /a ohm/ph/km # R1 -+ve Sequence Resistance
(Usually given in conductor data)
2 X1 = 2 f x 2 x 10 –4 ln (Dm / Ds) ohm /ph/km X1 = +ve seq. reactance
Dm = Mutual Geometric Mean Distance = (Dmab x Dmbc x Dmca) 1/ 3
Dmab = Mutual GMD between 'A' and 'B' conductor of the Line Dmbc = conductor between 'B' and 'C'
Dmca = Between 'C' and 'A' conductors Ds = Self GMD
Note: - For Double circuit loop reactance = 2 X 1
3 Ro = Zero sequence resistance
4. Xo = Zero seq. reactance Ohm/ph/km
= (0. 01397 f /1.609) x log 10 De / (GMR conductor x GMD 2sep) 1 / 3 ohm/ph/km
De = Equivalent depth return in mtr = 658 x ( / f)
= Earth Resistivity in ohm-mtr
GMR conductor = Self radius = 0.7788 r
GMD sep = (Dab x Dbcx Dca) 1/ 3
Dab= Distance Between A & B Conductor , Dbc = Between B & C, Dca=Between C & A 5.Rom = Zero seq mutual resistance
Rom = 0.00477f ohm/ph/km 1.609
6. Xom = Zero seq. mutual reactance
= ( 0. 01397 f /1.609 ) x log 10 (De / GMD eq ) ohm /ph/km
(GMD)eq = ninth root of products of all nine possible distance between two circuit 3.7.1.8.3 Minimum Load Impedance (Z L )
Z L =(U² / MVA)
Where U = Line to Line voltage,
MVA = Maximum permitted load = (Umin. / 3 I max.)
3.7.1.8.4 Conversion to secondary value Z Sec = Z pri x C.T.R
P.T.R Base = P.U x KV² impedance value 100
3.7.1.8.5 Zero seq. compensation factor (KN)
i. KN = (Zo – Z1) / 3Z1, When mutual zero seq. impedance is not considered. = (Xo – X1 ) / 3X1 ,
ii. K 0 angle = Tan-¹ (Xo - X1) / (Ro - R1) --Tan-¹ (X1) / R1
iii. KNP = (Xo +Xom - X1 ) / 3X1 , When parallel system in normal operation
iv. KNG = (Xo² - X²om - XoX1 ) / 3XoX1 For parallel system is out of service and grounded at both ends.
3.7.1.9 POSSIBLE LENGTH OF LINE AND OPTIMUM POWER TO BE TRANSMITTED.
Possible optimum power transmission Possible length in KM Line voltage KV Line loading KW - KM Length Minimum Line Max. 11 24x10³ - - 33 200x10³ - - 66 600x10³ 40 120 110 11x10 6 50 140 132 20x10 6 50 160 166 35x10 6 80 180 230 90x10 6 100 300
3.7.1.10 SUITABILITY OF RELAY PERFORMANCE 3.7.1.10.1 1st Method: -
Minimum voltage at relay: - S.I.R: - System Impedance Ratio
= Source Impedance Relay setting impedance
C.I.R: -Characteristics Impedance Ratio
= Maximum value of system impedance ratio = E - V
V
E - P.T. Secondary voltage V - Minimum voltage at relay
Zs =(KV² ) / (MVA) Fault/source = Source impedance
IF = KV for 3Ø fault current 3 (Zs +ZL)
ZL = Line Impedance Vrelay = E/ (1+Zs / ZL)
3.7.1.10.2 2nd Method: - ii. Ph - Ph fault
Vrelay = ( 3 ZL x I F) / PTR OR VT Ratio
ii. Ph - Earth fault
Vrelay = (IF x Zre) / VT ratio
Zre - Earth loop impedance = ZL1 (1 + (K-1)/3) Where K = ZLo / ZL1,
ZLo = Zero sequence impedance, ZL1 = +re sequence impedance
3.7.1.11 SELECTION OF POWER SWING BLOCK 1 (Block Z1 = OFF), (Block Z2 Z3 = ON) 2 During PS ( Z / t) Slow
3.7.2 O/C AND E/F PROTECTION 1 Non-Dir B/U Protection , 2 Directional B/U Protection 3.7.2.1 TYPE
(a) Definite Time relay
(b) Inverse Definite Minimum Time Lag Relay (IDMTL) (i) Normal Inverse (NI)
(ii) Very Inverse (VI) (iii) Extremely Inverse (EI) (iv) Long time Inverse (LTI)
3. 7.2.2 OPERATING CHARACTERISTICS (IDMTL RELAY) (IEC 255-4 BS 142, 3.2) t = K x Tm Where t =Operating time in Second
( I / Is) C -- 1 I = Fault current in Amp.
Is = start current = 1. 1 IB in Amp Tm = Time Multiplier Value of 'K' and 'C' Type K C N I 0.14 0.02 V I 13.5 1.0 E I 80 2.0 L T I 120 1.0
3. 7.2.3 ERRORS OF IDMTL RELAY (AS PER BS 142 LIMITS)
Any PS and 1.0 time setting
100% Plug setting and 1.0 time setting Operating current (Multiple of plug setting) % Sec % Sec 2 ± 24.15 ± 2.42 ± 16.65 ± 1.67 5 ± 15.98 ± 0.69 ± 8.48 ± 0.36 10 ± 15.08 ± 0.45 ± 7.58 ± 0.23 20 ± 15.00 ± 0.33 ± 7.5 ± 0.17
3. 7.2.4 O/C + E/F RELAY HIGH SET SETTING 3. 7.2.4.1 Max. 3Ø Short circuit current
(i) (At beginning of line) I max = U / 3 Zs, (ii) (AT end) I max = U / 3 (Zs+ZL)
(iii) (Source impedance) = Zs = KV² / MV A
3. 7.2.4.2 Minimum setting of relay Imin = 1.3 Imax
Safety factor 1.2 Irelay = 1.2 Imin
3. 7.2.4.3 O/C Highest
Relay setting = (Irelay) / CTR
3. 7.2.4.4 E/F High set =O/C High set 3
3. 7.2.5 DIRECTIONAL B/U RELAY (O/C)
Relationship between MTA (Maximum Torque Angle) and relay connection of O/C relay Connection Aph Bph Cph Relay connecti on angle MTA Current coil Voltage coil Current coil Voltage coil Current coil Voltage coil 30º 0º Ia Vac Ib Vba Ic Vcb 60º Type 1
0º Iab Vac Ibc Vba Ica Vcb
60º Type 2
0º Ia - Vc Ib - Va Ic - Vb
90º 30º Lead Ia Vbc Ib Vca Ic Vab
90º 45º Lead Ia Vbc Ib Vca Ic Vab
3.7.2.6 DIRECTIONAL B/U RELAY (E/F)
Connection Relay
characteristic angle
Current coil Voltage coil 12.5º (lag) 14º (lag) 45º (lag) 60º (lag) Residual Current I0 = IA + IB + IC Residual Voltage = Open Delta Secondary
Voltage
3.7.2.7 CONTACTS, TERMINALS FOR OTHER RELAYS OF GEC ALSTOM MAKE
CONTACTS Sl No Model Standard Alar m Trip Current Terminal Voltage Termin al Aux. DC 1 MVAA23 Two unit/Case 23-25 9-11 15-17 1-3 13-14 27-28 220-250V 2 MCAG34 THREE/Case 2-4 1-3 23-24, 25-26,27-28 # # 24-26-28 SHOTRTE D 3 MCAG14 Single unit/Case 2-4 1-3 27-28
4 MCGG22 Single unit/Case 6-7 8-10 1-2 15-16 27-28 13-14 5 MCGG62 THREE/Case 36-37 33-35 29-30 41-42 21-22 23-24, 25-26 # 13- 14 # 22-24-26 SHORTED 6 MBCH12 Single Unit/Case 9-11 1-3 2-4 23-25-27 7 MVAP22 23-25-27 8 MCVG62 25-23-21 Short 37&42, 41&46, 38&45 9 MWTU11 27-28 25-23-21 10 MCND04 7-9 18-20 13-14 11 MYTU04 7-9 6-8 13-14 12 MVTU12 4-16 27-28 13 MCSU 4-6 1-3 27-28 13-14
3. 7.2.8 CONTACTS, TERMINALS FOR B/U RELAYS OF DIFF. MANUFACTURERS Trip
Make Type Standard Alar
m Nor mal Inst ant Current Terminal Volt age Aux. DC Single unit/Case 1,2 3,4 11,1 2 9,10 - 5,6 Multi unit/Case 3O/C 1,2 3,4 11,1 2 (5,6-R), (7,8-Y), (9,10-B) - ER IDMT NON-DIR TJM10, 2TJM10, TJM20, TJM11, 2TJM10, TJM21 Multi unit/Case 2O/C, E/F 1,2 3,4 11,1 2 (5,6-R), (7,8-E/F), (9,10-B) - Single unit/Case O/C 1,2 3,4 11,1 2 9,10 5,6 - ER IDMT DIR. TJM12, 2TJM12, TJM22 Single unit/Case E/F 1,2 3,4 11,1 2 9,10 5,6 -
ER IDMT NON-DIR E/F TYPE TJM60 Single unit/Case E/F 1,2 3,4 - 9,10 - - ER IDMTL PROGRAMME DCD, MIT Multi unit/Case 1,2 3,4 3,4 (5,6-R), ( 7,8-Y),(9,10-B), (11,12-E/F) - EE ALSTOM IDMT NON-DIR CDG11, 12,13,14 Single unit/Case 1,2 3,4 3,6 9,10 3,8 Multi unit/Case 3O/C 1,2 3,4 (5,6-R),( 7,8-Y), (9,10-B) - 3,12 OR20 EE ALSTOM IDMT NON-DIR CDG31, 32,33,34 CDG61, 62 Multi unit/Case 2O/C, E/F 1,2 3,4 (5,6-R), (7,8-E/F), (9,10-B) - 3, 12 OR20 EE ALSTOM IDMT DIR CDD 21, 23, 24,26 CDD 31,33,34,36 Single unit/Case 1,2 3,4 9,10 7,8 3,6 OR 20 EE ALSTOM DEF. TIME DELAY CTU32 Multi element/C ase 1,2 3,4 3,17 (5,6-R), (7,8-E/F), (9,10-B) - 19,20 30V DC EE ALSTOM INSTANT CAG11, 12,13,14, 17, 19 Single unit/Case 1,2 - 3,4 9,10 - - JVS IDMT NON-DIR JRC053 Multi element/C ase 11,1 2 13,1 4 - (1,2R),( 3,4 -Y), (5,6-B), (7,8-E/F) - 20,19
JYOTI IDMT NON-DIR Single unit/Case 9,10 11,1 2 - 7,8 - 1,2
ABB IDMT
NON-DIR ICM21P Single unit/Case 5,6 7,8 - 1,2 - 3,4 UE IDMT NON-DIR R-1156 Single unit/Case 9,10 1,2 - 7,8 - 1,4
3.7.2.9 CONTACTS, TERMINALS FOR DIFFERATIONAL RELAYS. CURRENT TERMINALS HT Side (COMMON) LT Side (BIAS) Operating Point M ak e T yp e S tan d ar d A lar m T ri p R Y B r y b R0 Y0 B0 A u x. V ol t D C 4C21 Single unit / Case 1,2 3,4 1 0 10 10 9 9 9 7 7 7 - 1+1 4+4 11+11 ER
DUO-BIAS M Multi unit /
Case
Module 2 (RL1, RL2) General Command
3 6 13 3 6 13
During Test both HT & LT Terminals to be shorted (Ex. 1+1)
220 V DC
ABB RADSB -do- 15, 16 17,18 6 7 8 3 4 5 12 13 14 1,2
DTH31 -do- 1,2 3,4 1 4 18 10 11 15 7 12 16 8 5- 110 V 6- 220 V 19- 30V 20 - --ve EE ALS TOM DTH32 -do- 1,2 3,4 7 17 27 10 20 30 8 or 9 Short (8 +9) 18 or 19 Short (18 + 19) 28 or 29 Short (28 +29) 11- 30 V 13- 110 V 15–220 V 12 - - ve DDT Single unit / Case 1,2 3,4 1 0 10 10 5 5 5 7 7 7 3- + ve 8 --- ve DDT Multi unit / Case 1,2 3,4 5 18 13 10 20 11 6 16 14 3- + ve 8 --- ve 27 27 27 MBCH 12 (2 Winding Single unit / Case 9, 11 1,3 2 5 25 25 23 23 23 Short (24 +26 +28) 13- + ve 14 -- ve 220 V EE ALS TOM MBCH 13 (3 Winding -do- 9,11 1,3 2 5 25 25 23 or 21 23 or 21 23 or 21 27 27 27 13- + ve 14 --- ve 220 V
4. DAT A ON ELECTRICAL SYSTEM EQUIPMENTS 4.1 BREAKERS TECHNICAL PARTICULARS Sl.no Particulars 33KV 132KV 220KV 400KV 1 System voltage (kv) 36 145 245 420 2 System frequency (H2) 50 50 50 50 3
Quenching medium Vacuum,
Oil
Oil, Air blast
SF6
Oil, Air blast SF6 (puffer)
SF6 (Puffer) Air blast
4
Operating medium Spring
Spring Hydraulic Air pressure Spring Hydraulic Air pressure Air Pressure Insulation standard 5
(a) Lightning Impulse voltage
(KVp) (1.2/50µ) 170 650 1050 1425 (b) Power frequency withstand
voltage (kv) 1min/50Hz) 70 275 460 520
( c) Minimum disruptive
voltage (kV) 28 105 176 320
6 Normal current (A) 1250 1250/1600 2000 2000/3150
7
Short time current withstand
capacity (KA)(3 sec) 25 40 40 40
Fault Rating
(i) Making capacity (KA)
70 100 100 100
(ii) Breaking capacity (KA) 25 40 40 40
(iii) Breaking current out of ph
(KA) 6.5 10 10 10
(iv) Rated time charging
current (A) 50 50 125 400 8
(v) Over voltage factor for
switching 3.0 3.0 3.0 3.0
Operating Sequence
(a) Normal O-10s-CO-3min-CO
9
(b) Auto Reclose O-0.3s-CO-3min-CO
10
TRV (Transient Recovery Voltage) First phase to clear
factor 1.5 1.5 1.3 1.3
Breaker operating time (i) Maxm break time (Open) ms 60 50 50 40
(ii) Maxm Close time (ms) 100 150 150 120
(iii) Maxm Close -Open time
(ms) - 80 80 60
(iv) Maxm time open interval
between 1st and last phase (ms) 5 3.3 3.3 3.3
11
(v) Maxm time close interval
4.2 CIRCUIT BREAKER
4.2.1 132 KV SF6 GAS CIRCUIT BEAKER Particulars Rating / Value Particulars Rating / Value Make Crompton Greaves Ltd. Nasik Rated Lightening impulse with Stand voltage 650 KVp Type 120-SFM-32 A Rated short Circuit Breaking Current 31.5 KA
Rated Voltage 145 KV Rated Operating pressure
15.5 KG/cm2 - g
Rated Frequency 50 HZ First pole to Clear factor 1.5 Rated Normal Current 3150 A Rated Duration of short Circuit current 31.5 KA 3 Sec Rated Closing Voltage 220 V DC Rated Line Charging Breaking Current Rated SF6 Gas pressure 50 A Rated Opening Voltage 220V DC Rated Voltage and frequency for Aux. Circuit
415 VAC 50 HZ GAS
PRESSURE SF6
6.0 bar at 20
0 c Rated operating Sequence 0-0.3S-
CO-3Min-CO Total weight with Gas 2000 KG Gas weight 9 KG Sl. No. 11583C STD. IEC 56 Month / Year of Manufacturing MARCH./ 99
4..2.2 220 KV SF6 GAS CIRCUIT BEAKER Particulars Rating / Value Particulars Rating / Value Make ABB Limited Rated Lightening impulse with Stand voltage 1050 KVp Type ELF SL 4-1 Rated short Circuit Breaking Current 40 KA
pressure KG/cm2 - g
Rated Frequency 50 HZ First pole to Clear factor 1.3 Rated Normal Current 2000 A Rated Duration of short Circuit current 40 KA 3 Sec Rated Closing Voltage 220 V DC Rated Line Charging Breaking Current Rated SF6 pressure 125 A Rated Opening Voltage 220V DC Rated Voltage and frequency for Aux. Circuit
1-PH (230V & 3 PH 415 VAC 50 HZ GAS PRESSURE SF6 7.0 bar at 20 0 c Rated operating Sequence 0-0.3S- CO-3Min-CO Total weight with Gas 3800 KG Sl. No. 307786 Month / Year of Mang MARCH./ 99
4. 2.3 33 KV VACUUK CIRCUIT BREKER Particulars Rating /
Value
Particulars Rating / Value
Make BHEL impulse with
Stand voltage
170 KVp
Type PVN 36 Short Time
Current
25 KA Rated Voltage 36 KV Rated Air
pressure Rated Frequency 50 HZ Making
Capacity 62.5 KAp Rated Normal Current 1250 A Sym. Breaking Capacity with Dur. 25 KA for 3 Sec Shunt Trip coil 220 V DC P.F With stand
V 70 KV Spring REL. Coil 220 V DC Spec. IS 2156/ IEC 56 Rated operating Sequence 0.3 Min. - CO Month / Year of Manufacturing April/1991 Sl. No. 9087652 TOTAL WEIGHT 1000 KG
4.2. CURRENT TRANSFORMER 4.2.1. SPECIFICATIONS
RATIO OF THE CT NUMBER OF CORES
RATED BURDEN AND FACTORS CLASS OF ACCURACY Items 33 KV In door 33 KV Out Door CT Rating No Of Cores Core Burden ( VA)
Factors Core Acc. Class Ratio Single Ratio Multi Ratio 33 KV 3 Cores (Metering, Protection , Diff.) Meterin g 2.5,5, 7.5,10, 15,30 METE RING 0.1, 0.2 0.5, 1, 3, 5 Primary Current Suitably (10,15,20,30 50,75) Multiple or Fraction 2.5,5, 7.5,10, 15,30 ISF (5, 10, 20) ALF (5,10,15,20, 30) Voltage Across CT = (Burden X ALF)/ Rated Current PROTE C TION (5P, 10P 15P) * Secondary Current 1A or 5 A 66 KV 5 Cores Metering Protection , Differenti al Bus Prot., Dist. Prot. Protecti on
Rated Short time Current
Ist = 150 Ip for 1 Sec.
SELE TIVE PROTE CTION PS * *
NOTES OF THE TABLE (4.2.1 ) ON THE NEXT PAGE. * Accuracy class is usually followed by ALF (5P10, 5P15, etc.)
** For accuracy Min. Knee Point Voltage (VK) and permissible Mag. Current (I mag) to be considered
NOTE 1: -VK = K Is (Rct + Rb), K= Parameter depends upon System fault level and characteristics of the Relay
Is = Sec. Reflected current
Rct = CT Sec. Resistance at 75 0 C Rb = Resistance of Sec. Circuit with Lead
NOTE 2: - Imag = P mA at V K / FM, Imag = Max Allowable Mag. Current (mA)
P mA = Permissible Magnetizing Current ( m A )
4.2.2 VOLTAGE CLASS AND INSULATION LEVEL Nominal System Voltage KV RMS Highest System Voltage KV RMS Power Frequency Withstand Voltage KV RMS Lightning Impulse Withstand Voltage KV PEAK Nominal System Voltage KV (RMS) Highest System Voltage KV (RMS Power Frequency Withstand Voltage KV RMS Lightning Impulse Withstand Voltage KV PEAK List 1 List 2 220 245 360 850 Upto 0.6 0.66 3 - - 395 950 3.3 3.6 10 20 40 460 1050 6.6 7.2 20 40 60 400 420 950 * 1175 11 12 28 60 75 1050 * 1300 33 36 70 145 170 1050* 1425 66 72.5 140 325 325 525 524 1050* 1425 110 123 185 450 1175* 1550 230 550 132 145 230 550 275 650
* Switching Impulse Withstand Voltage in KV (PEAK)
4.2.3 ERRORS IN CT
4.2.3.1 METERING CORE Acc.
Class
± % Current Ratio Error at % Of Rated Current
± Phase Angle displacement Error in
Minutes at % of Rated Current 1% 5% 20% 100% 120% 1% 5% 20% 100% 120% 0.1 - 0.4 0.2 0.1 0.1 - 15 8 5 5 0.2 - 0.75 0.35 0.2 0.2 - 30 15 10 10 0.5 - 1.5 0.75 0.5 0.5 - 90 45 30 30 1.0 - 3.0 1.0 1.0 0.2s 0.75 0.35 0.2 0.2 0.2 30 15 10 10 10 0.5s 1.5 0.75 0.5 0.5 0.5 90 45 30 30 30 4.2.3.2 PROTECTION CORE Acc. Class Current Error at Rated Primary Current (%) Phase displacement at Rated Primary Current
(Minutes) Composite Error at Rated Acc. Primary Current (%) 5P ± 1 ± 60 5 10P ± 3 - 10 15P ± 5 - 15
4.2.4 RELAY DETAIL FOR SELECTION OF INSTRUMENT TRANSFORMERS 4.2.4.1 TRANSFORMERS DIFFERENTIALS 4.2.4.1.1. ALSTOM MAKE 1 Relay type:DTH 31/32 V k >40*I (R CT +2R L );Example: V k >40(1)(3+4) >280V 2. Relay type: MBCH 12/13
V k >24 In (R CT +2R L ) Where V k =Knee Point Voltage In=Relay rated current, R L =Total Lead Resistance Ie=<3%In at V k /4 for both above types of relays i.e.0.03I i.e.30mA at V k /4
3. Relay type: KBCH, MiCOM P630 (Numerical)
Application Knee point
voltage V K
Through fault stability X/R
If Transformers, Generators,
Generator transformers, Motors, Shunt reactors, Series reactors also
24In [R CT +2RI ]
40 15In
Overall generator- transformer units,
48In [R CT +2RI
120 15In
Transformers connected to a mesh corner, having two sets of CTs each Supplying separate relay inputs. 48In [R CT +2RI 40 120 40In 15 In 4. 2.4.1.2 ABB MAKE
1. Relay type :RADSB (Static)(Medium impedance) V K >30(R CT +2R L +Rre) In , >30(4+4+3)1, >330V
Note: Over current factor of 30 recommended Excitation Current -Not applicable*
2. Relay type:SPAD346C (Stabilised diff. Relay) V K >4xI max x (R in +R L )/n,
Where, n =Transformation ratio of CT>(R CT +R L +0.5/sq.of Isn) Rin =Sec. Resistance of CT
2R L =Control cable (‘To &fro ’)resistance
3. Relay type:RET316 (Stabilised diff. Relay) n ’ ==n (Pr +Pe) / (Pb +Pe), Where, n =ALF
n ’ ==Effective over current factor, is a function of fault current
I k ,freq and time constant of network, and read from graph in RET manual Pb =connected burden at rated current, Pe =CT losses of sec windings Pr =rated CT burden, DC time constant assumed is 300msec
*Not Applicable :-Relay provided with ‘ Magnetizing Inrush Restraint ’ based on Second Har monic Content of the inrush current and hence ‘Imag ’ calculation is not applicable...
4. 2.4.1.3. EASUN REROLLE
1. Relay type:4C21 (Static)(Low impedance)
CT Class :PS, V K >2I f (R CT +R L +Rict (P))+(ICT V K x ICT ratio) Example: V K >2 x 10.9375 (2+3+1)+(14.43/ 0.875) x 0.577 >140.75 Volts R CT -Main CT resistance, Rict (P)-ICT primary winding resistance
R L -Lead resistance, I f -Max. thro fault current 2. Relay type: Duobias M(Numeric),
(Differential and Restricted Earth Fault)
V K >4xI(A+C), Where : I =Either max 3-phase through fault current referred to secondary (as limited by transformer impedance)or high-set setting, whichever is greater.
A =Sec. winding resistance of each star connected CT C =CT secondary loop resistance for internal faults. CT Class recommended-PS,X to BS 3938,TPS to IEC-44- 4. 2.4.2 GENERATOR DIFFERENTIAL PROTECTION 4. 2.4.2.1. ALSTOM
1. Relay type:CAG34 (High Impedance Scheme) V K >2I f (R CT +2R L )
Example :V K >2x10(3+4) >140V
Where ,I f =sec. equivalent of Fault Current Ie =Is-Ir =(0.15-0.10) /2 =25 m A at V K /2
2. Relay type: LGPG, MiCOM 340 (Numerical)
For voltage dependent, over current , field failure and negative phase, sequence protection V K >20In (R CT +2R L )
l For stator earth fault protection V K >Is (R CT +2R L +RR)
2.For generator differential protection: Low impedance diff. V K >50In (R CT +2R L ) High impedance diff V K >2 Vs
3.Relay type:YTGM15,YCG15AA,ZTO11(Generator Backup) V K >2If (R CT +2R L +M+CM), Where CM=connected burden
4. 2.4.2.2. ABB
1. Relay type: RADHA /RADHD (High impedance ) V K >2I K (R CT +R L ), >2x25(4+3), >350V,
R L in case of generator is longer i.e.2R L =6 Ohms
I K will be higher considering Xd ”(0.2 pu)and CT sec.of 5A
Excitation current -Not applicable * Excitation current is kept low for increasing the primary sensitivity
*Not Applicable :-Relay provided with ‘ Magnetizing Inrush Restraint ’ based on Second Har monic Content of the inrush current and hence ‘Imag ’ calculation is not applicable...
4. 2.4.2.3. EASUN REYROLLE
1. Relay type:4B3 (EM)/DAD 3 (Static)/Argus-1 (Numeric)(High Impedance Scheme)
V K >2I f (R CT +2R L ), Example: V K >2x10(3+4) >140 Volts CT Class :PS, I f -Max. thro fault current, R CT -Main CT resistance R L -Lead resistance between CT to relay.
2. Relay type: GAMMA (Numeric) (High Impedance)
For Two off 3 phase Inputs (Line end and Neutral end)and for Neutral Earthed CTs. In case of low impedance bias diff functions-
a)V K >50xIn(R CT +2R L +RR)
where max. through fault current=10xIn with max X/R=120. b)V K >30xIn(R CT +2R L +RR)
where max. through fault current=10xIn with max. X/R =60
In=Rated Current Sec. X/R=X/R ratio for max. through fault condition. R CT =Sec. resistance of CT, R L =Lead resistance between CT and Relay RR=Resistance of any other protection functions sharing the CT
4.2.4.3 BUS DIFFERENTIAL PROTECTION 4.2.4.3.1. ABB
1. Relay type: RADHA/RADHD (High impedance scheme) V K >2I K (R CT +R L ) , >2x40 (4+4) , >640 V
2. Relay type: RADSS (Medium impedance scheme) Depending on diff. ratios , For 1A CT, Vk shall be 500V.
Excitation Current -Not applicable*
*Not Applicable :-Relay provided with ‘ Magnetizing Inrush Restraint ’ based on Second Har monic Content of the inrush current and hence ‘Imag ’ calculation is not applicable...
4. 2.4.3.2. ALSTOM
1. Relay type:CAG34 (High Impedance scheme) V K >2I f (R CT +2R L ), Example: V K >2X10(3+4), >140V
2. Relay type: DIFB –DIFBCL
V K >K x In(RTCP+R F +Rd/n 2 ),
Where: K=(1.2/40)x(I CC /I N )
I N =Main CT primary rated current, I CC =Max short-circuit current delivered to bus bar via the input Where MCT is installed.
RTCP=Rest. of secondary of MCT, R F =Rest. of link loop between MCT and auxiliary CT, n=Ratio of auxiliary CT , Rd/n 2 =Value of differential resistance transposed to ACT primary
3. Relay type: MCTI 34 (Numerical)
V K >1.6V S , V S =1.25xI f (R CT +2R L )
Where: R CT =CT resistance, RL=Max lead resistance from CT to common point, I f =Max internal secondary fault current.
4.2.4.3.3. EASUN REROLLE
1. Relay type:B3 (EM)/DAD3 (Static) CT Class: PS , V K >2I f (R CT +R L )
Example: V K >2X10(3+4) >140V I f -Max. thro fault current
R CT -Main CT resistance
4. 2.4.4 DISTANCE PROTECTION 4. 2.4.4.1. EASUN REYROLLE
1. Relay type: THR (Static)
CT Class :PS, V K >Ix(R L +R 2 +X/Rx(R 3 +R 2 )) Example: V K >10(3.8+7+4(1.2+7)) >436V
Where: R L -Burden of relay (3.8 Ohm max.) R 2 -Resistance of leads plus resistance of CT sec.
X/R-Ratio of reactance to resistance of the system for fault at the end of zone 1 ,
R 3 -constant depending on impedance setting of zone 1. (1.2 Ohm max.) I-Sec. fault current for fault at end of zone 1
Note: X/R =4 for 132 kV system in above. =7 for 220 kV
=11 for 400 kV
2 Relay type: Ohmega (Numeric)
V K should be equal or greater than the higher of following two expressions. a)V K >K x(I P /N(1+X P /R P ))x(0.03+R CT +R L ) For phase-phase faults b)V K >K x(Ie /N(1+Xe/Re))x(0.06+R CT +R L ) For phase-earth faults I P -Phase fault current calculated for X P /R P ratio at the end of zone 1 Ie -earth fault current calculated for Xe /Re ratio at the end of zone 1 N -CT ratio.,
X P /R P -power system reactance to resistance ratio for the total plant including the feeder line parameters calculated for phase fault at the end of zone 1
Xe /Re -similar ratio to above but calculated for an earth fault at the end of zone 1
R CT -CT resistance, R L -lead burden CT to Relay
K -Factor chosen to ensure adequate operating speed which is >1.0 4. 2.4.4.2 ALSTOM
1. Relay type: Micromho, Quadrmaho V K >I f (X/R)(M+R CT +nR L )
Example: V K >10(4)(10.2+3+4) >40(17.2) >688V Ie <3%In at V K /2 <30 mA at V K /2
Where M=Relay resistance (Phase fault)
2. Relay type: MiCOM 430/441/442,EPAC,LFZR,LFZP, PD521,PD932 (Numerical)
V K >I f x(1+X/R)x(R CT +R L +R B )
Where: X/R=The primary system ratio. R B =Relay Burden
R L =Rest of cable connecting CT to relay (lead and return for ground faults, lead only for phase faults)
4. 2.4.4.3. ABB
1.Relay type:RAZAO/REL511 (Static)(Numerical)
Secondary limiting voltage>(Ik x Isn/ Ipn )x a x (R CT +R L +0.5/(Isn/Ipn)2 ) Where a =factor for the DC time constant (approx 10 for about 100msec) Excitation Current <0.2 Isn <0.2 A <200m
4. 2.4.5 FEEDER DIFFERENTIAL PROTECTION 4. 2.4.5.1. EASUN REYROLLE
1. Relay type :Solkor-M and Microphase-FM (Numerical) (Current Differential)
V K >k x X/R x I f /N x (R CT +2R L +R b ) Where: K =stability factor =0.8 for Micro phase-FM X/R =X/R ratio for the max through fault conditions.
(The value of this transient factor depends upon the sum of the source and transmission circuits impedances.)
R b =burden of relay, The ac burden of the relay per phase is 0.05VA at 1A,tap=0.05 ohms and 0.30 VA at 5A tap=0.012 ohms The values of magnetizing currents of CTs at two ends should not differ by more than In/20 for output voltages up to 50/In volts. 4.2.4.5.2. ALSTOM
1. Relay type: MBCI
Translay ‘S ’ Differential (For Feeder and Transformer) (A)For plain feeders:
V K >0.5xNxK1xIn(R CT +XR L )
Where: V K =KPV of CTs for through fault stability. R L =Rest. of CT secondary circuit.
X=1 for core wire connections between main CT and the relay and =2 for six wires connection
N =Relative neutral turns on summation transformer winding K1=The selected time-dependent constant
For all application at or above 220 kV where X/R ratio are large: V K >NxK1xIn(R CT +XR L )
Magnetizing current<0.05xIn at 10/In V (B)For transformer feeder differential:
a. V K >50xIn(2.2/In2+R CT +R L )-for star connected CTs. b. V K >50xIn/v3(9.7/In2+R CT +R L )-for delta connected CTs.
2. Relay type: MiCOM P540 (Numerical) V K >K *In (R CT +2R L )
Where: K is a constant depending on I f =The maximum value of through fault current for stability and is determined as follows:
For relays set at Is1 =20%,Is2 =2 In,k1 =30%,k2 =150%: K =40 +(0.07 x (I f x X/R))and
K =65 This is valid for (I f x X/R)<1000 In For higher (I f x X/R)up to 1600 In:
K =107
For relays set at Is1 =20%,Is2 =2 In,k1 =30%,k2 =100%: K =40 +(0.35 x (I f x X/R))and
K =65 This is valid for (If x X/R)<600 In For higher (I f x X/R)up to 1600 In: K =256
4.2.4.6 OVER CURRENT and EARTH FAULT RELAY 4.2.4.6.1. ALSTOM
1. Relay type:CDG11 (IDMT)
This relay has 3.5 VA burden. So total VA burden requirement is 10 or 15 VA.
ALF factor of 10 is sufficient
If backup protection scheme is envisaged, ALF of 15 is required. The time current setting characteristic of IDMT relay becomes straight line after 15 times setting; therefore, time discrimination is ineffective after 15 times current setting.
2. Relay type: MiCOM P120,P140 (Numerical) Class:5P10, Burden:5VA
4.2.4.6.2. ABB
1. Relay type: SPAJ 140 (Numerical)
This relay requires generally CT with 5P10/5P20 CT with very low burden.e.g.0.1 VA
4. 2.4.6.3. EASUN REYROLLE
1. Relay type: ARGUS /MIT (Numerical) Class: 5P10, Burden: 5 VA
2. Relay type: Solkor-R /RF (Pilot Wire Differential Protection) CT class: PS V K =50/ In + (I f / N) (R CT +R L)
In -Rated Current
I f -Maximum primary steady state through fault current N -CT ratio, R CT -CT resistance, R L -Lead Resistance
4.2.5 CURRENT TRANSFORMER ( NAME PLATE DETAILS )
4.2.5.1 132 KV CURRENT TRANSFORMER
Particulars Rating / Value Particulars Rating / Value
Make HIVOLTRANS ELECT. PVT.
LTD
Type CB-14
Ref. Standard IS 2705-1992 Normal Sys.
Voltage
132KV Rated Pri. Current 600-300-150 A Highest Sys.
Voltage 145KV Insulation Level ( Kv ) 275 RMS/ 650 PEAK S.Ty.Current Ka/Sec 18.2/3 Frequency 50 HZ Wt. Of Oil /Ct Kg 120/550
Min. Creep age 3625 mm Drg. No
0-325/CB-14/B/2031
Sl. No 0-325/B/1 Suitable For Hotline Washing
CAUTION
1. Sec. Terminals Must Be Shorted Before Burdon Is Disconnected 2. P.F. Testing Terminal to Be Earthed During Operation.
CORE RATIO/ AMP. SEC. CONNE CTION RATED VA ACC. CLASS Vk (V) Min I exc@Vk (mA) MAX Rct at 75 0 C Max 1 600/1 1s1-1s3 - PS 1200 10 5.0 300/1 1s1-1s2 - PS 600 20 2.5 150/1 1s1-1s2 - PS 600 20 2.5 2 600/1 2s1-2s3 (S1-S3) 15 0.5 Fs<5 - - - 300/1 2s1-2s2 (S1-S2) 15 0.5 Fs<5 - - - 150/1 2s1-2s2 (S1-S2) 15 0.5 Fs<5 - - - 3 600/1 3s1-3s3 - PS 1200 10 5.0 300/1 3s1-3s2 - PS 600 20 2.5 150/1 3s1-3s2 - PS 600 20 2.5 1s1 1s2 1s3 2s1 2s2 2s3 3s1 3s2 3s3
4.2.5.2 220 KV CURRENT TRANSFORMER
Particulars Rating / Value Particulars Rating / Value
Make W.S INDUSTRIES Type IT-245
Ref. Standard IS 2705-1992 HSV/NSV 245/ 220 KV
BIL 1050/460 KV S.T.Current 40/ 1 KA/Sec
Frequency 50 HZ Wt. Of Oil 350 KG
Making Capacity 100 KAp TOTAL WEIGHT 1200 KG Sl. No/YEAR 5643/1997 RATIO 400-200-100/1-1-1-1-1 PRI/SEC CURRENT (A) 400/1 200/1 100/1 PRI. CONN. P1C1– P2C2 C1-C2 C1-C2 SEC. CONN. CORE 1 1S1-1S3 1S1-1S3 1S1-1S2 CORE2 2S1-2S3 2S1-2S3 2S1-2S2 CORE3 3S1-3S3,S’ 3S1-3S3,S’ 3S1-3S2,S’ CORE4 4S1-4S3 4S1-4S3 4S1-4S2 CORE5 5S1-5S3 5S1-5S3 5S1-5S2 CORE 1 2 3 4 5 OUT PUT* - - 40 - - ACC. CLASS* PS PS 0.5 PS PS ISF/ALF* - - 5 - - Vk (V) Min* 1200 1200 - 1200 1200 I exc@Vk *(mA) Max * 25 25 - 25 25 Rct at 75 0 C Max* 5 5 - 5 5
* AT 400/1 AND 200/1 RATIO ONLY P1 C2
C1 P2
2.3 33 KV CURRENT TRANSFORMER Particulars Rating / Value Particulars Rating / Value Make GYRO LAB PVT. Type GWT-0/33 Ref. Standard IS 2705-1992 Frequency 50 HZ Ratio 400-200- 100/1-1-1A Highest Sys. Voltage 36 KV Insulation Level 70/170 KV S.T.CurrentKA/Sec 25 KA / 1 Sl. No 3452 CORE RATED VA ACC. CLASS SF Vk (V) Min I exc@Vk (mA) mAX ISF Rct at 75 0 C Max I 30 5P 10 - - - II 30 0.5 - - - < 5 - III - PS 1000-1200 25/ 15 <3 /<6 CONNECTION DIAGRAM
RATIO PRIMARY CONN. SEC. CONN.
100/1 C1+C2 S1-S2 200/1 P1+C1 & P2 +C2 S1-S2 400/1 P1+C1 & P2 +C2 S1-S3 P1 C2 C1 P2 S1 S2 S3
4. 2.6 FAULT FINDING STUDY FOR STAR CONNECTEDCT PROTECTION CIRCUITRY
Sl . No
Current in the CT secondary Expected Faults
1 R=Y=B= x Amp
N= 0 Amp
No Fault in the circuits R=Y=B= x Amp
& N= 2x Amp
ANY ONE OF THE PHASE ‘ CT’ POLARITY REVERSED i. If (R+Y ) = ( Y + B ) = 3x & ( B + R )= x Y PHASE REVERSED ii. If (R+Y ) = ( B + R ) = 3x &( Y + B ) = x R PHASE REVERSED 2 iii. If (Y+B ) = ( B + R ) = 3x &( R +Y ) = x B PHASE REVERSED I. If R = 0 Amp & Y = B= N = x Amp
Then Check for all other R phase CT secondary cores, if values obtained as
If R = 0 Amp
& Y = B= N = x Amp
R PHASE PRIMARY SIDE OPEN
II. Similarly for Y phase and B Phase also. CORRESPONDING PHASE PRIMARY SIDE OPEN
III. If R = 0 Amp & Y = B= N = x Amp For only in One core, Then
R PHASE SECONDARY IS SHORTED OR
R PHASE IS MIOXED WITH OTHER CORES
OR
FOR USE OF AUX. CT , ANY ONE OF THE SIDE MIGHT BE SHORTED.
3
IV. .Similarly for Y phase and B Phase also. CORRESPONDING PHASE
4 R=Y=B= x Amp
N= 3x Amp
All phases have been connected to one CT only instead of different cores as 1st , 2nd 3rd cores etc. As R phase cores and Y phase cores
and B phase cores OR
Primary Side has been connected from a Single Source
I. R=Y= x/2 Amp,B= x Amp N= 0 Amp
R & Y phases of CT Secondary similar polarities have been shorted. II. Y=B= x/2 Amp,R= x Amp
N= 0 Amp
Y & B phases of CT Secondary similar polarities have been shorted. 5
III. B=R= x/2 Amp, Y= x Amp N= 0 Amp
B & R phases of CT Secondary similar polarities have been shorted. I. R= x Amp., R=B= 0 Amp.
N=x Amp.
Y & B phases of CT Secondary have been shorted.
II. Y= x Amp. Y=B= 0 Amp. N=x Amp.
B & R phases of CT Secondary have been shorted.
6
III. B= x Amp. R=Y= 0 Amp.
N=x Amp
R & Y phases of CT Secondary have been shorted.
7 R=Y=B=N=0Amp All the 3 CTs are shorted.
8 If the values are resulted other than the above readings as described.
1.CTR may be different
2.Wrong primary link connection 3.Phase angle problem
4.3. VOLTAGE TRANSFORMER 4.3.1 SPECIFICATIONS
RATIO OF PT RATED
BURDEN
CLASS OF ACC.
ITEM 22 KV 33 KV Winding Acc.
Class UNIT Multi phase in single unit 3 Single phase PT in star connection separate Winding Connection
Y/Y, V/V Y/Y, Y/Y – Open delta Metering 0.1, 0.2, 0.5, 1.0, 3. Primary Voltage Rated Voltage / 3 Secondary Voltage 110V / 3 1. The Rated Burden at a P.F = 0.8 (lag) shall be chosen as (10, 25, 50, 100, 200, 400, 500) VA / Phase for 3 Phase Transformer 2. Two independent Secondary Windings are to be Provided for Metering & Protection Core Protection 3P, 6P 4.3.2 ERRORS IN PT
METERING CORE PROTECTION CORE
ACC. Class ± % Voltage Ratio Error ± Phase Angle displacement Error in Minutes ACC. Class ± % Voltage Ratio Error ± Phase Angle displacement Error in Minutes 0.1 0.1 5 3P 3 120 0.2 0.2 10 6P 6 240 0.5 0.5 20 1.0 1.0 40 3.0 3.0 -
Note. Errors at any Voltage between 80 to 120 % of rated voltage, with Burdens
between 25 to 100 % of rated burden at p.f 0. 8 (lag)
Note 1. Errors at 5 % rated Voltage and Voltage multiplied by voltage factor (1.2, 1.5 or with burdens Between 25 to 100 % of rated burden at p.f 0. 8 (lag)
Note 2: - Errors at 2 % rated Voltage shall be twice as high as given in the table with similar burdens to Note 1.
4.3.3 POTENTIAL TRANSFORMER ( NAME PLATE DETAILS ) 4.3.3.1 132 KV CAPACITOR VOLTAGE TRANSFORMER (1 PH)
Particulars Rating / Value Particulars Rating / Value
Make CGL Sl. No. 02314
Type VCE :145/275/50 Rated Voltage 132 KV/ 3 KV Highest System Voltage 145 KV Rated Insulation Level 275/650 KV Total WEIGHT 420 ± 10 % KG Rated Frequency 50HZ CAP. OIL 25 ± 10 % KG Standard IS 3156 EMU OIL 85 ± 10 % KG HV ( Pri)
Capacitance 6511+ 10% - 5 % pF Int. V ( Sec ) Capacitance 35418 + 10% - 5 % pF Equ. Cap ( Cn ) for PLCC 5575+ 10% - 5 % pF Nom. Interme.Volt. 13 KV TOTAL SIM. BURDEN/CLASS 150 VA / 0.5 Total Thermal Burden 300 VA Month / Year of Manufacturing MARCH./ 98 Voltage Factor 1.2 Continuous / 1.5 for 30 Sec
1 ph solidly earth Connection
Rated Sec. Voltage Terminal Marking Rated burden VA Acc. Class
110/ 3 V 1a-1n 100 0.5
110/ 3 V 2a-2n 100 3P
4. 3.3. 2 33 KV POTENTIAL TRANSFORMER ( 1 PH )
Particulars Rating / Value Particulars Rating / Value
Make GYRO LAB PVT. Type GWT-0/33
Ref. Standard IS 3156 ( PT I,II,III ) SL. NO 4536 Ratio 33/ 3 KV/ 110/ 3 V Insulation Level 70/170 KV Voltage Factor 1.2 Continuous /
1.5 for 30 Sec
Highest Sys. Voltage 36 KV
CORE RATED VA ACC. CLASS TERMINAL MARKING W1 100 0.5 1a-1n W2 100 0.5 2a-2n
4.3.3.3 220 KV CAPACITOR VOLTAGE TRANSFORMER (1 PH)
Particulars Rating / Value Particulars Rating / Value
Make ABB Limited Sl. No. 2204147
Type WP 245N2 Rated Voltage 220/ 3 KV
Highest System Voltage 245 KV Rated Insulation Level
245/460/1050 KV Total Creepage 6125 min. nom.mm Rated Frequency 50 HZ
Wt of Oil 140 KG Standard IEC : 60186/ IS :
3156
Total Weight 750 KG HV ( Pri)
Capacitance
4840 pF Int. V ( Sec ) Capacitance 48400 pF Equip. Cap
( Cn ) for PLCC
4400 + 10 % - 5 % pF Nom. Intermediate Volt. 20/ 3 KV Temp. category - 5 to 55 0 C Total Thermal Burden 750 VA Class of Insulation A
1 ph solidly earth Connection Suitable for hot Line Washing Month / Year of
Manufacturing
MARCH./ 99 Voltage Divider ratio
220/ 3 KV/20/ 3 KV
Voltage Factor 1.2 Continuous / 1.5 for 30 Sec
G.A Drg. No. 1HYT900158-013
Rated Sec. Voltage Terminal Marking Rated burden VA Acc. Class
110/ 3 V 1a-1n 150 0.5
110/ 3 V 2a-2n 150 3P
4.4 LIGHTNING ARRESTER
4.4.1MAXIMUM SWICHING SURGE LEVEL IN pu (pu = 2 V line (max) / 3)
Highest System Voltage KV, RMS Typical Switching Surge pu Highest System Voltage KV, RMS Typical Switching Surge pu 12 KV – 36 KV < 4 525 KV 2.25 123 – 145 KV <3 765 KV 2.0 245 KV 3 1500 KV 1.5 (Projected) 420 KV 2.5
4.4.2 TECHNICAL PARTICULARS OF STATION CLASS ARRESTERS FROM 11 TO 33 KV
(AS PER IEEMA 20-2000)
System Voltages in KV Sl. No Particulars 11 11 11 11 22 22 33 33 1 Rating KV (RMS) 9 9 9 9 18 18 30 30 2 MCOV (RMS) 7.2 7.2 9.6 9.6 15 15 25 25 3 Discharge Current 10 KA
4 Line Discha. Class 1 2 1 2 1 2 1 2
Rated frequency 50HZ
a) IR at MCOV Less than 400 micro Amps.
5
b) IG at MCOV About 1200 micro Amps.
a) Reference Current, mA 1 to 5 mA
6
b) Reference Volt at Reference Current
Greater than Rated Voltage Max. RDA (KV p) at a) 5KA 27 26 36 33 51 52 90 86 b) 10KA 30 28 38 36 60 56 95 90 7 c) 20 KA 34 30 42 40 68 60 105 100
Max. Switch IMP R V (KVp
500A 24 22.4 30.4 28.8 48 44.8 76 72
8
1000A - - - -
9 Max. Steep Current Impulse RDV (KVp)
36 34 42 40 60 56 105 100
10 High Current Impulse Withstand 100KAp TOV (KVp) i) 0.1 Sec 15 16 21 21 32 32 53 53 ii)1.0 Sec 15 15 20 20 30 30 51 51 iii) 10.0 Sec 14 14 19 19 29 29 49 49 11 iv) 100.0 Sec 13 13 18 18 28 28 47 47
Insulation Withstand
a) Lightning IMP 75 75 75 75 125 125 170 170
b) Power frequency 28 28 28 28 50 50 70 70
12
c) Switching IMP - - - -
13 Partial Discharge Less than 50 pC
14 PR Relief Class Class A
15 PR Relief Class KA (RMS) 40 KA
16 Total creepage Distance in mm
270 270 300 300 600 600 900 900
17 Max. Cant. Strength in KGM
325 325 325 325 325 325 325 325
4.4.3 TECHNICAL PARTICULARS OF STATION CLASS ARRESTERS FROM 132 TO 400 KV System Voltages in KV Sl. No Particulars 66 66 110 132 220 220 400 400 1 Rating KV (RMS) 60 60 96 120 198 216 360 390 2 MCOV (RMS) 51 51 81 102 168 175 292 303 3 Discharge Current 10 KA
4 Line Discha. class 2 3 3 3 3 3 3 3/4
Frequency 50HZ
a) IR at MCOV Less than 400 µAmps. Less than 500 micro Amps.
5
b) IG at MCOV About 1200 µAmps. About 1500 micro Amps.
a) Reference Current, mA 1 to 5 mA
6
b) Reference Volt at Reference Current
Greater than Rated Voltage Max. RDA (KV p) at
a) 5KA 170 160 251 320 518 567 820 860
b) 10KA 180 170 272 340 550 600 880 950
7
c) 20 KA 200 119 307 380 610 668 925 1000
Max. Switch IMP R V (KVp
500A - - - -
8
1000A 144 136 217 272 455 496 830 850
9 Max. Steep Current Impulse RDV ( KVp)
200 190 298 372 600 654 1000 1050
10 High Current Impulse withstand 100KAp TOV (KVp) i) 0.1 Sec 106 106 170 212 350 382 636 689 ii)1.0 Sec 102 102 163 204 336 366 610 661 iii) 10.0 Sec 98 98 156 195 322 351 585 634 11 iv) 100.0 Sec 94 94 149 187 308 336 560 607 Insulation Withstand a) Lightning IMP 325 325 550 650 1050 1050 1425 1425 b) Power frequency 140 140 230 275 460 460 630 630 12 c) Switching IMP - - - 700 1050 1050
13 Partial Discharge Less than 50 pC
14 PR Relief Class Class A
15 PR Relief Class KA RMS) 40 KA
16 Total creepage Distance in mm 1800 1800 3075 362 5 6125 6125 1050 0 10500 17 Max. Cant. Strength in
KGM
500 500 500 100
0
1000 1000 1000 1000
4.4.5 CLASS III LIGHTINING ARRESTER
TECHNICAL PARTICULARS Ref. Standard IEC 99-4, 1999
Sl.No Particulars Unit 36 KV
72.5 KV 145 KV 245 KV 1 System BIL KVp 170 325 650 1050 2 Rated voltage (RMS), (system voltage x 2) 3 KV 30 60 120 198 3
Max. Continuous operating voltage
(MCOV) KV 25 52 102 168
4 Nominal Discharge current (NDC) KAp 10 10 10 10
5 High current with stand KAp 100 100 100 100
PROTECTION LEVELS
(A) Impulse residual voltage (KVp)
(i) Steep current @ NDC 94 185 380 600
(ii) Lightning current
@ 0.5 NDC 80 156 330 510
@ 1.0 NDC 84 165 350 550
@ 2.0 NDC 94 185 390 610
(iii) Switching current @ 1 KAp 70 136 290 450
(B) Temp. Over voltage (KVp)
(i) For 0.1 sec 60 120 254 404
(ii) For 1 sec 55 111 234 372
(iii) For 10 sec 52 105 222 353
6
(iv) For 100 sec 51 102 215 31
INSULATION DATA
(i) Wet Power freq. Withstand KV 70 140 275 460
(ii) Dry lightning impulse KVp 170 325 650 1050
7 (iiI) Creepage mm 900 1800 3625 6125
OVERALL DIMENSION
(i) Outer Dia mm 280 280 280 280
(ii) Height mtr 0.68 0.940 1.540 2.785 8 (iii) Weight Kgs 45 60 150 250 MOUNTING ARRANGEMENT (i) PCD mm 368 368 368 368 (ii) No of holes 4 4 4 4 9
(iii) Dia of holes mm 15 15 15 19
10 Terminal connector
(I) Suitable conductor ACSR Single
zebra Single Panther (66 & 132kv) Single rabbit
4. 4.5 CLASSIFICATION OF OVER VOLTAGE & SURGE IMPENDANCE ( L/ C)
CLASSIFICATION OF OVER VOLTAGE SURGE IMPENDANCE
( L/ C) Particulars Temporary Over Voltage Switching Over Voltage Lightning Over Voltage Objects Surge Impedance ( L/ C) Magnitude 1 to 2 pu 1.5 to 5 pu Hundreds of KV to Several Tens of MV Tower Z T = 100 to 150 Ohm Duration mS to Tens of Sec. Tens of S to Tens of mS
Few Tens to Hundred of S. OH Ground Wire Z G = 400 Ohm Effect P.D. causes retardation of life of insulation Partial Discharge on Insulation Influences Transformer
Insulation and Break down of Weaker Section OH Phase Conductor Z T = 325 to 400 Ohm Testing Evaluation -- 250 ± 100 S 2500 ± 100 S 1.2 S ± 30% 50 S ± 20% Source Surge Impendance Z T = 1500 to 3000 Ohm
4.4.6 LIGHTNING ARRESTOR CLASSIFICATION
Long Duration Current Range of Voltage Impulse Current
KA 8x20 Micro Sec. High Current Magnitude (A ) Duration ( Micro Sec ) Low Voltage or Secondary Arrestor (175 to 660 V) 2.5 25 50 1000 Distribution Class (3 KV to 18 KV) 5.0 50 75 1000 Intermediate Class (3 KV to 110 KV) 5.0 50 75 1000 Station Class (light Duty) (11 KV to 198 KV) 10.0 65 150 2000 Station Class (Heavy Duty) (198 KV and above) 10 15 20 65 300 3000
4.5 WAVE TRAP
TECHNICAL PARTICULARS OF 0.5 mH/1250 Amp WAVE TRAP FOR 220 KV LINE
Particulars Value
Type Out door, Air Cored,
Air Cooled Continuous Current Rating at 50 0 C
ambient
1250 Amp Continuous Current Rating at 65 0 C
ambient
1125Amp Max. Symmetrical Short Circuit Current
For 1 Sec
31.5 KA Asymmetrical peak value of first half of
rated short time Current
80.5 KA
Rated Inductance 0.5 H
Blocking Range 150-500 KHz
Min. Resistive Component in Blocking frequency range
570 Ohm Radio Interference voltage < 500 µ V
Mounting Suspension
Basic Insulation Level 32.37 KVp
Standard Nominal Discharge Current for 8/20 micro Sec. Wave impulse
10 KA Rated Voltage of Arrestor 6 KV Max. 1.2/50 micro sec. Impulse Spark over
voltage
21.6 KVP Min. value of power frequency Spark over
voltage
9 KV rms Virtual steepness and max. Front of wave
Impulse Spark over voltage
49.8 KV / micro S 24.9 KVp
Tuning Broad Band
Visual Corona Extinction Voltage 156 KV Max. Residual Discharge Voltage for 8/20
micro Sec. Impulse Discharge current 1. 5000 A
2. 10000 A
21.6 KVp 21.6 KVp No of Turns in Main coil 28 (2 in Parallel
4.6 ISOLATORS
TECHNICAL PARTICULARS FOR 245 KV ISOLATOR
Particulars Value
Type Air break, Off load
Standards used 1SS 9921/85
Highest System Voltage 245 KV Nominal System Voltage 220 KV Max. Continuous Current Rating 2000 Amp Rated Short time Current for 3 Sec 40 KA
Max. Magnetizing current 0.7 A at 0.15 p F Rated Peak Short time Current 100KAp
1.2/50 µ Sec. Impulse Withstand Voltage
1200 KV Radio Interference voltage 1000 µ V Earthing SWITCH Rated Current
Capacity
50 % of Main switch Minimum Clearance in
1. Between Live parts and ground 2. Fixed Contact and blade in Open
condition 2400mm 1600mm Operating Time 1. Opening 2. Closing 10-12 Sec 10-12 Sec Continuous Rating of Aux. Contact 10 A
Temp. Rise 55 above Ambient
Insulation Level 530 KV
4.7 TRANSFORMER
4.7.1. CURRENT RATING OF TRANSFORMER (3~ΦΦΦ) Φ Thumb rule Current = (600 x MVA)/ KV
Actual rule Current = (575 x MVA) / KV Where MVA = Rating of Transformer KV = Rated voltage of transformer
Supply voltage, Rated voltage (KV) ACTUAL Current / MVA THUMB RULE Current / MVA THUMB RULE Current / MWatt (for cos =0.9 ) 11 33 66 132 220 400 52.3 17.43 8.72 4.36 2.615 1.44 54.55 18.2 9.1 4.55 2.73 1.5 60 20 10 5 3 1.66
