is there any difference in reading or error in value, if we
connect the R phase in Y terminal and Y phase in R terminal
of electronic energy meter of 11 kv feerders???
RELAY
1. REF RELAY :
• OPERATION WITH CT CURRENT FLOW DIRECTION.
• WHY REF RELAY WHEN DIFFERENTIAL RELAY IS THERE.
• REF RELAY STABILITY CHECK BY PRIMARY INJECTION –
WHICH POINT FOR CUR RENT INJECTION.
• WHY REF RELAY NEED STABILISING RESISTOR. IF
RESISTOR SHORTED OR BYPASSED, WHAT WILL HAPPEN.
• WHICH TYPE OF RELAY FOR REF, HIGH IMPEDANCE OR LOW
IMPEDANCE.
• IF NEUTRAL CT IS NOT CONNECTED IN THE CIRCUIT, WHAT
WILL HAPPEN.
• REF PROTECTION ACTS ON WHICH OF FOLLOWING:
SINGLE PH. TO E/F; PH-PH TO E/F; THREE PH. TO E/F.
2. DISTANCE RELAY :
• BASIC PRINCIPLE AND TYPES
• SWITCHED MODE PROTECTION – WHY IS IT CALLED SO.
• SCHEMES USED
• WHY ZONE-1 SET AT 80%
• SETTING RANGE FOR ZONE-2 AND ZONE-3
• HOW SINGLE PHASE TO GROUND FAULT MEASUREMENT IS
DONE.
•
3. WHAT IS POLARITY. CT LOCATION IF INTERCHANGED WHAT
WILL HAPPEN.
4. SOLKOR RELAY:
1. WHY SOLKOR IS USED.
2. CIRCUIT DIAGRAM OF SOLKOR RELAY
3. DIFFERENT PARTS OF RELAY
4. HOW IT WORKS.
5. EXPLAIN BY VECTOR DIGRAM.
6. WHAT ADVANTAGE FOR USING SUMMATION TR.
7. DIFFERENCE BETWEEN R & RF WITH CIRCUIT.
8. ADJUSTMENT OF PADDING RESISTANCE.
9. WHAT IS LEAKAGE CURRENT AND HOW TO MEASURE.
10. WHAT HAPPEN IF LINK IS LEFT OPEN.
11. 5KV/15KV INSULATION TR. ARE USED IN WHICH SYSTEM.
12. WHAT PRECAUTION TAKEN DURING TESTING.
Relay Page 1 of 5
13. PROCEDURE BEFORE TESTING AND AFTER NORMALISATION.
14. HOW RELAY IS TESTED IN LIVE CONDITION.
15. RANGE OF SPILL CURRENT ANS SETTING OF RELAY
16. IF MEASURED CURRENT IS 5MILLI AMPS, CAN RELAY
OPERATE.
17. EACH FAULT APPROXIMATE VALUE OF PICK UP.
18. WHAT IS THE REASON SOLKOR-R MODE PILOT SHORTED
CONDITION RELAY CURRENT PRESENT.
19. AFTER SHUTDOWN, WHY NEED TO OPEN SOLKOR PILOT, IF
NOT WHAT WILL HAPPEN.
20. AFTER NORMALISING WHAT CURRENT TO BE MEASURED, WHAT
IS ACCEPTABLE LIMIT.
21. WHAT HAPPENS IF PILOT OPENS FROM RELAY, WHEN FEEDER
IS LOADED.
22. CAN WE USE THIS RELAY AS O/C OR E/F RELAY.
23. ANY RELAY OTHER THAN PILOT CABLE TYPE.
24. IF FEEDER TRIPS ON SOLKOR, WHAT TO DO.
25. WHAT HAPPENS IF PILOT POLARITY REVERSE.
26. WHAT HAPPENS WHEN CT SHORTED AT ONE END.
27. WHAT HAPPENS IF PILOT SHORTED – STATUS OF RELAY
28. WHAT HAPPENS TO RELAY ,IF POWER CABLE GETS OPEN.
29. WHAT HAPPEN IF PADDING RESISTOR IS SHORTED AT ONE
END.
5. TR. DIFFERENTIAL:
1. CIRCUIT DIAGRAM
2. DIRECTION OF FAULT CURRENT.
3. WHEN THE FAULT IS IN ZONE AND OUT OF ZONE.
4. CT CONNECTION IN PY. AND SY. SIDE.
5. BIAS SETTING AND BIAS CURRENT.
6. WHICH BIAS SETTING USED IN TRS. FOR HIGHER TAPS.
7. PURPOSE OF RESTRAINING BIAS COIL.
8. WHY BIASING REQUIRED.
9. EXPLAIN IPCT, FOR EXAMPLE, DYN10 VECTOR GROUP. WHY
MATCHING TR. USED.
10. WHY NEED 2ND HARMONIC BLOCKING DURING INRUSH.
11. WHICH HARMONIC IS MORE 2ND OR 3RD.
12. HOW TO AVOID FALSE TRIPPING IN DIFF. PROTECTION WHEN
INRUSH CURRENT FLOW DURING TR. IS ENERGISED.
Relay Page2 of5
6. DIRECTIONAL RELAY:
1. CIRCUIT FOR USE OF DIRECTIONAL PROTECTION SYSTEM.
2. WORKING ZONE / NON-WORKING ZONE.
3. HOW THE CORRECT DIRECTION OF FLOW OF CURRENT IS
DETERMINED.
4. CT & PT CONNECTION DIAGRAM.
5. SETTING OF PHASE & EARTH FAULT ANGLE AND
OPERATING REGION.
6. WHICH DIRECTION IT IS PROTECTING.
7. WHAT PROTECTION AVAILABLE FOR POWER TR.
8. WHY CT CONNECTION IS STAR, IF TR. WINDING IS DELTA.
9. DIFFERENCE BETWEEN REF AND DIFF. RELAY
10. WHERE IS O/C & E/F RELAY CONNECTED EITHER HV SIDE
OR LV SIDE AND HOW E/F RELAY WORKS IF TR. WINDING IS DELTA
CONNECTED.
11. IN DELTA WINDING OF TR., IF ONE WINDING IS CUT AND
NOT EARTHED, WHICH PROTECTION WILL ACT.
12. IF DIFF. & REF RELAY ARE NOT WORKING, WHAT IS BACK
UP PROTECTION IN TR.
13. WHAT IS PURPOSE OF NGR AND HOW STANDBY E/F RELAY
WORKING, TESTING PRECAUTIONS IF COMMON NGR IS USED.
14. WHAT IS PROTECTIVE ZONE OF STANDBY E/F RELAY.
15. WHAT ARE PROTECTION AVAILABLE FOR FEEDER.
16. AFTER TR. IS NORMALISED, WHAT CURRENT TO BE
MEASURED.
17. BUSBAR PROTECTION:
a. BASIC PRINCIPLE AND DIAGRAM WITH CURRENT DIRECTION.
b. WHY OVER LAPPING CT’S REQUIRED, IF NOT WHAT WILL BE
THE EFFECT.
c. WHY CT SUPERVISION REQUIRED, HOW TRIPPING IS
AVOIDED, WHAT IS CT SUPERVISION SETTING VALUE.
d. HIGH IMPEDANCE & LOW IMPEDANCE TYPE
e. TEST PROCEDURE(STEP BY STEP)
f. AFTER NORMALISING, SPILL CURRENT VALUE AND LIMIT.
Relay Page3of5
18. CIRCUIT BREAKER FAILURE – FUNCTION, WHY NEEDED, HOW
TRIPPING ARRANGEMENT.
19. WHY INSTANTANEOUS ELEMENT IS NOT USED IN THE
NETWORK.
20. WHEN FEEDER IS LIVE AND BY MISTAKE LINE EARTH
SWITCH IS CLOSED, WHICH RELAY OPERATES – O/C OR E/F.
21. DURING TR. SWITCHING ON, IF DIFF. RELAY IS BLOCKED
BY 2ND HARMONICS, WHAT ARE THE OTHER PROTECTION IN SERVICE.
22. WHICH OF FOLLOWING PROTECTION OPERATES FAST, WHEN
11KV CABLE COMPARTMENT GET FLASH OVER: CABLE DIFFERENTIAL;
OVERCURRENT & EARTH FAULT; ARC PROTECTION.
23. WHICH PROTECTION OPERATES WHEN ANY ONE OF THE OHL
PHASE IS CUT AND HANGING, NOT TOUCHED WITH EARTH.
24. WHAT ARE DIFFERENT TTB ALARMS – HOW YOU KNOW THERE
IS ANY ALARM.
25. WHAT IS CIRCULATING CURRENT AND HOW IT WILL COME.
26. IF ONE TR. TRIPPED ON DIFF. RELAY WHAT YOU WILL DO.
27. IF SUB-STATION TRIP ON BUSBAR PROTECTION, HOW YOU
WILL RESTORE.
28. WHAT IS CT SATURATION. HOW IT IS CARRIED OUT.
29. D.C EARTH FAULT – HOW YOU WILL FIND OUT.
Relay Page 4 of5
30. PILOT WIRE SUPERVISION – HOW IT WORKS
31. IN 11KV SWITCHGEAR DBB SCHEME, ONE E/F RELAY IS
FAULTY IN ONE FEEDER AND THERE IS NO SPARE FEEDER – HOW YOU
WILL NORMALISE THE FEEDER.
32. WHICH PROTECTION IS USED FOR LONG CABLE FEEDER
33. DIFFERENCE BETWEEN TRAFO. DIFF. AND CABLE DIFF.
PROTECTION.
34. WHAT TYPE CHARACTERISTIC AVAILABLE FOR O/C AND E/F
RELAY.
35. WHAT IS THE DIFFERENCE BETWEEN STATIC AND ELECTRO-
MECHANICAL O/C RELAYS.
36. WHAT IS DEAD ZONE
37. HOW TRIPPING OF OTHER ZONE AVOIDED WHEN BUS
SECTION CB IN OPEN CONDITION FOR DEAD ZONE FAULT.
38. IF OUT OF STEP ALARM COMES WHILE ALL TR. IN SAME
TAP POSITION, WHAT YOU WILL DO.
39. WHAT YOU WILL DO IF AN 11KV FEEDER FAILED TO TRIP
ON: O/C or E/F or SOLKOR.
HOW YOU RESTORE THE SUPPLY.
Relay Page 5 of5
SWITCHGEAR
1. WHAT IS THE PROBLEM, IF A CIRCUIT BREAKER IS NOT
CLOSING.
2. IF AUTO TRIP IS OPERATED, CAN YOU CLOSE THE BREAKER.
3. WHY YOU ARE SWITCHING OFF ARC PROTECTION MCB WHEN
YOU ARE TAKING SHUTDOWN FOR LV BOARD.
4. WHY IT IS NECESSARY TO ISOLATE FIRE FIGHTING WHEN
YOU ARE TAKING SHUTDOWN FOR LV BOARD.
5. HOW YOU GIVE CLEARANCE TO A SPARE FEEDER.
6. HOW TO PUT BREAKER IN SERVICE / TEST POSITION.
7. OPERATION OF ISOLATORS.
8. LOAD TRANSFER IN 11KV DOUBLE BUSBAR SWITCHGEAR -
OPERATION.
9. HOW TO CHECK THE CABLE FAULT / HV TEST OF
TRANSFORMER CABLE.
10. HOW TO DO MAINTENANCE OF TRANSFORMER FEEDER.
11. HOW TO DO MAINT. OF BUSBAR.
12. SINGLE LINE DIAGRAM FOR DBB (DOUBLE BUS BAR)SYSTEM.
13. WHICH TYPE OF ARC PROTECTION DEVICES USED.
14. HOW EARTHING OF SWITCHGEAR SYSTEM TO BE DONE.
15. WHAT ARE OPTIONS USED FOR EARTHING THE SWITCHGEAR.
16. WHAT ARE LOCATIONS ARC PROTECTION RELAY IS FIXED.
17. ZONE OF PROTECTION AND TRIPPING SCHEME OF ARC
PROTECTION RELAY.
18. HIGH SPEED EARTH SWITCH OPERATION WITH DIAGRAM
19. DIFFERENCE IN LOAD BREAK SWITCH, ISOLATOR AND
CIRCUIT BREAKER.
Swgr Page 1 of 4
20. IF BREAKER IS UNDEFINED POSITION, FIRST STEP TO DO.
21. LOAD BREAK SWICTH MAINTENANCE PROCEDURE.
22. WHAT IS DOUBLE THROW ISOLATOR AND SINGLE THROW
ISOLATOR.
23. AFTER TAKING SHUTDOWN OF 11KV FEEDER, IF YOU SEE
5KV BY PHASING STICK IN THE CABLE SIDE, IS IT POSSIBLE TO
CLOSE EARTH SWITCH IN CABLE.
24. FEEDER SHUTDOWN PROCEDURE.
25. WHY TR. FEEDER 132KV SIDE DOES NOT HAVE MW, MVAR
METERS.
26. BACK TO BACK BUSBAR ARRANGEMENT – BBC MAKE –
EXPLAIN.
27. WHAT IS SHUNT REACTOR AND WHERE IT IS USED.
28. WHAT IS FAULT CURRENT. WHAT IS THE LIMITATION.
29. IF WE CLOSE THE FEEDER ON DEAD FAULT, WHAT WILL
HAPPEN
30. IF ISOLATOR IS OPENED ON LOAD, WHAT WILL HAPPEN.
31. WHAT IS CLOSING TIME AND OPENING TIME OF CIRCUIT
BREAKER.
32. HOW YOU WILL GIVE SWITCHGEAR AND PROTECTION
CLEARANCE.
Swgr Page 2 of 4
33. WHAT WILL HAPPEN IF WE SWITCH OFF NEUTRAL CB OF NGR.
34. IN 11KV SWITCHGEAR, WHICH IS OPERATED FIRST: BUS
SECTION or BUS COUPLER.
35. SCHEME FOR CONTROL CIRCUIT OF CB, ISOLATOR.
36. SCHEME OF INTERLOCK FOR ISOLATOR, CIRCUIT BREAKER,
EARTHING SWITCHES.
37. WHAT IS DUTY CYCLE OF BREAKER.
38. WHAT IS TRIP FREE OPERATION IN BREAKER
39. BATTERY CHARGER AND BATTERY - TYPE, PROCEDURE FOR
MAINT.
40. WHAT IS BATTERY CAPACITY TEST – EXPLAIN
41. LIMIT FOR DEWPOINT AND %VOLUME IN SF6 GAS. IF
BELOW, WHAT YOU WILL DO.
42. WHAT IS GRID RESISTANCE VALUE. EARTH PIT
RESISTANCE. IF IT IS HIGH WHAT YOU WILL DO.
43. WHY THERE IS INTERLOCK IN INCOMER WITH BUS SECTION
IN LV BOARD.
44. HOW TO TAKE MAINTENANCE OF 6.6KV NEUTRAL BUSBAR IF
WE TAKE ONE POWER TR. MAINTENANCE.
Swgr Page 3 of 4
45. WHAT IS THE INTERLOCK PROVIDED IN CABLE FEEDER
WHILE EARTHING CABLE WHEN FAR END CB IS NOT OPENED.
46. WHAT ARE CHECKS IN VCB; GCB; MOCB DURING MAINTENANCE
47. WHICH TYPE OF V.T. IS USED IN 132KV GIS SWITCHGEAR
(INDUCTIVE OR CAPACITIVE)
48. WHAT TYPE OF MCB’S ARE USED FOR V.T. SECONDARY
CIRCUIT.
what happens when back feeding supply accidently collapses
with normal supply ??? How??
[that is sometimes in a substation 11kv feeder if their ws
long time permit work, back feeding supply will provide from
nearest substation... if accidently after the permit
work,they charged the feeder without removing back feeding
wat will happen...?]
if transmission voltage expressed as the multipple of form
factor(1.11)........11,33,66,220 etc......then why
madakkathara substation(kerala) voltage is 400kv..not 440.....?
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