Answer / d.rajagopal

If Lt side is connected it will be possible ARC When tap
Changing, becs Lt side is High Current , So Ht side
connected This is low current

Answer / binay agrawal

in hv side, current will be less; so if we vary the
rheostate, than thetre is less arcing with respect to lv
side, so we always put the tap changer in hv side.

Answer / jay

there are many appx reasons
1. ht is placed outer side of transformer.
2. if tappings are on lv side the number of turns will be
less so if we want to regulate o/p voltage it will vary
with a large difference while if we use tap at high voltage
it will have more number of turns so we were be able to
regulate voltage even in small difference.
3. its current rating is low.

Answer / swayanjit ray

generally tappings are provided on the HV side because on
the HV side of the transformer less current is flowing so
that whenever we change from one tapping to another less arc
will created as compared to LV side. again we can achieve
the better voltage control by providing tapping on the HV side.

Answer / sujeet kumar

1. In HV side current is less so there is less sparking
2. ON the transformer core first we placed LV winding and
above it we place HV winding. Hence it is practically very
difficult to tap from LV winding.

Answer / sujata jha

If we provide tappings on hv side the current utilisation
will be less . so that ohmic and core losses will be
minimised.we can distribute the voltage to various premises
efficiently. power factor also improved.regulation becomes
better....

Answer / jeet

generally tappings are provided on the HV side because on
the HV side of the transformer less current is flowing so
that whenever we change from one tapping to another less arc
will created as compared to LV side.Also due to less current better insulation can be provided.

Answer / lion heart

it is very simple
AS LV winding is placed near the core so as to minimize
hitting effect that will cause if in case HV winding is
placed near the core
and due to such a construction Hv winding is always remains
outside overlapping LV winding, so tapping can be easily
applied to HV winding , while in case LV winding it will be
very difficult to give tappings on it
thank you

Answer / kornelius vattie

HV side of a transformer carries low current in comparison to the LV side of the same transformer. This low current promote little arcs during switching, limits the size of cables to be used, therefore it is also very economical to do tappings here. NB- the higher the Volts, the low the Amps.

Answer / sumit sen

number of turns is more in ht side and also current is less

which type of insulation are used on 132kv transmission line

4 Answers  

In radial network the source is fed from 1 end both ends at central

0 Answers  

What is meant by a stray loss of a induction motor??? What is the equation to find it

0 Answers  

why the transformer ratings in kva

8 Answers   NTPC,

What is differnce b/w tie breaker and bus coupler?

1 Answers  

can we start slipring motor on star delta like we start induction motor ? if yes where will we connect ?

0 Answers   NovaTech,

What is the full form of GSL wire

8 Answers   Bhel, GSL,

how to convert lv line to hv line and viseversa, any losses will occur during this process

0 Answers   Jindal,

Why transformer, generator, ups rating kva?

2 Answers  

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

2 Answers   KSEB, Siemens,

What is the role of power pack in substation protection system?

0 Answers   Facor,

I am getting above 60 V as open delta voltage against single phase unit ICT at tertiary delta formed and ICT getting trippped on NDR. ICT tested and found in order. PTs provided on tertiary are tested and in order. what may be the reason?

0 Answers