MRT & PROTECTION

QUESTION PAPER 

Note: Answer All Questions

SECTION – A

1) What is the full load current of a 3-ph, 17.32MW, 0.8PF, 100 KV generator [ ]a) 216.5 A b) 125A c)100A d) 250A

2) What is the protection provided for both Generator and Transformer Combined [ ]a) O/C Relay b) E/F Relay c) Distance Relay d) Overall Differential Relay

3) Protection for 400KV & 200 KV Lines [ ]

a) O/C Relays b) O/C & E/F Relaysc) One Distance Relay d) Main –I & Main – II distance Relay.

4) Protection for 33KV or 11 KV Lines [ ]a) Distance Relay b)Main –1,Main-II Distance Relay

c) Directional O/C & E/F Relay d) Non – Directional O/C& E/F Relay

5) What is the purpose of Earthing in 132KV and above systems [ ]

a) For Feeding Loads b) Lightning Protection

c) For the operation of relays d) For opening the breaker 

6) What is the approximate value of combined Earth Resistance of [ ]

EHV Sub – Station (Ohms)

a) 1 b) 2 c) 3 d) 5

7) If earth resistance is more fault current is [ ]

a) More b) Less c) High d) Moderate

8) How lightning will form in the clods [ ]

a) By Air b) By Rubbing of clouds c) Ionisation d) Chemical Reaction

9) What is the lighting protection to be provided for the Transformers [ ]

a) CTs b)PTs c) CVTs d) Las

10) What is the lightning protection for Multi – storeyed buildings [ ]

a) Earth Roads b) Shielded Ground Wiresc) Ground Wires d) Lightning Mast ( Pole)

11) No. of CT secondary cores in 11KV & 33KV Line CTS [ ]a) 1 b) 2 c) 3 d) 4

12) No. of CT Secondary Cores in 132 KV Line CTS [ ]

a) 1 b) 2 c) 3 d) 4

13) No. of CT Secondary Cores in 220KV & 400KV Transformers CTs [ ]

a) 2 b) 3 c) 4 d) 5

14) For transformer differential protection of 16 MVA, 132 / 33 KV Transformers; [ ]

[ ] the HV & LT CT Ratio.a) 100/1A & 400/1A b) 100/1 A & 300/1 A

c) 100/0.5775A/400/0.5776A d) 70/1A & 280/1 A

15) What is the full load current on 220KV side of 100 MVA 220/132KVTransformers [ ]

a) 220A b) 440A c) 262A d) 362A

a) 220A b) 440A c) 262A d) 362A

16) How to connect over flux relay on 100 MVA 220/132 KV Transformers [ ]

a) From CTs b) From CVTs

c) From PTs d) From Transformers bushing

 

17) How many mercury floats are available in Buchholzrelay [ ]

a) 1 b) 2 c) 3 d) 4

18) What is provided in the transformers breather [ ]

a) mercury b) Silieagel c) Oil & Silicagel d) Nothing

19) Purpose of the conservator tank in a Transformer [ ]

a) To release air b) to take air c) both d) Nothing

20) 100MVA, 220/132KV Transformer, No. of windings in A.P Power system [ ]

a) One Winding b) Two windings c) Auto Transformer d) Three Windings

21) 220/132KV 100 MVA Transformer HV side protection [ ]

a) Non Directional O/L & E/L b) Directional O/L & E/L

c) Non Directional O/L & Directional E/L d) Directional O/L & Non Directional E/L

22) 10/16 MVA 132/33 KV Transformer 33KVLV side protection [ ]

a) Non Directional O/L & E/L b) Directional O/L & E/Lc) Non Directional O/L & Directional E/L d) Directional O/L & Non Directional E/L

23) The distance between two electrodes should not be greater than ……. the length

of electrodes [ ]a) Double b) thrice

c) Same d) 1.5

24) Bus – Bar Protection will be provided on [ ]

a) 132 KV Bus b) 220 KV Bus c) 11KV Bus d) 33 KV Bus

25) It Bus – Bar Protection is not provided Line Distance Protection [ ]

a) Will see the bus – faults b) Will not see the bus faults

c) Will see with instantaneous time d) Will see with time delay

26) If two 220 KV Buses are there. Bus – Bar Protection Zones [ ]

a) 1 b) 2 c) 3 d) 4

27) Purpose of LBB Relays [ ]

a) For line faults b) For bus faults

c) For un cleared Line faults d) For un cleared bus Faults

28) Electro magnetic Relays require D.C Supply . for [ ]

a) Flagging b) Flagging and Trippingc) For Tripping d) Auxiliary DC Supply

29) Why DC/DC Converters in distance relays fail [ ]

a) high Humidity b) High Ambient Temperaturec) High DC Voltage d) Improper filters in the charger  

30) Unused CT secondary core, should be [ ]a) Left Opened b) Should be shorted

c) Core to be removed d) As it is

31) Select the location of installing capacitor bank, which will reduce the electricity distribution

losses to the maximum extent [ ]

a) Main sub-station bus bars b) motor terminals

c) motor control center d) distribution board bus bars

32) The nearest kVAr compensation required for improving the power factor of a 100 kW loadfrom 0.8 lag to unity power factor is [ ]

a) 50 kVAr b) 75 kVAr c) 100 kVAr d) none of the above

 

33) If voltage is reduced from 230 V to 200 V for a fluorescent tube light,

it will result in [ ]

a) reduced power consumption b) increased power consumptionc) increased light levels d) no change in power consumption and light levels

34) Which of the following is not likely to create harmonics in an electrical system [ ]

a) Soft starters b) variable frequency drives c) UPS d) induction motors

35) Power factor is the ratio of [ ]

a) kW/ (kW2+kVAr 2)1/2 b) (kW2+kVAr 2)1/2/kW

c) kVAr/kW d) kVAr/ (kW2+kVAr 2)1/2 

36) The major source of electrical power generation in India is [ ]

a) Thermal b) Hydel c) Nuclear d) Wind

37) The unit of maximum demand is [ ]a) KVA b) KWH c) KVAH d) KVARH

38) Total T&D losses of A.P.Power system [ ]a) 20.6 b) 19.6 c) 18.6 d) 17.6

39) Battery rating in EHV Sub Stations [ ]a) 110 V b) 200 V c) 100 V d) 220 V

40) The operating time of distance relay in Zone-I [ ]a) 0.3sec b) 0.6 sec c)instant d) 1.0 sec

41) If the reactive power drawn by a particular load is zero, [ ]

it means the load is operating at

a) lagging power factor b) leading power factor c) unity power factor d) none of the above

42) In electricity distribution, if the voltage is raised from 11 kV to22 kV for the same loading conditions, the voltage drop in electrical system

would be lower by a factor of [ ]

a) 1/2 b) 1/4 c) 1/16 d) none of the above

43) The temperature rise in a earth joints should not exceed …………. Degree centigrade,

if it is a welded joint under fault conditions. [ ]

a) 650 b) 450 c) 250 c)1050

44) While boosting, the Maximum permissible temperature rise in a battery is ….. ,

a) 600 C   b)450 C c) 650 C d) 150 C [ ]

45) Carrier communication tripping is used in [ ]

a) below 132KV b)132KV &220KV system c) 400KV & above system

d) none of the above

SECTION- B

FILL IN THE BLANKS

Note: Answer All Question s 15 X 2 marks each = 30 MARKS

 

1) Purpose of each core in 2 core CT ……………….

2) CVTs are used for …………………………………………………………..

3) Types of Circuit breakers……………………………………………………

4) The purpose of tertiary winding of 315MVA, 400KV/220KV/33KV, 3-Ph power transformer 

is ……………………………………………

5) The total movement of controlling rod in 400KV SF6 circuit breaker is …………………….

6) The purpose of the wave trap in substation ……………………..

7) Generally, the secondary ratings of current transformer is………………

8) SCADA means ………………………………………………………….

9) The constant parameters in GRID ………………..

10) The purpose of RVT in Capacitor banks connection …………………..

11) ……………………………………… are provided as protective devices from lighting stokes in

400KV mamidipalli substation.

12) The total losses of 100 kVA transformer for an average loading of 40% is about …………..

(Assume no load and full load losses as 1.70 kW and 10 kW respectively.)

13) The advantage of high voltage transmission system is ………………………………………

and Maximum transmission voltage in India is …………..

14) Battery earthing should not be connected to earth grid because ……………….……………..

15) Continuous current and rupturing ( Breaking) current for 400 KV Breaker……………….

SECTION – C

Note: Answer all Questions 5 X 5 Marks =25 Marks

1) Draw single line diagram of ONE&HALF Breaker system.2) Draw the equivalent electrical circuit of Surge arrestor/ Lighting arrestor and which

material is used in surge arrestor.

3) Draw the single line diagram of railway traction protection system.4) Draw the basic connection diagram of a protection relay and healthy trip circuit.

5) What are the types of relays used for 220/132KV , 100MVA power transformer as per the

norms of APTRansco.