Question 1

Which is the main relay for protecting up to 90% of the transmission line-length in the forward direction?

Accepted Answer

A)  Directional over current relay
B)  Mho relay
C)  Carrier current protective relay
D)  Impedance relay B

Question 2

The relay used for feeder protection is

Accepted Answer

A)  Under voltage relay
B)  Translay relay
C)  Thermal relay
D)  Buchholz relay B

Question 3

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should

Accepted Answer

A)  Have low contact resistance
B)  Be clean and smooth
C)  Be of sufficient size and proper shape
D)  Have all above properties D

Question 4

To prevent mal operation of differentially connected relay while energising a transformer, the relay restraining coil is biased with

Accepted Answer

A)  Second harmonic current
B)  Third harmonic current
C)  Fifth harmonic current
D)  Seventh harmonic current

Question 5

The single phasing relays are used for the protection of

Accepted Answer

A)  Single phase motors only
B)  Two phase motors only
C)  Two single phase motor running in parallel
D)  Three phase motors

Question 6

In the case of transmission line protection, over current relay is used

Accepted Answer

A)  Only up to 110 KV
B)  Only up to 220 KV
C)  Only up to 50 KV
D)  Only up to 1100 KV

Question 7

To protect most of the electrical equipment handling low power, the types of relays used are

Accepted Answer

A)  Thermocouple
B)  Electronic and bimetallic
C)  Both A and B
D)  None of the above

Question 8

........ Relays is preferred for phase fault on short transmission line

Accepted Answer

A)  Induction type
B)  Reactance
C)  Impedance
D)  None of the above

Question 9

Zero sequence current is used for relaying purpose only in the case of

Accepted Answer

A)  Phase over current really
B)  Phase impedance relay
C)  Ground over current relay
D)  Ground impedance relay

Question 10

Admittance relay

Accepted Answer

A)  Nondirectional relay
B)  Directional relay
C)  Differential relay
D)  None of the above

Question 11

Where severe synchronising swing occur, the relay employed is

Accepted Answer

A)  Impedance relay
B)  Mho relay
C)  Reactance relay
D)  Induction relay

Question 12

Interruption of large currents by relay requires

Accepted Answer

A)  Arc suppressing blow out coils
B)  Wide separation of the open contacts
C)  High speed opening of contacts
D)  All of the above

Question 13

For the protection of lines against faults involving variable fault resistance, the preferred relaying scheme is a

Accepted Answer

A)  Plain impedance relay
B)  Directional over-current relay
C)  Mho relay
D)  Reactance relay

Question 14

The inverse definite mean time relays are used for over current and earth fault protection of transformer against

Accepted Answer

A)  Heavy loads
B)  Internal short circuits
C)  External short circuits
D)  All of the above

Question 15

............. Relays are used for phase faults on long line

Accepted Answer

A)  Impedance
B)  Reactance
C)  Either of the above
D)  None of the above

Question 16

Relays can be designed to respond to changes in

Accepted Answer

A)  Resistance, reactance or impedance
B)  Voltage and current
C)  Light intensity
D)  All of the above

Question 17

DC shunt relays are made of

Accepted Answer

A)  Few turns of thin wire
B)  Few turns of thick wire
C)  Many turns of thin wire
D)  Many turns of thick wire

Question 18

Which one of the following relay has the capability of anticipating the possible major fault in a transformer ?

Accepted Answer

A)  Over-current relay
B)  Differential relay
C)  Buchholz relay
D)  Over fluxing relay

Question 19

Which relay is used to detect and protect internal fault in a transformer ?

Accepted Answer

A)  Buchholz relay
B)  Directional relay
C)  Thermal relay
D)  Distance relay

Question 20

Directional over current relays have two exciting coils connected across

Accepted Answer

A)  CT secondaries of two different phases
B)  VT secondaries of two different phases
C)  CT and VT secondaries of same phases
D)  CT and VT secondaries of two different phases

Exam 11: Relaying Schemes and Techniques for Electrical Equipment Protection