Switchgear and Protection Part-3

Switchgear and Protection

1. If the restriking voltage rises more rapidly than the dielectric strength, gap space breaks down and arc strikes again and persist. This is_________.

a. Slepians Theory

b. Energy Balance Theory

c. Cassie's Theory

d. Cascade Theory

2. Merz price circulating-current system does not protect the alternator______.

a. L-G fault

b. phase-to - phase

c. turn-to-turn fault on the same phase winding of the stator

d. L-L-G fault

3. Percentage (%) bias in the differential relay is_________.

a. Bias Current

b. Differential Current

c. Current due to spring constant

d. ratio of number of turns of bias coil to the number of turns of operating coil

4. The burden of a protective relay is the power________.

a. Required to operate the circuit breaker

b. Absorbed by the relay trip circuit

c. Developed by the relay circuit

d. Absorbed by the transmission line

5. Current setting of relay 1 is 100% and relay 2 is 125%. For both the relays given CT ratio- 400/5. Fault current- 2000A. Determine the PSM of both the relays.

a. 5.8, 4.5

b. 10, 8

c. 6, 8

d. 5, 4

6. At ZPF lag, this directional relay connection is not prefferred_____.

a. Relay Angle = 90 degrees with maximum torque angle = 45 degrees

b. Relay Angle = 30 degrees with maximum torque angle = 0 degrees

c. Relay Angle = 30 degrees with maximum torque angle = 45 degrees

d. Relay Angle = 90 degrees with maximum torque angle = 0 degrees

7. A Buchholz relay is used for_______.

a. Protection of a transformer against external faults.

b. Protection of induction motors.

c. Protection of a transformer against both internal and external faults

d. Protection of a transformer against internal faults.

8. Which of the following parameters can be neglected for a short line ?

a. Capacitance

b. Reactance

c. Resistance

d. Inductance

9. Admittance relay is_____ a relay.

a. Over Current Directional Relay

b. Directional Distance Relay

c. Non-directional Distance Relay

d. Differential Relay

10. Compute the average rate of rise of restriking voltage, where  source, v(t) = 10000 cos314t volts, L= 1mH, C= 500pF.

a. 6 kV/microseconds

b. 9 kV/microseconds

c. 11 kV/microseconds

d. 15 kV/microseconds

11. MHO relay is inherently _______ type.

a. unidirectional

b. non-directional

c. directional

d. overcurrent

12. The following statement is associated with the Buchholz relay is not true________.

a. It is a gas actuated device

b. It is a current operative device

c. It is placed between the transformer tank and the conservator

d. It causes alarm for minor fault and tripping for major fault

13. Directional restraint overcurrent relay is employed to measure____.

a. Reactance

b. Impedance

c. Admittance

d. Overcurrent

14. If the relay torque is given by, T= k₁ I² - k₂ V² - k₂ is the spring constant, the relay is called as_____.

a. Directional Restrained Overcurrent Relay

b. Voltage Restrained Directional Relay

c. Voltage Restrained Overcurrent Relay

d. Directional Restrained Overvoltage Relay

15. If the excitation fails, synchronous generator runs at a super-synchronous speed and______.

a. Supplies reactive power to the power system

b. Reactive Power has no role to play

c. Reactive Power is zero

d. draws reactive power from the power system

16. The most commonly used scheme for busbar protection is_______.

a. Differential protection

b. Distance Protection

c. Time-graded overcurrent protection

d. Translay Scheme

17. R, L, C, transistors, analog ICs comparators are used in ________.

a. Thermal Relay

b. Static Relay

c. Electromagnetic Relay

d. Numerical Relay

18. The economical protection preferred for the magnetic inrush currents in inexpensive transformers is_______.

a. Mho Relay

b. IDMT relay with delay of 5 to 6 cycles

c. Reactance Relay

d. 2nd Harmonic Restraint Relay

19. High resistance interruption method is not suitable for_______.

a. Miniature AC Breaker

b. HV AC and DC Breakers

c. Low voltage AC Breakers

d. Medium Voltage AC breakers

20. Speed of response of this relay is the fastest_______.

a. Thermal Relay

b. Static Relay

c. Electromagnetic Relay

d. Numerical Relay

21. The thermal circuit breaker has_______.

a. Delayed trip action

b. Instantaneous trip action

c. Instantaneous short action

d. Any of the above

22. Circuit breakers are essentially_______.

a. Current carrying contacts called electrodes

b. Arc extinguishers

c. Circuits to break the system

d. Transformers to isolate the two systems

23. The stability of arc in vacuum depends on _________.

a. The contact material only.

b. The circuit parameters only.

c. The contact materials and its vapour pressure.

d. Both (b) and (c)

e. None of these