Test: Power Systems - 3 - Electrical Engineering (EE) MCQ

single-phase to earth fault.

phase-to-phase fault.

all the three phases-to-earth fault.

all the three phases short-to earth fault.

any of the above

Single-phase-to earth.

Phase-to-phase.

All the three phases-to earth.

Two phases-to earth.

Alternator.

Transformer.

Overhead lines.

Underground cable

Alternators.

Switchgear.

Transformers.

Underground cable.

neither 1 nor 2

2 alone

1 alone

1 and 2

the number of equations becomes smaller.

the sequence networks do not have mutual couplings.

the results are required in terms of symmetrical components.

None of these

zero.

phasor sum of phase currents.

same as rms value of phase currents.

same as peak value of phase currents.

zero-sequence currents only.

positive-sequence currents only.

negative-and zero-sequence currents.

zero, negative and positive sequence currents.

always zero.

1/3 of negative sequence current.

equal to negative current.

3 times negative sequence current

single-line-to ground fault.

line-to-line ground fault.

double-line-to ground fault.

line-to-line

synchronous generator.

synchronous motor.

static load.

transmission line.

equal to the positive-sequence reactance.

larger than the positive-sequence reactance.

smaller than the positive-sequence reactance.

None of these

L-L fault.

L-G fault.

L-L-G fault.

L-L-L fault.

cheapest type of protection.

inverse time-current characteristic.

no maintenance.

current limiting effect under short-circuit conditions.

all of the above.

open the circuit.

protect the appliance.

protect the line.

prevent excessive currents from flow through the circuit.

SF6

distilled water.

carbon tetra chloride.

transformer oil.

high speed operation.

high rupturing capacity.

no ageing effect.

all of the above.

pre-arcing time.

arcing time.

total operating time.

none of these

short-circuit current.

the combination is newer employed in practice

under all abnormal currents.

low overload currents. 

same as opening time

opening time + arc duration

opening time + arc duration + resistor current duration.

none

circuit breaker operates then the relay.

relay operates, then successively the isolator and the circuit breaker.

relay operates then the circuit breaker.

isolator operates, then successively the relay and the circuit breaker.

thermionic emission of electrons.

field emission of electrons

(a) and (b) both.

  none of the above

carbon.

copper.

silver.

tungsten

single-phase-to ground.

phase-to-phase.

two-phase-to ground.

three-phase to ground