Switchgear protections

neutral wire

negative of D.

circuit C. positive of

phase dine

transient state of short-circuit current

sub-transient state of short-circuit current

steady state of short-circuit current

after D. C. component has ceased

short-circuits

heavy loads

grounds

all of the above

inversely proportional to the current

inversely proportional to the square of the current

proportional to the current

proportional to square of the current

negative circuit only

positive circuit only

circuits, is inserted in A. negative circuit only B. positive circuit only C. both (A) and (B)

either (A) or (B)

no ageing effect

high speed of operation

fuse, as compared to a rewirable fuse, has A. no ageing effect B. high speed of operation C. high rupturing capacity

all of the above

generators

busbars

transformers

motors E. all of the above

2

4

6

10

100 microsecond

50 millisecond

0.5 sec

0.1 sec

In phase with the arc current

Lagging the arc current by 90°

circuit breaker is always A. In phase with the arc current B. Lagging the arc current by 90° C. Leading the arc current by 90°

None of the above