267. Minimum oil circuit breaker has less volume of oil because
A. there is insulation between contacts.
B. the oil between the breaker contacts has greater strength.
C. solid insulation is providedfor insulating the contacts from earth.
D. none of these
268. Carrier current protection scheme is normally used for
A. HV transmission lines only.
B. HV cables only.
C. HV transmission and cables.
D. none of these
269. To limit current chopping in vacuum circuit breakers, the contact material used has
A. high vapour pressure and low conductivity properties.
B. high vapour pressure and high conductivity properties.
C. low vapour pressure and high conductivity properties.
D. low vapour pressure and low conductivity properties.
270. A fault is more severe from the view point of RRRV if it is a
A. short line fault.
B. medium length line fault.
C. long line fault.
D. none of these
271. Positive, negative and zero sequence impedances of a solidly grounded system under steady state condition always follow the relations
A. Z4 > Z2 > Zo
B. Z4 < Z2 < Zo
C. Zo
272. Phase comparators in case of static relays and electro-mechanical relays normally are
A. sine and cosine comparators respectively.
B. cosine and sine comparators respectively.
C. both are cosine comparators.
D. both are sine comparators.
273. For reducing tower footing resistance it is better to use
A. chemical and ground rods only.
B. chemical an counterpoise only.
C. ground rod and counterpoise only.
D. chemical, ground rods and counterpoise.
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