211. If the operation of a relay does not involve any change in air gap, then the ratio of rest to pick up is usually
A. 0.306 p.u.
B. 0.33 p.u.
C. 0.318 p.u.
D. 0.328 p.u.

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212. Plug setting of a relay can be altered by varying
A. number of ampere-turns
B. air gap of magnetic path
C. adjustable back up stop
D. none of these

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213. Directional relays respond to the
A. flow of current
B. voltage polarities
C. flow of power
D. all of these

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214. Which of the following is not an instantaneous relay?
A. induction disc type
B. hinged armature type
C. balanced beam type
D. polarized type

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215. Which of the following is an instantaneous relay?
A. thermocouple type
B. induction type
C. permanent magnet moving coil type
D. shaded pole type

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216. Which of the following is a directional relay?
A. mho relay
B. reactance relay
C. impedance relay
D. both (a) and (b) above

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217. Protective relays are devices which detect abnormal conditions in electrical circuits by measuring
A. current during abnormal condition
B. voltage during abnormal condition
C. both A and B simulataneously
D. constantly the electrical quantities which differ during normal and abnormal conditions

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