Discrimination between main and back up protection is provided by the use of relays which are

The inverse definite mean time relays are used for over current and earth fault protection of transformer against

A

heavy loads

B

internal short-circuits

C

external short-circuits

D

all of the above

The single phasing relays are used for the protection of

A

single phase motors only

B

two phase motors only

C

two single phase motors running in parallel

D

three phase motors

Switches and relays should be shown in this position with no operating force or applied energy:

A

Normal

B

Closed

C

Offset

D

Application

Who built the world's first electronic calculator using telephone relays, light bulbs and batteries?

A

Claude Shannon

B

Konard Zuse

C

George Stibitz

D

Howard H. Aliken

E

None of the above

Which of the following relays is used on long transmission lines?

A

Impedance relay

B

Mho's relay

C

Reactance relay

D

None of the above

The phase lag produced by transportation relays

A

Is independent of frequency

B

Is inversely proportional to frequency

C

Increases linearly with frequency

D

Decreases linearly with frequency

Thermal overload relays are used to protect the motor against over current due to

A

short-circuits

B

heavy loads

C

grounds

D

all of the above

Overload relays are of type.

A

induction

B

solid state

C

thermal

D

electromagnetic

E

all above

Directional relays are based on flow of

A

power

B

current

C

voltage wave

D

all of the above

Relays can be designed to respond to changes in

A

resistance, reactance or impedance

B

voltage and current

C

light intensity

D

temperature

E

all above

Discrimination between main and back up protection is provided by the use of relays which are

Related Questions