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Types of Relays in Protection Systems

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Questions and Answers

What is the primary function of relays in protection systems?

To generate power in a electrical circuit

To amplify weak signals

To regulate voltage and current levels

To detect faults and trip directly (correct)

What type of relay is commonly used as an output relay for many solid-state protective relays?

Solenoid relay

Clapper relay

Telephone relay (correct)

Induction cup relay

What is the advantage of high-dropout models of solenoid type relays?

They have a lower dropout value (correct)

They have a higher operating current

They have a higher pickup value

They have multiple contacts

What is the purpose of taps or other means in AC type relays?

To change the pickup value Signup and view all the answers

What happens when the current or voltage drops to the order of 60% of the pickup value in some relays?

The relay drops out Signup and view all the answers

What type of relay is used as a seal-in contact switch in DC applications?

Solenoid relay Signup and view all the answers

What is the percentage of the pickup value at which the fault detectors will reset?

90% Signup and view all the answers

What is the primary function of the moving cup or cylinder in the AC induction cup or induction cylinder unit?

To rotate the contacts and spring to provide reset Signup and view all the answers

What type of fault detectors are recommended in general?

High-dropout type Signup and view all the answers

What happens when the fluxes of coils one and two are in phase?

No rotational torque exists Signup and view all the answers

What is the typical time of operation of the instantaneous overcurrent unit?

16-20 ms Signup and view all the answers