PHEP27 Protective Relays

Question 1

When CT’s are used with protective relays the direction of current flow in the transformer windings (polarity marks):

Answer 1

Must be carefully observed for relay types which depend on the interaction of two currents for their action.

Question 2

Differential current relays are designed and installed to protect against:

Answer 2

Internal faults.

Question 3

The relay-time setting is adjusted by means of:

Answer 3

Time-index lever.

Question 4

Protective relays may be classified according to their: construction, type of movement, and contacts.

They are not classified:

Answer 4

According to the manner in which they are connected in the circuit.

Question 5

Polyphase rotating equipment may be protected against single phase operation by using a:

Answer 5

Phase-balance relay.

Question 6

Sudden pressure relays are for the protection of:

Answer 6

Transformers.

Question 7

An induction-disc time overcurrent relay:

Answer 7

Is adjusted separately for the degree of overcurrent at which it operates and also for the amount of time delay.

Question 8

The term zones of protection applies most nearly to the isolation of faulted equipment:

Answer 8

Throughout the entire power system.

Question 9

Protective relays, in general, must be able to:

Answer 9

All of these:

Remove or isolate the local area of a fault from the rest of the system.

Locate faults and trips only those circuit breakers directly connected to the faulty equipment.

Differentiate between permissible operating conditions and abnormal or fault conditions

Question 10

A relay which would normally respond to changes in circuit admittance, impedance, and reactance is called a:

Answer 10

Distance relay.

Question 11

All of the following statements concerning the schematic shown in Fig. 28 are true except for:

Answer 11

The position of the pallet switches indicates that the OCB is in a closed position.

Question 12

All of the following statements concerning the schematic shown in Fig. 28 are true:

Answer 12

All Y contacts are closed and all X contacts are open.

Relay device #51 is a two element relay protecting a three-phase delta connected unit from overload or fault current.

Relay device #46 is giving protection against single phasing.

Question 13

Fault power always:

Answer 13

Flows toward the fault.

Question 14

A device which contacts in one circuit are operated by a change in conditions in the same or another circuit is called a:

Answer 14

Relay.

Question 15

All protective relaying may be classified according to the:

Answer 15

Function they perform.