NETA Protective Relay Applications 2

Question 1

What is the primary function of a distance relay (21) in transmission line protection?

Accepted Answer

Measure impedance to the fault location

Answer

A distance relay measures the impedance from the relay location to the fault, using both voltage and current inputs to determine fault location.

Question 2

Which relay characteristic is best suited for protecting a transformer against internal turn-to-turn faults?

Accepted Answer

Differential relay (87)

Answer

The differential relay (87) compares current entering and leaving the transformer; internal faults cause an imbalance that triggers tripping.

Question 3

In a Mho distance relay, the operating characteristic on an R-X diagram is shaped like a:

Accepted Answer

Circle passing through the origin

Answer

The Mho relay characteristic is a circle on the R-X diagram that passes through the origin, providing inherent directionality.

Question 4

What does the term 'reach' mean in the context of a distance relay?

Accepted Answer

The impedance setting that defines the protected zone boundary

Answer

Reach is the impedance value (in ohms) up to which the relay will operate, defining the boundary of the protection zone.

Question 5

A pilot protection scheme uses communications between line terminals primarily to:

Accepted Answer

Achieve high-speed tripping for faults anywhere on the protected line

Answer

Pilot schemes use communications to allow both terminals to trip simultaneously for internal faults, achieving high-speed protection for the full line length.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

NETA Protective Relay Applications 2