SOPD Protection Systems & Relay Operations 3

Question 1

Which of the following relay characteristics is best suited for protecting a high-voltage transmission line where load encroachment may be a concern?

Accepted Answer

Quadrilateral characteristic

Answer

Mho (circular) characteristic

Answer

Reactance characteristic

Answer

Inverse-time overcurrent characteristic

Question 2

What is the purpose of a 'zone 3' setting in a step-distance protection scheme?

Accepted Answer

To provide remote backup protection for adjacent lines beyond zone 2

Answer

To provide instantaneous, primary protection for the local line section

Answer

To detect power swings and block tripping during stable swings

Answer

To protect the local bus from phase-to-ground faults

Question 3

A 'Permissive Overreaching Transfer Trip' (POTT) pilot scheme sends a permissive signal when:

Accepted Answer

The local relay detects a fault within its overreaching zone (zone 2 or beyond)

Answer

The local relay detects a fault within zone 1 only

Answer

The remote terminal breaker opens and current drops to zero

Answer

A manually initiated transfer trip command is sent by the operator

Question 4

When a system operator is required to take protective relay equipment out of service for maintenance, which of the following actions is typically required?

Accepted Answer

Obtain approval and implement compensating measures per the applicable protection maintenance standard

Answer

Permanently disable the relay until maintenance is complete

Answer

Transfer the relay's function to the EMS alarm system

Answer

Increase the loading on the protected element to test for any faults during the outage

Question 5

What phenomenon can cause a distance relay to 'underreach' (fail to detect a fault within its set zone)?

Accepted Answer

High fault resistance in the fault path

Answer

Power factor leading conditions on the line

Answer

A shunt reactor connected at the remote bus

Answer

Transformer tap position being at minimum

Question 6

In the context of protection system batteries, what does the NERC PRC-005 standard require regarding battery testing?

Accepted Answer

Periodic performance testing must be performed to verify that the battery can supply the required load for a specified duration

Answer

Batteries must be replaced every 12 months regardless of test results

Answer

Batteries must maintain a float voltage of exactly 125 VDC at all times

Answer

Battery testing is only required following a system disturbance or relay operation

Question 7

A line protection relay that uses 'directional' elements will only operate when fault current flows in which direction?

Accepted Answer

In the direction from the bus toward the protected line (into the zone)

Answer

In either direction, since direction does not affect the overcurrent pickup

Answer

Away from the protected line and toward the source

Answer

In a direction determined by the highest load current reading