SOPD Voltage Control & System Reliability 3

Question 1

What is the significance of the 'nose point' on a P-V curve?

Accepted Answer

It represents the maximum power transfer point beyond which voltage collapse is imminent

Answer

The nose point is the critical maximum loadability limit on a P-V curve; operating beyond it causes voltage collapse.

Question 2

A transformer's load tap changer (LTC) is set to automatic mode during a system emergency with low voltage. Why might operators place the LTC in manual mode?

Accepted Answer

To prevent LTC operation from masking low voltage conditions and depleting reactive reserves further

Answer

Automatic LTC action during low voltage can mask the true voltage problem and increase reactive demand, worsening reactive reserve depletion.

Question 3

Which NERC Reliability Standard specifically addresses Transmission Operator requirements for maintaining voltage profiles?

Accepted Answer

VAR-001

Answer

VAR-001 (Voltage and Reactive Control) establishes requirements for Transmission Operators to maintain voltage and reactive control within defined limits.

Question 4

A shunt reactor is connected to a 500 kV bus during light load conditions. What is its primary function?

Accepted Answer

To absorb reactive power and prevent overvoltage due to line charging

Answer

Shunt reactors absorb reactive power (consume VARs), counteracting the capacitive charging of lightly loaded long transmission lines that would otherwise cause overvoltage.

Question 5

During a post-contingency analysis, an N-1 contingency is found to cause a bus voltage to drop to 0.91 pu. Under NERC TPL standards, this result indicates:

Accepted Answer

A possible violation requiring evaluation against applicable voltage limits and corrective action plans

Answer

A post-contingency voltage of 0.91 pu may violate planning or operating voltage limits, requiring evaluation and a corrective action plan per NERC TPL standards.

(SOPD) System Operator/Power Dispatching Practice Test

(SOPD) System Operator/Power Dispatching Practice Test

SOPD Voltage Control & System Reliability 3