Power Grid Operations & Management Flashcards

Which phenomenon causes power to flow on unscheduled parallel paths through neighboring control areas?

Answer: Loop flow (circulating power)

Loop flow occurs because power follows Kirchhoff's laws and divides among all parallel paths, often flowing through unintended transmission corridors.

What is the function of a phase angle regulator (PAR) on a transmission system?

Answer: Control the magnitude and direction of real power flow by shifting the voltage angle

A PAR introduces a phase angle shift between sending and receiving end voltages to control real power flow on a specific transmission path.

During restoration after a blackout, why must operators carefully match voltage and frequency before closing ties to an energized island?

Answer: To avoid a damaging fault current surge that occurs when two unsynchronized sources are connected

Connecting two asynchronous sources causes a large equalizing current that can damage equipment; synchronization checks ensure voltage magnitude, phase angle, and frequency are matched.

What is the significance of the 'dead band' setting in a turbine governor?

Answer: The speed range within which the governor does not respond, reducing wear from hunting

A governor dead band prevents continuous hunting around the setpoint by ignoring small frequency deviations, balancing responsiveness with mechanical wear.

A system operator needs to increase transmission capacity on an overloaded corridor. Which of the following is a valid operational tool?

Answer: Adjusting generation dispatch to shift flows away from the overloaded line (redispatch)

Redispatching generation re-routes power flows in accordance with physical network laws, relieving the overloaded corridor without removing equipment from service.

Under NERC standards, what must a Balancing Authority do if its ACE cannot be corrected within the specified time limit?

Answer: Notify its Reliability Coordinator and implement corrective actions per the emergency operating plan

NERC BAL standards require timely ACE correction; persistent ACE violations require notification of the Reliability Coordinator and execution of established emergency procedures.

What is 'voltage stability margin' and why do operators monitor it?

Answer: The additional MW load that can be served before the system reaches the nose point of the PV curve and voltage collapses

Voltage stability margin quantifies how much additional load can be absorbed before voltage collapse; monitoring it allows operators to take preventive action before instability occurs.