Grid Reliability Flashcards

What is the primary function of Automatic Generation Control (AGC) in maintaining grid reliability?

Answer: It continuously adjusts generator output to maintain area control error near zero and correct frequency

AGC automatically sends raise/lower signals to participating generators to balance generation with load and maintain the Area Control Error (ACE) near zero, supporting frequency regulation.

During a widespread voltage collapse, which characteristic typically precedes the collapse?

Answer: Voltages decline progressively despite reactive power support, and reactive reserves are exhausted

Voltage collapse is preceded by declining voltages and depletion of reactive power reserves; once reactive reserves are exhausted, voltage can collapse rapidly and uncontrollably.

What does the term 'islanding' refer to in power system operations?

Answer: A grid section operating in isolation from the main interconnection

Islanding occurs when a portion of the power system becomes electrically separated from the main grid and operates independently, which may be intentional (controlled) or unintentional.

Under NERC Standard EOP-006, what is the primary goal of a Transmission Operator during system restoration?

Answer: To restore the system in a manner that re-establishes the transmission network and supports generation pick-up safely

EOP-006 requires TOPs to follow restoration plans that safely re-energize transmission paths and coordinate generation pick-up to restore reliable system operation.

Which scenario best describes an 'N-2 contingency' condition?

Answer: The simultaneous or sequential loss of two bulk electric system elements

N-2 contingency refers to the loss of two system elements (lines, generators, transformers) and is used to evaluate the system's ability to withstand more severe disturbances than the basic N-1 standard.

A system operator sees that the Area Control Error (ACE) is persistently negative. What does this indicate?

Answer: The control area is generating less than its load plus net scheduled interchange, causing it to draw unscheduled power from neighbors

A persistently negative ACE means the area is importing more power than scheduled (under-generating relative to load), placing an unscheduled burden on neighboring areas.

What is the significance of the 'must-run' designation for certain generating units?

Answer: These units must operate to maintain reliability in specific locations regardless of economic dispatch order

Must-run units are committed for reliability reasons (voltage support, local capacity, stability) rather than economics, and they must operate even if they are not the lowest-cost resource.