Power Grid Operations & Management Flashcards

What is the role of a Reliability Coordinator (RC) compared to a Balancing Authority (BA)?

Answer: The RC has the widest area view and coordinates reliability across multiple BAs; BAs manage real-time balance within their own footprint

The Reliability Coordinator oversees a larger footprint, identifies wide-area threats, and directs BAs when actions in one area affect reliability elsewhere.

Which condition best describes a 'stable' power system in terms of rotor angle?

Answer: Rotor angles of all generators remain bounded and return to a steady-state following a disturbance

Transient stability requires that generator rotor angles remain bounded and that machines re-synchronize to a new equilibrium after a disturbance.

What does 'load shedding' accomplish during an underfrequency emergency?

Answer: Reduces the generation-load imbalance by removing load, allowing frequency to recover

Automatic underfrequency load shedding (UFLS) removes blocks of load to reduce the imbalance between available generation and demand, arresting frequency decline.

Why is reactive power not transmitted efficiently over long transmission distances?

Answer: Reactive power flow produces large voltage drops and consumes significant system capacity without delivering useful work

Reactive power flow causes I²X losses and significant voltage gradients, making remote reactive support inefficient; reactive compensation should be placed close to the load.

A dispatcher receives a NERC Alert for a geomagnetic disturbance (GMD). What operational concern is most relevant?

Answer: Geomagnetically induced currents (GIC) saturating transformer cores, causing harmonics and reactive absorption

GMD drives quasi-DC geomagnetically induced currents into transformer neutrals, saturating cores, increasing reactive demand, and potentially causing thermal damage.

What is meant by the 'loadability limit' of a transmission line?

Answer: The maximum power that can be transferred over the line while maintaining voltage stability and staying within all thermal and stability limits

Loadability combines thermal, voltage, and stability constraints to define the practical maximum power transfer for a given line and system configuration.

During a widespread disturbance, a dispatcher notices islanded subsystems operating at different frequencies. What does this indicate?

Answer: Each island has a unique generation-load imbalance; overloaded islands have low frequency and over-generating islands have high frequency

When a system splits into islands, each island's frequency reflects its own generation-load balance; divergent frequencies confirm the separation and indicate which islands need remediation.