Secure dispatch is the state of power system where

Question

Examoogle · Accepted Answer

Contingency outage is not present

Explanation: Secure dispatch refers to the operational state of a power system where all components are within their thermal and stability limits, and no contingency outages are currently affecting the system's performance. It ensures that the power system remains in a 'Normal' or 'Alert' state, capable of maintaining supply even if a single component fails.

Working Principle: The system monitors bus voltages and line flows using a State Estimator. It verifies the N-1 security criterion, which mandates that the system remains stable even if one major component (generator or transmission line) undergoes an unplanned outage. Secure dispatch optimizes generation schedules such that $P_{gen} = P_{load} + P_{loss}$ while satisfying inequality constraints like $|S_{line}| \le S_{max}$ and $V_{min} \le |V| \le V_{max}$.

Key Formulas: $N-1 	ext{ Criterion} \implies 	ext{System remains stable under any single contingency outage}$; $\sum P_{gen} = \sum P_{load} + P_{losses}$

Key Points: Security is defined as the ability of the system to withstand a sudden disturbance.; Secure dispatch implies the absence of current emergency conditions.; Power system security is categorized into Normal, Alert, Emergency, and Restoration states.; Contingency analysis is performed to ensure the system is 'Secure'.

Advantages: Minimizes risk of cascading failures.; Ensures continuous and reliable power supply to consumers.

Disadvantages: Increases operational costs due to reserve requirements.; Requires complex real-time computational monitoring.

Applications: Energy Management Systems (EMS) in Load Dispatch Centers.; Real-time grid stability control.

Additional Info: The 'N-1' criteria implies that for a secure state, the loss of any single major element should not cause a violation of system limits.. Option A is incorrect because if a contingency outage were present, the system would typically be in an 'Emergency' or 'Alert' state, not a 'Secure' state.

Answer: B is correct — Secure dispatch is achieved when the system operates within limits with no ongoing contingency outages.

Exam Tip: Always remember the difference between 'Reliability' (long-term adequacy) and 'Security' (short-term operational state).

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