Which of this is not representing as operating state of power system

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Examoogle · Accepted Answer

State Estimation

Explanation: In power system security analysis, the operating states are typically classified as Normal, Alert, Emergency, In-extremis, and Restorative. State estimation is a data processing function used to estimate the current network state (voltage magnitudes and angles) based on telemetered measurements, rather than being an 'operating state' of the physical power system itself.

Working Principle: The Power System operating states define the security level based on load demand, constraints, and stability. While 'Optimal Dispatch' and 'Security Dispatch' refer to control actions or modes to maintain system health, and 'Post Contingency' refers to a condition following a failure, State Estimation is the mathematical tool (using Weighted Least Squares or similar) that provides the input data required to assess which state the system is currently in.

Key Formulas: $J(x) = \sum_{i=1}^{m} [z_i - h_i(x)]^2 / \sigma_i^2$ — The Weighted Least Squares objective function used in State Estimation; $P_{loss} = I^2 R$ — Basic parameter minimized during Optimal Dispatch

Key Points: Operating states are transitions of the system stability and constraint satisfaction.; The Five-State model includes Normal, Alert, Emergency, In-extremis, and Restorative.; State Estimation is an observability application, not an operational condition.; Security Dispatch is the process of setting setpoints to ensure security constraints are met.

Advantages: Clarifies distinction between computational tools and system states.; Defines the boundary of Security Assessment functions.

Disadvantages: Often confused because state estimation is required for real-time monitoring of any state.

Applications: Energy Management Systems (EMS); Real-time grid monitoring; Security-Constrained Optimal Power Flow (SCOPF)

Additional Info: Option A (Optimal Dispatch) is an operating mode to minimize cost/loss.. Option B (Post Contingency) is a degraded operating state following a disturbance.. Option C (Security Dispatch) is a dispatch mode ensuring security limits are maintained.. State Estimation is the mathematical 'filter' that processes raw SCADA data.

Answer: D is correct — State Estimation is a software-based analytical tool used to calculate system variables, not a power system operating state itself.

Exam Tip: Remember that State Estimation sits between the data acquisition (SCADA) and the security applications in the EMS hierarchy.

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