Redundancy of state estimation is

Question

Examoogle · Accepted Answer

1.5 to 2.8

Explanation: Redundancy of state estimation in power systems is defined as the ratio of the number of available measurements to the number of state variables. A redundancy level between 1.5 and 2.8 is typically maintained in modern Supervisory Control and Data Acquisition (SCADA) systems to ensure observability and detect bad data.

Working Principle: State estimation relies on processing telemetered data (voltage magnitudes, real/reactive power flows, and bus injections) to estimate the system state (voltage magnitudes and angles). If the ratio of measurements (m) to states (n) is 1, the system is just observable. A ratio greater than 1 provides degrees of freedom to filter measurement noise and identify outliers through statistical tests like the Chi-square ($chi^2$) test.

Key Formulas: $\eta = \frac{m}{n}$ — where $m$ is the number of measurements and $n$ is the number of states

Key Points: Redundancy improves the reliability of the state estimation process.; Higher redundancy allows for better bad data detection and identification.; Too high redundancy increases telemetry traffic and computational cost.; If $\eta

Advantages: Enhanced filtering of random Gaussian measurement noise.; Capability to identify and reject bad telemetry data.

Disadvantages: Increased bandwidth requirement for communication links.; Higher computational overhead for real-time processing.

Applications: Energy Management Systems (EMS).; Smart grid monitoring and control.; Real-time contingency analysis.

Additional Info: A redundancy of exactly 1 implies a perfectly determined system where no error checking is possible.. Values exceeding 3 are generally considered economically inefficient for standard distribution networks.

Answer: C is correct — the typical redundancy of state estimation in electrical power systems is maintained between 1.5 and 2.8 to ensure optimal performance of the state estimator.

Exam Tip: Remember that redundancy is essentially a measure of 'over-determined' systems; in competitive exams, prioritize the 1.5-2.8 range for practical utility questions.

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