Critical measuring units for state estimation

Power system state estimation (SE) performance is very much influenced by the availability of redundant, varied, well-located measurements. Insufficient supplies of qualified measurements can compromise network observability, making the SE process incompetent to detect/identify spurious data. Individual or group of measurements whose unavailability renders unobservability are known as critical for the SE purpose. One can define a measuring unit as critical, if the set of measurements it provides is essential to the network observability. This paper focuses on the identification of critical measuring units, which is achieved by processing selected measurements in the estimation residual covariance matrix. The proposed identification method is straightforward and reliable, being easily implemented into any existing state estimator. With the IEEE 30-bus test system, illustrative examples are presented to show how the proposed approach can be used to evaluate measurement plans.