Bad data detection considering the accuracy of instrument transformers

The main task of the state estimator in power systems is the provision of the power system state accurately. In order to achieve this, the measurement set has to be validated by identifying erroneous measurements. This is usually achieved by using either the Chi-square or the Largest Normalized Residual test. In both tests, the estimated states that are provided by the state estimator and the measurement variances included in the measurement error covariance matrix are used for detecting the erroneous measurements. The measurement error covariance matrix is usually formulated using the accuracy of the measurement device only, ignoring the quality of other elements in the measurement chain such as the instrument transformers. In this paper, the effect of instrument transformer measurement quality on the bad data detection algorithm is investigated. Further, simulation results based on the IEEE 118-bus system are provided.