Detection of Topology Errors by State Estimation

In modern energy management systems (EMS), there are two types of measurement data collected by the SCADA (supervisory control and data acquisition) system, namely, status data of breakers and switches, and analog data of real and reactive power flows, injections, and bus voltages. The status data are used to determine real-time topology of the network. The analog data are used to determine line and transformer loading and voltage profile. These data are noisy due to measurement errors, communication noise, missing data, etc. In addition to simple checking of the analog data locally, in most modern EMS, state estimation is used to process these data globally to correct errors in the raw analog measurement data. In this paper, the use of global information in state estimation to correct errors in the direct measurements of the status data is proposed and conditions for detectability of errors are analyzed. The telemetered data of breaker and switch status are processed in the EMS computer to determine the present network topology of the system, and this function is called network topology processor. Errors in status data will show up as errors in the network topology. Sasson et al and Dy Liacco et al used a tree search algorithm for the network topology processor. The method is widely used in practice. Bonanomi et al proposed a sequential search method through the network graph. Recently Lugtu et al suggested the approach of using state estimation results for topology error detection.