On-line error monitoring of capacitive voltage transformer based on substation topology and distribution analysis

Abstract

Abstract The capacitor voltage transformer (CVT) is widely used in power systems with high voltage levels. The operation state of CVT is related to the accuracy of electric energy metering. Because the internal structure of CVT is complex and vulnerable to the external environment, the error may be out of tolerance in the actual operation process. The error is composed of system error and random error. The change of error is mainly the change of system error. In general, random errors satisfy specific distributions and will not change easily. In this paper, the voltage amplitude and phase effective value output by the CVT acquisition device at the same voltage level are used to compare the amplitude effective value of the in-phase output to obtain the ratio characteristic quantity K, and the phase effective value is subtracted to obtain the difference characteristic quantity θK . K and θK contain the information of two CVT ratio differences and angle differences. The probability density distribution obeyed by K and θK during the normal operation of CVT is taken as the reference probability density distribution and compared with the probability density distribution to be measured during online monitoring. If the probability density distribution changes significantly, it shows that the ratio difference and angle difference have exceeded the difference under the premise of this paper. Finally, the contribution method is used to locate the out-of-tolerance CVT. In this paper, the online monitoring method is verified by simulation data. The test results show that the ±0.1% range ratio difference and the ±5′ range angle difference can be identified, and the online monitoring of the 0.1-stage CVT error is realized.