Monitoring and analysis of electronic current transformer’s field operating errors

Abstract

The energy metering accuracy and relay protection reliability in power grid systems critically depends on the phase current measurement accuracy. Commonly manufactured electronic current transformers (ECT) may exhibit unacceptable errors during field operation. Our research platform targets to remotely monitor ECT’s errors caused by ambient temperature variation, load current, and adjacent phase interference. A 0.2% accuracy, 110kV, Rogowski coil-based ECT prototype was selected for field operation in over 2years of monitoring tests. Correlated field and laboratory tests showed ambient temperature-related errors of less than 0.1% in current ratio and 2′ in phase, findings consistent with the type tests. The load current and adjacent phase interference introduce negligible errors for load currents larger than 0.2In (where In represents the phase rated current). However, the phase error exceeds 20′ for load currents less than 0.2In, possibly leading to false conclusions. Based on the above influencing factors, standardize the 0.2% accuracy ECT’s error less than half of the error limit ensures acceptable field error levels.