Double Air-gap Current Transformer Applied to High Voltage Transmission Line On-site Mobile Comparison System

Abstract

To evaluate the feasibility of applying electronic current transformer(ECT) with double non-magnetic air gaps to on-site mobile comparison systems, we analyzed ECT from two aspects, namely its steady-state accuracy and its stability after multiple times of installations. Regarding the steady-state accuracy, we reduced the ratio error and the phase error of the ECT though optimizing the core parameters and some error compensation measures. Test results proved that the ECT with double air gap core could achieve level 0.2 of the National Standards of China. Meanwhile, the measurement stability was studied from two aspects, namely the ratio error and phase error caused by varying length of the non magnetic air gap, and lowering the eccentric distance error. Test results of the ratio error and phase error versus the gap length indicate that maintaining the measurement accuracy requires to strictly control the installation. Moreover, regarding the large eccentric distance error of the ETC with single iron core, we proposed to use two series connected cores with double air gaps, and the theoretical analysis and experimental results proved it to be quite effective. However, according to the results, applying the ECT with double non-magnetic air gaps requires further improvement of the ECT in accuracy.