The research and application on interfacing technology between Electronic Current Transformer and relay protection

The Electronic Current Transformer based on Rogowski coils (ECT) has many advantages, such as simple insulation structure, immunity to electromagnetic interference, no saturation effect, no flammable materials such as oil, and lightweight, etc. As a result, ECT has been considered as the appropriate substitute of the traditional electromagnetic current transformer. But the ECT is new equipment in power system, so the interfacing technology between ECT and relay protection is still immature, even the reliability of the relay protection system is decreased by the application of ECT. Based on the dynamic simulations that was carried out by Zhejiang Electric Power Corporation, the paper investigated the effect of application of ECT on relay protection equipment, such as the inconsistency between data from the duplicate analog-to-digital converters (AD), error output data of ECT at certain condition, error resynchronization of Merging Unit (MU), etc. An analysis of those problems is presented, the improvement of relay protections and ECT are proposed. Those improvements are verified by simulation.