Development method and comparative analysis of measurement accuracy of new broadband and wide range current transformers

The accuracy, safety, and reliability of current transformer metering are related to the accurate operation of secondary relay protection equipment and the fairness of power trade settlement. However, at present, many power users have a load that exceeds 120% of the rated current or less than 1% of the rated current. At the same time, a large number of power electronic equipment access to the distribution network injected a large number of harmonic components, the frequency range is large. For these situations, the traditional current transformer may not be accurate and must be developed for the power system frequency wide, the current fluctuation range of the wide frequency, wide range current transformer. Therefore, this paper researches the design of passive and active compensation technology and devices for wide frequency and wide range current transformers, and prototypes the passive electric type compensation current transformers and active electronic type compensation current transformers. On this basis, the paper also carries out the corresponding wide frequency and wide range measurement accuracy test verification and analyzes the performance of the two types of current transformers based on the test results, which provides a solution for the practical application of wide frequency and wide range current transformers.

I. Introduction

As an indispensable link in the power system, the distribution network receives electrical energy from the transmission grid and distributes it to various customers locally or by voltage step by step through distribution facilities. Among them, the 10 kV distribution network is used to supply electricity to urban and rural residents and is closely related to their lives [1]–[2]. In the 10 kV distribution network, the current transformer assumes the important role of transmitting the current information on the primary and secondary sides and is the guarantee of safe operation of the power system. It converts the AC current of the primary system into the AC current of the secondary system proportionally for use in various secondary systems, including protection systems, measurement systems, and metering systems. At the same time, the current transformer has the function of ensuring personal safety.