Design of wide-range current transformer based on improved zero magnetic flux and turns compensation

In order to realize a wide-range measurement current transformer that can meet the requirements of measurement accuracy under a wide range of currents, this article analyzes the influencing factors of commonly used turns compensation. And based on influencing factors, the error of current transformer under different parameters is simulated. The study found that simply using turns compensation cannot meet the error requirements of a wide-range current transformer. This paper then uses a fixed compensation resistor based on the principle of zero magnetic flux to reduce the error under a wide range of primary current. However, this kind of improvement measures adopted for economy and large-scale promotion cannot achieve true zero magnetic flux. Coupled with the low initial permeability of the silicon steel core material, the accuracy under 1% of the rated current still cannot meet the requirements of wide-range transformer errors. In order to meet the measurement error of not more than 0.2% under the rated current of 1%~200%, it is necessary to combine the two methods of zero magnetic flux technology and turns compensation. And it is necessary to further optimize the parameters of the compensation resistance and the number of turns compensation. The research results of this article provide a certain reference for the design and implementation of wide-range current transformers.

I. Introduction

For the commonly used electromagnetic current transformers, due to the initial permeability of the core material and the saturation magnetic induction, when the primary current is less than 5% of the rated current or greater than 150%, the accuracy of the measurement will quickly deteriorate. The accuracy of the measurement under small currents deteriorates due to the small initial permeability of the core material. When the current is greater than the rated current, the accuracy deteriorates due to the saturation of the core material. Due to the various forms and occasions of electricity consumption, the range of load changes has become wider and wider. In order to reduce the measurement error under a wide range of currents, a wide range current transformer is required. Especially for measuring current transformers, in order to reduce measurement errors and avoid losses, high-precision and wide-range current transformers are required [1]-[3].