Research On High-frequency Small Current Measurement Based On Rogowski Coil

High-frequency small currents can be seen everywhere in daily life and industrial production,and their harmful phenomena are becoming increasingly prominent.In order to avoid the adverse effects caused by high-frequency small currents in daily production,it is of great research value whether it can be accurately measured.The rise time is very short,only 0.7 nanoseconds to 1 nanosecond,and the high-frequency components are extremely rich.The electrostatic discharge current with a small current amplitude of only a few amps to tens of amps is a typical high-frequency small current.This article researches and analyzes how to measure the electrostatic discharge current based on the Rogowski coil.The working principle of Rogowski coil and two different working states are analyzed,and the basic theory of Rogowski coil working in self-integrating state is emphasized.The effects of the number of turns,the integral resistance,the relative permeability of the magnetic core,and the core size on the high-frequency characteristics of the Rogowski coil are analyzed through simulation,which provides guidance for the development of Rogowski coils in the next step.Based on the method of controlling variables,the core size,the relative permeability of the core,the integral resistance,the number of turns of the coil,whether or not a matching resistor is added,and the winding method,and the coil sensitivity are studied experimentally to obtain the influence of each parameter on the measurement results of the Rogowski coil.Experimental results show that Rogowski coils made of nickel-zinc ferrite as the core skeleton material are more suitable for measuring high-frequency signals with extremely short rise times than Rogowski coils made of manganese-zinc ferrite as thecore skeleton material.The core size has a greater impact on the part of the waveform that is located at the wave head.The smaller the core size of the Rogowski coil,the higher its frequency characteristics will be significantly improved.As the number of turns of the coil increases,the overall measured waveform of the coil will shift upward;as the integral resistance increases,the waveform of the measured result of the coil after the first peak of the discharge will drop significantly as a whole.By reducing the number of turns and integration resistance of the coil,the upper limit cutoff frequency of the coil is effectively increased,and the accuracy of the measured waveform is higher when measuring the electrostatic discharge current.During the measurement,due to the addition of matching resistors,the oscillations on the waveform have been significantly reduced.When making the coil,the turns are wound in a single layer uniformly,which can effectively reduce the measurement error and the higher the accuracy of the measured waveform.This article develops a Rogowski coil suitable for measuring electrostatic discharge current with a sensitivity of 10A/V.It is verified on the established electrostatic discharge experiment platform that the measurement results are very similar to the waveforms measured by the standard squirrel-cage shunt.The first peak discharge current,the current value deviation at 30 ns and 60 ns does not exceed ±5%.The response time of the Rogowski coil was calibrated on the nanosecond square wave current source experimental platform to be less than 0.71 ns.