Design Of High Potential Current Acquisition System And Its Application In Gap Discharge

Discharge current is an important physical parameter reflecting the process of long gap discharge,and the measurement of current is an important means to study the mechanism of discharge.The discharge current has high frequency,besides the amplitude of current shows significant difference in diverse phase of discharge.At the same time,as the charged particle discharge channel will dissipate in the discharge process,methods such as measuring current with Rogowski coil or using sampling resistor at low potential side,can meet the requirement of measuring range,but fail to ensure the accuracy of finite precision security.In order to measure the discharge current accurately,it is necessary to develop a set of high potential current acquisition system.Firstly,a set of high potential current acquisition system based on light triggering and optical signal transmission is developed in this paper.The system is divided into two parts:high voltage side including sampling circuit,data acquisition card and photoelectric conversion device and low voltage side including PC terminal and trigger source,transferring collected data and trigger signals by optical fiber.The gas discharge tube is used to protect the measuring equipment from overvoltage,and the synchronous circuit is used to trigger the current acquisition system and other measurement systems.The performance of the system is tested in the laboratory,which shows that it has good shielding function,low noise and good electromagnetic interference resistance.This system has good frequency response characteristics,its bandwidth is about 90MHz,the minimum rise time while measuring steep pulse is less than 4.8ns.Compared with PEARSON 8585C test coil,the amplitude error is less than 2%,which indicates this system can meet the requirements of high-voltage discharge current measurement.Based on the current measurement system,the switching impulse discharge current of the gap between huge grading ball and ground under rain condition is measured in this paper.Through the comparative analysis of the discharge images and current waveform,it is discovered that under rain condition,the ball-ground gap incept streamer discharge at lower voltage,and the leader channel develop faster.