Research On Two-dimensional Electric Field Measurement System For Electrical Tree Detection In Insulating Materials

Electrical trees generated by partial discharge in insulating materials are common causes of on-site accidents.This paper takes transformer oilimmersed insulating board,which is the most scarce detection means,as the main research object,and designs a set of two-dimensional distributed electric field measurement system for electrical trees detection in insulating materials.In the electric field measurement part,the voltage value associated with the boundary electric field value is obtained by using the principle of capacitance voltage division.Therefore,the voltage value can be used to detect the growth of electrical trees from the power frequency component and the partial discharge pulse component,and the measurement point is extended from the one-dimensional distribution to the two-dimensional plane distribution,so that it can be used to study the growth and development law of electrical trees in the two-dimensional direction.In terms of acquisition and storage circuit hardware,five identical sub-modules run in parallel,and each sub-module expands the sampling channel multiple times through an eightchoice analog-switch chip,and adds signal lifting and amplifying circuits.STM32F407ZGT6 is used as the main control chip to complete potential acquisition,and the data is quickly stored on a large capacity USB disk through the USB module.It can ensure that the system can automatically and continuously collect and store the data of measuring points in the whole test process,so as to detect the growth process of electrical branches in real time and online.Each sub-module can measure the potential value of 72 points on the plane,and the 5 sub-modules can extend the measuring points to 360 by running in parallel.At the same time,an independent STM32 chip controls the coordinated operation of each part of the whole system.In terms of software,the STM32 peripheral functions are developed reasonably through programming and the running logic of each part of the program is arranged reasonably,so that the main control chip STM32 can control the whole system to run in an orderly manner.After verifying the feasibility of each part of the above design method,the author designed the printed circuit board and the shield shell of the twodimensional electric field measurement system and carried out the verification test.From the power frequency response signal and the partial discharge pulse response signal,the system can be used for the real-time online detection of electrical trees in insulation materials.