Design And Research Of Insulator Leakage Current Monitoring System Based On Tunneling Magnetoresistance Effect Current Sensor

Insulators play a vital role in high-voltage transmission lines,and have a certain resistance to voltage and mechanical stress.If the insulators are damaged,it will have a great impact on the entire transmission line.In order to avoid accidents in transmission lines,it is necessary to detect the operating status of insulators in time.The current leakage current detection methods are mainly divided into two types: online monitoring and off-line monitoring.Off-line monitoring methods require a lot of manpower and financial resources,and there is a problem that the monitoring period is too long.Although this method can obtain the operating status of the insulator,But there may be a delay in warning.Online monitoring means can realize real-time monitoring of insulator operating status.Currently,the commonly used monitoring tools mainly include current transformers,shunts and Hall sensors,low sampling frequency,etc.Tunneling magneto resistive current sensor(TMR sensor)is a sensor that responds to current changes according to magnetic field changes.Compared with Hall sensors,it has lower power consumption,higher sensitivity,better linearity,and more Wide measurement range.This paper will design and study an insulator leakage current detection system based on TMR sensor.This paper firstly analyzes the principle and characteristics of TMR series chips,and uses the transfer function to reason about the open and closed loop structure characteristics and measurement influencing factors.Based on the actual measurement environment and measurement parameters,the chip is selected,and the signal acquisition capability of the chip is tested in two ranges of 0～100 m A low current and 100～1000 m A large current by building a test platform.The results show that the TMR chip can sensitively measure signals in these two ranges,and when the magnetic focusing ring is used,the measured signal has better linearity and is closer to the true value.Secondly,this paper uses COMSOL software to simulate the inner radius,width,opening size and relative permeability of the magnetic concentrating ring.Combined with the simulation results and the actual installation position,the structural design is changed accordingly.The position offset simulation of the magnetic concentrating ring is carried out.,it is concluded that the magnetic concentration effect is basically not affected when the position of the magnetic concentration ring is shifted;the air domain is established by software and a directional magnetic field is applied,and the shielding efficiency of the magnetic concentration ring is studied by calculating the magnetic flux density distribution in the air domain.The results show that the magnetic concentration The ring has a good shielding effect against stray magnetic fields.In order to further strengthen the shielding effectiveness,a shielding shell strategy is proposed,the effect of the shielding shell is simulated,and it is verified that the shielding shell has a significant effect.Thirdly,this paper uses STM32F407ZGT6 as the main control chip,and designs the power supply module,signal acquisition module,bias adjustment and temperature compensation module,communication module and circuit protection module according to the characteristics of the chip,which integrates signal acquisition and signal transmission.The Keil5 development environment is used to design the system program,and the relevant programs of the signal acquisition module,display module and 4G module are designed to ensure the realization of the device function.Finally,this paper adopts the artificial contamination test method.The insulator is washed and dried to be stained.After the stain is applied,the constant pressure method is used to pressurize the insulator.While pressurizing,the insulator is dampened.At the same time,the signal acquisition is carried out,and the collected signal is denoised by wavelet,and then three eigenvalues of the maximum value,the effective value,the ratio of the third harmonic to the fundamental wave are extracted,and the three eigenvalues of the two signals are compared respectively.Analysis,the results show that the leakage current signal collected by the developed leakage current monitoring system is close to the standard signal of the sampling resistor,which can be used for actual insulator leakage current detection.