Study On Performance Decline Characteristics And Simulation Moisture Test Of Electric Motor Train Unit Arrester

Metal oxide arrester（MOA）is widely used in railway system bec ause of its excellent nonlinear characteristics.When the EMU is subjected to overvoltage,i t can act quickly to avoid damage to electrical equipment.Due to the long-term influence of overvoltage,bad weather,frequent vibration and other factors during the operation of EMU,it is easy to cause the arrester to be damp and aged.Therefore,it is of great theoretical significance and practical value to determine the characteristics of arrester aging and damp fault for the safe operation and maintenance of EMU.The electrical performance and sealing performance of arresters with different operating mileages were tested,and the variation characteristics of electrical parameters of arresters with different operating mileages were analyzed.The electrical performance test results show that the performance of the arrester running to 4.8 million km still meets the standard requirements,and there is no obvious sign of degradation and deterioration,which can continue to serve.The maximum change rate of DC reference voltage(U_{1m A})before and after sealing test is 0.594%,which is less than 5%of the standard requirements.The maximum change of leakage current under 0.75U_{1m A} is 3.9μA,which is less than 20μA of the standard requirements.This shows that the test arrester does not appear sealing failure and the sealing performance is good.The tests of arrester accelerated aging,valve plate accelerated thermal aging and valve plate long-term stability were carried out,and the performance variation characteristics and aging characteristic parameters of arrester under aging were obtained.The results show that the performance of the aged arrester is stable and the high temperature has little effect on the performance of the valve plate.The tolerance performance of the valve plate of the arrester after disintegration is tested and analyzed.The research shows that the resistive current under U_{1m A} and 42 k V of the arrester after disintegration can better reflect the valve plate defect,which can be used as a criterion for the performance degradation of the arrester.Scanning electron microscopy（SEM）and energy dispersive spectrometer（EDS）were carried out on the valve plates of a certain type of fault arrester.The test results showed that the internal moisture of the arrester occurred.Based on this,a simulation moisture test platform was established to study the variation characteristics of fault characteristic quantities of arrester valve plates under different moisture levels.The research shows that in the case of severe moisture,U_{1m A} decreases by 28%compared with the normal state.At 42k V,the total current value reaches 1.21 m A,the third harmonic content reaches 33%,and the resistive current reaches 1.35 m A.In other words,the leak age current,the effective value of the total current,the third harmonic content and the resistive current under U_{1m A}and 0.75U_{1m A} can be used as the moisture criterion of the arrester.The finite element simulation results are consistent with the test.