The charging process on sensor's shell in ion flow field and its influence towards electric field near HVDC lines

Abstract

Corona discharge appears near the HVDC lines when the surface electric field strength of the line is higher than the corona incept field. Ion flow will be formed under the affection electric field near conductors. Ion flow is a non-equilibrium plasma at low temperature, they are distributed among lines and the earth. Measurements of the DC synthetic electric field is important for the evaluation of the EMC of electric devices. Among several measuring methods, MEMS sensor is a new but useful one. When a MEMS electric field sensor with packaging is put into the area, charges will accumulate onto the shell of the sensor in a quick transient charging process and generate a reverse field. After the process finished, there exists an “empty zone” near the sensor where no charges in it. This paper studies the charging process of ion flow on packaging shell and the effects it cause, by using FEM simulation method and Multiphysics analysis, to provide theoretical basis for the design of MEMS sensors used for measuring electric field near HVDC. According to this paper, the effect of “empty zone” is lower than that of ion flow, the electric field changes it causes is about 50 V/m at the background target field 15 kV/m, while field changes caused by the ion flow among the area outside the sensor could be several dozen times of it.