Abstract.A three-dimensional (3D) magneto-hydro-dynamic (MHD) model of air arc plasma is built to investigate the frequency effects on the arc motion process with different number of splitter plates. Based on this model, the arc voltage and current density are obtained. The arc motion time is normalized with the frequency and compared at different numbers of splitter plate. The result shows that the normalized time and the arc voltage peak increase with increases of the number of splitter plate.

GIS equipment (gas insulated switchgear) is more and more popular in power system, and people often pay more attention to its discharge fault than other mechanical faults. But in the operation of GIS, besides discharge faults, mechanical faults are also a major cause of accidents. Therefore, we should give more research to abnormal mechanical vibration. At the same time, compared with discharge signal, mechanical vibration fault is more difficult to study. In this article, based on the size of real GIS equipment, we first built a three-dimensional model through COMSOL software to study the propagation characteristics of vibration signals. Simply considered, the bus air chamber is two-dimensional axisymmetric. Firstly, the natural vibration frequency of the equipment is calculated by finite element method, and the vibration propagation characteristics of GIS shield cover loose of the GIS equipment are calculated and analyzed. The simulation calculation shows that the longer the shell is, the lower the natural vibration frequency is. Therefore, we should pay more attention to the natural vibration frequency far away from 100 Hz, when designing and manufacturing GIS equipment, so as to avoid serious consequences caused by resonance. Because the basic vibration frequency caused by the loosening of shield cover is twice as high as the power frequency of 50 Hz. Then the 100 Hz simulation source is added to COMSOL model as the vibration source of loosening fault, and the propagation rule and characteristics of vibration fault about GIS are received. After the vibration fault occurs, the loosening vibration signal at the connection between the GIS shell and the basin insulator is the strongest. These conclusions by simulation also conform to objective rules and facts. Meanwhile it can guide us to arrange sensors reasonably and improve the signal-to-noise ratio of vibration detection signals.