Microstructure Analysis of MOV Destroyed by Pulse
WEI Bin, TANG Yue-jin, REN Li, ZHOU Yu-sheng, WEN Yuan-fang(School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China)
The Metal Oxide Varistor (MOV) has been widely applied to the power industry due to its high degree of nonlinearity and excellent capability to carry heavy current. The superconductor, which will bring the electric power industry an important change, improves the level of electric power industry. However, protective technology for superconductor is based on practical application. In order to investigate MOV which is used for protection of high temperature superconducting (HTS) magnet, thes firstly introduced discharge experiment that the charged HTS magnet discharged to MOV directly, and collected data about MOV and the HTS magnet in the experiment. After the discharged experiment, thes analyzed U-I characters of MOVs after they were destroyed by pulse which was released by HTS magnet, and selected some MOVs based on the experimental analytic results. Then the microstructure of MOVs was analyzed by means of TEM and EPMA etc, thes studied microstructure change of MOV, and analyzed the destroyed theory of MOV under this pulse. It is found that the effect of the material on HTS magnet impulse is more severe than lightning impulse sometimes, and material degradation occurs on the MOV in these conditions. Even in some case the MOV are found to burn out when it is subjected to big impulse current. Finally thes put forward the advice about MOV's amelioration when it is applied in HTS magnet protection.
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