超导磁体脉冲冲击下MOV的破坏特性微观分析

Microstructure Analysis of MOV Destroyed by Pulse

为了将氧化锌电阻阀片(MOV)用于超导磁体的保护,研究了MOV在高温超导磁体产生的脉冲下的冲击破坏过程中的电气特性变化;还通过破坏后MOV的金相分析、SEM微观分析以及成分分析,研究了MOV破坏前后的微观特性的变化;最后讨论了MOV在超导磁体脉冲破坏下的机理,并针对MOV用于在超导磁体保护提出了改进建议,认为保护用阀片应该采取低压大通流氧化锌压敏陶瓷材料,且应该在配方确定的基础上,探索先进的工艺技术改善阀片的性能。

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, the authors 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, the authors 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, the authors 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 the authors put forward the advice about MOV＇s amelioration when it is applied in HTS magnet protection.