摘要
为较好实现MOV内部过电压新保护方法,试验研究了MOV在空气、变压器油和液氮3种绝缘介质中的雷电冲击响应特性,进一步运用ANSYS有限元软件仿真分析了液氮介质中MOV在遭受雷击时的热特性。试验结果表明,MOV在多种介质中有效限制了雷击过电压,利于保护并联于MOV后的设备器件,其中以液氮介质中限压效果最好,平均低于空气介质中约200V;ANSYS仿真结果表明,在MOV与液氮的接触面上存在局部气化并产生气泡的可能性,严重威胁到液氮绝缘介质的电击穿强度,基于此讨论了改善MOV表面热梯度分布,提出了避免液氮局部气化的方法,为MOV应用于超导设备内保护提供了参考。
A new method for internal over-voltage protection of electrical equipment is presentd with MOV, but MOV submerged in insulation material can interact each other on some conditions, consequently the MOV performance of limiting over-voltage is influenced. To guarantee effectiveness of the protection method, the MOV characteristics of lightning in air, transformer oil and liquid nitrogen are experimentally investigated, and the ANSYS software is applied to calculate the thermal performance of MOV in liquid nitrogen when MOV is struck by lightning especially. Experimental results indicate that response voltage and current increase slowly along with quick raise of lightning voltage, so MOV in several media effectively restricts lightning over-voltage, and can protect operation safety of electrical equipment. The optimum limiting effects come from MOV in liquid nitrogen, and mean voltage is less than that in air by about 200 V. The impair of low temperature on MOV microstructure is main reason. Simulation results of the ANSYS software show that,at the temperature above boiling point of liquid nitrogen on the contact surface between MOV and liquid nitrogen, the gasification of liquid nitrogen on local contact surface is likely and severely threatens the dielectric breakdown intensity of liquid nitrogen. Several methods are discussed to improve thermal gradient distribution and avoid local gasification of liquid nitrogen on MOV surface.
出处
《高电压技术》
EI
CAS
CSCD
北大核心
2008年第1期33-36,共4页
High Voltage Engineering
关键词
MOV
雷电冲击
变压器油
液氮
热特性
温度分布
MOV
lightning
transformer oil
liquid nitrogen
thermal performance
temperature distribution
