大容量金属氧化物限压器通风冷却结构优化设计与计算分析

Calculation and Analysis on Ventilation Structure of Different Optimum Proposals in Large Capacity Metal Oxide Varistor

大容量金属氧化物限压器(MOV)作为故障限流器的关键组件,在系统短路故障时吸收短路能量而导致本体温度瞬间升高,MOV的运行可靠性依赖于其通风冷却结构的散热能力,因此,合理优化MOV通风冷却结构具有重要的工程实际意义。本文在前期大容量MOV结构设计和大量实验研究基础上,提出两种通风冷却结构优化方案。根据计算流体力学原理并应用有限体积法,对初设方案以及两种优化方案的MOV流场流速和温度场进行了系统的计算分析。结果表明,相对于初设方案,方案一及方案二经过优化的通风冷却结构能使流体带走更多MOV内产生的热量,其最热点温度分别下降了约35℃和40℃,MOV芯柱的散热效果有了显著的提高。方案二在方案一的结构基础上,增加了径向冷却通风孔,其散热效果明显改善。在此基础上,实现了方案二的结构制作,并以此进行了实际工况下MOV温升的实验测定和进一步的计算,验证了优化方案的可行性以及相应计算方法的可靠性。

As a key component of fault current limiter（FCL）, metal oxide varistor（MOV） will absorb short-circuit energy during the short-circuit fault in power system, leading to the instantaneous increase of its temperature. The heat transfer ability of air-cooling system is of critical importance for the MOV reliability. Therefore, it is very important to reasonably optimize the ventilation structure of MOV used in power system. In this work, based on the structure design of large capacity MOV performed early and its corresponding experimental researches, two optimization designs of MOV structure（marked by MOV-1 and MOV-2, respectively） are proposed. With CFD principle and finite volume method, the fluid field velocity and temperature distribution of both basic MOV structure and the two optimized ones are systematically calculated and analyzed. It is shown that when compared to basic MOV structure, more heat can be taken away from the optimized MOVs and the decrease of the maximum temperature of the two optimized MOVs is about 35~C and 40~C, respectively, indicating their evident improvement of heat dissipation. In addition, the MOV-2 is obtained by adding the radial air-cooling hole on the basis of the MOV-1, and its heat dissipation is obviously improved, compared to the MOV-1. According to this, a practical MOV-2 was constructed and its temperature increase was experimentally determined. Good agreement between the determined temperature increase and the corresponding theoretical calculations is obtained, showing that the MOV-2 can be implemented in power system and indicating the reliability of the calculations performed in this work.