一种金属氧化物限压器动作电流不平衡度的预测算法

A Prediction Method of the Unbalance Current Among Parallel Columns of Metal Oxide Varistors

金属氧化物限压器(MOV)是串补(FSC)与可控串补(TCSC)设备中对串联电容器组进行工频过电压保护的重要设备之一,工频过电压具有作用时间长、能耗极大的特点,目前采用氧化锌阀片柱并联的方式解决耗能问题。因此,研究出合适的配片方法以及限压器电流不平衡度的预测算法对确保限压器的安全运行十分必要。文章给出了用于精确描述氧化锌阀片及阀片柱伏安特性的计算公式,并给出了经配片后的MOV阀片柱动作电流不平衡度的一种预测算法。测算结果显示,经配片后,限压器最大电流不平衡度不会超过5%。

Metal Oxide Varistor (MOV) is one of the key equipments preventing serial capacitor banks from power frequency overvoltage in both Fixed and Thyristor Controlled Series Compensators (FSC & TCSC). Up to now, parallel connection of multi columns of varistor elements is the only practical solution to suppress power frequency overvoltage which is of the feature with huge energy and long action time. To ensure MOV safe in service, it is very important to find out an appropriate way for combinating the varistor elements and a prediction method for predicting the unbalance current among parallel-connected varistor columns. This paper presents a general form of precise algebraic representation of the V-I characteristic for both every varistor element and varistor column, and it also presents a method for predicting the unbalance current among the MOV columns based upon the combination report of varistor elements for the MOVs. Prediction results show that the maximum current unbalance factor will be within 5% for the home-made MOV products.