真空断路器投切并联电抗器过电压故障分析

文中以某220 kV变电站20 kV系统侧由真空断路器开断并联电抗器过电压引发的事故进行了分析。基于电路理论阐述了真空断路器投切并联电抗器过程中的截流、复燃、多次重燃过电压产生的机理,运用PSCAD建立了20 kV系统电磁暂态仿真模型,对不同截流值、不同并联电容下系统母线侧与电抗器侧的过电压进行了计算。结果表明常规氧化锌避雷器只能限制过电压幅值,不能改变频率和陡度,且现有避雷器均为相对地避雷器,不能有效地抑制相间过电压;电抗器两端加装并联电容器(或阻容吸收装置)可降低过电压幅值和陡度,能较好地抑制真空断路器投切电抗器过电压。

Analysis of Over-voltage Caused by Vacuum-breaker Switching on/off Shunt Connected Reactance

This paper studies a failure caused by a 20 kV vacuum-breaker＇ shunt connected reactor over-voltage in a 220 kV substation. Based on circuit theories, the mechanism of over-voltage in the process of vacuum-breaker switching on/off its shunt connected reactor is interpreted. Through building the electromagnetic transient model of a 20 kV power system in PSCAD environment, the over-voltages at bus side and reactor side with different shunt connected capacitors are calculated. It shows that a regular lightning arrester can only restrict the magnitude of over-voltage, and has no impact on its frequency and gradient; existing lightning arresters are ground-based, which is ineffctive for restricting phase-to-phase over-voltage; and a reactor with shunt connected capacitor can both reduce the magnitude and gradient of over-voltage, which is effective to restrict the over-voltage in the process of vacuum-breaker switching on/off its shunt connected reactor.