断路器结构参数对GIS中特快速暂态过电压波形的影响

Effect of Breaker Structural Parameters on Very Fast-fronted Transient Overvoltage Waveform in GIS

550kV及以上电压等级的气体绝缘变电站(GIS)系统中一般采用双断口断路器,并装有均压电容。本文着重分析断路器均压电容、空载母线、接地开关状态等对GIS系统中特快速暂态过电压(VFTO)波形的影响。首先建立了考虑断路器结构的简化GIS分析模型,推导了系统中节点电压的频域解析解答,然后分析了断路器结构参数和接地开关状态对VFTO的影响。结果表明,随着断路器均压电容、对地电容变大以及断路器到隔离开关母线长度的增加,系统中VFTO主要频率变小,但各频率分量的幅值在不同节点处有不同的变化规律;空载母线末端VFTO幅值呈减小趋势,上升沿变平缓,变压器线圈处幅值变化比较小,上升沿陡度变化不大,但上升时间增大;接地开关断开时,断路器断口间电压较小,但断口对地可能产生过电压;接地开关闭合时,断口间和断口对地可能出现谐振过电压,在设计时应予以避免。

The double-fracture circuit-breaker with two grading capacitors is used in gas insulated substation（GIS） at 550kV and above voltage levels.This article focuses on the effect of some parameters of circuit-breaker on very fast-fronted transient overvoltage（VFTO） waveform in GIS,such as the shunt capacitance of circuit breakers,floating bus,grounding switch status and so on.First,a simplified GIS model considering the circuit breaker structure was established.The analytical solution in frequency domain of node voltage was derived out from this model.Then,the effects of these parameters were analyzed.The results showed that when the capacitances of shunt capacitors or the capacitance to ground or the length of bus between circuit-breaker and disconnector increased,the main frequency of VFTO decreased,but the amplitude of each frequency at different nods had different variations,indicating that the amplitude of VFTO at the end of the no load bus decreased,the rising edge tended to be gentle;the amplitude and the gradient of the rising edge at the entrance of transformer slightly changed,but the rising time increased.When the grounding switch was off,the voltage between the breaker fractures was low,but the voltage to ground might be higher;when the grounding switch was closed,overvoltage between the fractures and fractures to ground might occur due to resonance.Therefore these phenomena should be paid attention to in the design of circuit-breakers.