电容式电压互感器一次侧过电流的原因分析

Analysis of the Over Current on the Primary Side of Capacitor Voltage Transformer

建立了电容式电压互感器(CVT)及其系统的等效电路模型,以35 kV CVT为例,分析了可能造成CVT一次侧过电流的各种原因。从幅相频率特性角度反映了CVT自身及其系统谐振点的分布情况,根据CVT中间变压器非线性激磁电感和速饱和阻尼器非线性电感的伏安特性试验数据,得到相应的磁化曲线,建立了CVT的仿真模型。利用ATP-EMTP电磁暂态仿真软件对过电流的原因进行了验证,仿真结果证明系统开关操作导致的CVT一次侧冲击涌流、CVT自身的串联谐振以及CVT与系统其它元件之间的并联谐振,是造成一次侧过电流的3种主要原因。最后对CVT设计给出了相应的建议。

An equivalent circuit model of capacitor voltage transformer （CVT） and its system is established. Taking a 35 kV CVT for example, the causes of the over current on the primary side of CVT are analyzed. The Bode-diagram of CVT and its system is derived to reflect the distribution of resonance points. According to the magnetization curve of nonlinear inductor of CVT＇s intermediate transformer and quick saturation damper, a simulation model is derived by the corresponding voltage-ampere characteristics. ATP-EMTP electromagnetic transient simulation software is used to verify the causes of over current on the primary side of the CVT. Results prove that the inrush current on the high voltage side of CVT, the internal series resonance, and the system resonance of the CVT are three major causes leading to over-current on the high voltage side of CVT. Some suggestions of CVT design are also offered.