特高压气体绝缘开关设备中电磁式电压互感器耐受特快速暂态过电压的特性分析

Withstand Characteristics Analysis of Inductive Voltage Transformer in UHV Gas Insulated Switchgear Under Very Fast Transient Overvoltage

为满足系统同期合环的要求,特高压气体绝缘开关设备(GIS)中安装有电磁式电压互感器(IVT)。GIS内部隔离开关操作会产生特快速暂态过电压(VFTO),可能引起IVT绕组出现电压分布不均的问题。为掌握特高压工程用GIS IVT在VFTO下的耐受特性,采用仿真和实测相结合的方法对其绕组在VFTO下的电压分布进行了研究。建立了IVT的端口模型和绕组电压分布计算模型计算其端口VFTO和绕组电压分布,并通过陡前沿冲击电压下绕组电压分布试验予以验证。通过仿真计算,获得了特高压变电站IVT端口的典型VFTO波形及其作用下的绕组电压分布特性。计算表明电压沿绕组分布整体比较均匀,绕组端部匝间、层间开口位置电压分布相对集中,试验结果初步也验证了仿真结果。根据仿真和试验结果,校核了绕组电压分布集中位置的绝缘耐受能力。进一步说明在实际特高压工程中,IVT绝缘耐受VFTO具有足够的裕度;在产品的优化设计中须加强绕组首端匝间和层间绝缘,以进一步提高其VFTO耐受能力。

Inductive voltage transformer （IVT） is installed in ultra-high voltage （UHV} gas insulated switchgear {GIS} to meet the requirements of synchronization loop operation in power system. Very fast transient over-voltage （VFTO） will be generated by switching the disconnector inisde GIS, and it may cause uneven voltage distribution in the winding of IVT. To get the withstand characteristics of IVT under VFTO, the voltage distribution in windings of IVT in UHV GIS under VFTO was investigated by both simulation and measurement. A port model of IVT and a simulation model were established for calculating the VFTO waveforms at the ports and the voltage distribution of the windings, and the results were verified by tests under steep front impulse voltage. The calculation shows that the voltage distribution along the winding is approximately uniform, but it is relatively concentrated at the interturn end and layer opening. Moreover, the result was primarily validated by the tests. Based on the results of simulation and test, the withstand ability of the winding insulation at some weak points in IVT was examined. It is concluded that that the insulation strength of IVT in UHV project under VFTO has an adequate withstand margin. However, it is favorable for strengthening the insulation among inter-turns and layers at the head of the windings during the structure design optimization so as to further improve the VFTO withstand ability of IVT.