不接地系统中电磁式TV异常运行的仿真分析

用MATLAB软件仿真研究了中性点不接地系统中电磁式电压互感器在系统正常和接地故障运行的全过程 ,分析了TV励磁涌流造成熔丝熔断的规律性及开口三角绕组电压异常的原因。研究发现 :TV的励磁特性和高压绕组直流电阻、系统三相对地电容及其对称性以及系统的阻尼率均对TV励磁涌流有明显影响。另外 ,系统运行参数变化后还可能出现各种频率的铁磁谐振。电磁式TV在使用中应注意选用励磁特性好的产品、减少同一系统中TV中性点接地的数量、保持系统三相对地电容的对称性 ,同时注意高压绕组中性点的绝缘配合问题。

Digital Simulation Study and Analysis on Abnormal Operation of Electromagnetic Potential Transformer in Isolated Neutral System

By MATLAB, the transient process of TV in ungrounded power system is simulated, both in normal service or in some kinds of grounding fault conditions. This paper discusses the magnetizing inrush current flowing through TV and the abnormal overvoltage of opened delta-winding. It is found that the magnetizing inrush current could be influenced significantly by following factors; excitation characteristic, resistance in the primary winding of TV, line-earth capacitance and its symmetry as well as damping resistance of the network. Moreover, ferromagnetic resonance with various frequencies will occur if system parameter is changed. Some proposals are given: selecting TV with good excitation characteristic, reducing grounding number of TV in same network, keeping the symmetry of line-earth capacitance and paying attention to insulation coordination in neutral point of primary winding.