大型汽轮发电机定子绕组接地故障零序电压的数字仿真

Digital Simulation for the Zero Sequence Voltages of Large Turbo-Generator With A Stator Ground Fault

本文依据大型汽轮发电机定子绕组的结构(如极数;线圈组及相绕组联接方式等等),建立了新的接地故障时零序电压的数字仿真模型。某些难以处理的因素会使机端对中性点三次谐波电压之比值在不同正常运行工况下发生变化,对此本文则建议用实测值来修正仿真结果,并给出一种简便的修正方法,该仿真可被用来分析各种定子接地故障保护方案的特性。

A new simulative for the zero sequence voltahes of large turbo-generator with a stator ground fault is presented in this paper. The digital simulation can be used to obtain correct fundamental and third harmonic zero sequence voltages at the neutral and the terminal of the generator and flexiblely study the characteristics of various generator stator ground fault protection schemes.For the purpose of the simulation, eqiova;emt corciots based on the actual connection of coil-groups of the generators are built according to the distribution of the fundamentsl voltage and the third harmonic potential. Most large generators have a 60 degree phase band of the fundamental frequensy, so a 180 degree phase band of the third harmonic frequency, and their nutrals are grounded through a high impedance.In this case, the turn-voltage phasors under one pole, such as N pole, can then be constructed as an upper half circular arc of 60 degree for the fundamental frequency and 180 degree for the third harmonic frequency, and thar under the neighboring pole, such as S pole, as a lower hslf circular arc.The distribution of the fundamental voltage and the third harmonic potential depends on combining these circular arcs according to the number of poles and the connection method of stator winding of a cirtain generator, when a ground fault occurs, fundamental voltage and the thirs harmonic potential, as well as the distributed capacitance between the winding and the ground, are divided into two parts by the ground fault point.Based on that, a new simulative model os built after correctly processing of phase relation.All details for the simulation have been discussed about various large turbo-generator in this paper.