同步发电机励磁绕组匝间短路的仿真研究

转子绕组匝间短路故障会造成发电机励磁电流增大、输出无功减小、转子振动加剧等影响,如果不及早处理可能给机组的安全运行带来巨大威胁.近年来国内外研究主要通过实验检测及定性分析,由于不能准确计算故障电流等电气量,在实际应用中存在局限性.本文为多支路同步发电机励磁绕组匝间短路建立了改进的多回路数学模型,并提出了与励磁绕组有关的电感系数的计算方法,可以考虑气隙磁场畸变、定子绕组不平衡电流等因素的影响.针对1台4极凸极同步发电机,用该模型对不同匝数的励磁绕组匝间短路进行数字仿真,可得到短路后定、转子电流及有功功率、无功功率等.根据计算结果,本文提出励磁绕组匝间短路后定子同相不同分支之间出现分数次谐波环流、励磁电流出现基波及奇数次谐波的故障特征,并给出了物理解释,可以为转子匝间短路保护提供依据.

Simulation research on inter-turn short circuits of field windings in synchronous machines

When an inter-turn short circuit fault of field winding occurs in a synchronous machine,the field current will increase and the reactive power output will decrease,aggravating the rotor vibration.Severe damage will be caused to the safe operation of the machine if such faults are not handled properly in a timely manner.Existing research follows the experimental detection and qualitative analysis approaches,which are subject to practical limitations due to the fact that the fault current is not able to be calculated accurately.This paper proposes an improved multi-loop mathematical model for calculating the currents of stator and rotor as well as the active power and reactive power for the multibranch generator with inter-turn short circuit faults of field winding.Quantitatively evaluating the impact of air-gap magnetic field distortion and unbalanced current in phase windings hence becomes possible.Based on the calculation results,the paper gives a summary of the fault characteristics(e.g.,the existence of fractional harmonic circulating current and odd harmonic filed current) and their physical meanings,which may serve as the basis for the protection against inter-turn short circuit faults of field windings.