微机保护实现自动判别失磁类型和预测失磁深度

Failure-Mode-Recognition and Loss-Degree-Prediction with Microcomputer-based Loss-of-Excitation Protection

本文通过对强制同步电势分量E_(t*q)和强制空载电势分量E_(fq*q)在失磁下的特性分析,得出失磁后E_(t*q)、E_(fq*q)衰减时间常数T_q仅取决于发电机参数及失磁类型的结论,提出了以T_q结合逻辑数判别失磁类型及预测失磁深度的方法,使微机失磁保护有可能在失磁发生的瞬间自动判别出失磁类型并预测失磁深度。数字仿真及动模试验验证了本文所提出的方法。

Up to now, every criterion involving generator loss-ot-excitation is not perfact in accurcy reliability and rapidity because they are all influenced by slip ratio, system perturbation and indefinite effects of energy-storaged elements in power system. Moreover, the protective relays based on these criteria can not differentiate various fault types. For avoiding the effects of the causes mentioned above, we have advanced two new crteria based on two deduced parameters named as Intrinsic Synchronous Generated Volatge and Intrinsic No-load Generated Voltage. The decay time constants oi the two voltages after faults merely depend on parameters of generator-self and fault types, they are not related to operation states of system and generator.In this paper we put forward a method to recognize failure modes of loss-of-excita-tion, to predict the degree of loss-of excitation and the ultimate excitation conditions of generator. The method's correctness have been proven by theory analysis, digital simulation and micromachine tests.The advantages of these methods provide realizability to select optimal protection schemes, to handle faults in good time, to prevent fault from extension, and help to analysis after faults.