发电机失磁保护低电势圆的推导及其动作特性分析

Induction of the low potential criterion for loss-of-excitation protection and its action analysis

水轮发电机失磁后,进入静稳边界的时间很短,且不允许发电机在异步状态下运行,必须直接动作于跳闸,因此,尽早正确地检测出失磁故障,就显得意义重大。发电机失磁后,一个明显的特征就是低电势。基于以无穷大系统电压为参考相量的电压相量图,利用电压平面、阻抗平面、导纳平面之间的互演关系,对柳焕章先生提出的发电机失磁保护低电势圆判据进行了推导,并对低电势圆的动作特性进行了分析和仿真。得出低电势圆具有很高的灵敏度和反应速度。同时,对于主变高压侧短路故障引起的干扰,低电势圆具有很强的识别能力。仿真结果证明了推导过程和推理过程的正确性。

Since hydraulic generator runs into asynchronous state quickly and its sequent is very seriously, the response time of loss-excitation protection means lot to the hydraulic generator. Low potential is one of the most important characters while the generator is in loss of excitation process. Based on the generator voltage vector diagram, a low potential criterion has been well discussed in this paper by utilizing three panels： voltage panel, impedance panel and conductance panel. The action of the low potential criterion has also been studied carefully. It shows that the low potential criterion is more sensitive, has shorter react time, even it can distinguish the loss-of-excitation and the short circuit fault occurs on the high voltage side of the main transformer. Simulation results given in the end of the paper proved its validity.