中小型水电站中发电机定子单相接地保护原理的探讨

针对中小型水电站的发电机提出了一种具有选择性的发电机定子单相接地保护原理,该原理是利用比较发电机各相之间出线侧与中性点侧差动电流工频变化量的关系来判断定子单相接地故障。理论分析和MATLAB仿真结果表明,正常运行时各相差动电流工频变化量的大小及相位相同;发电机外部系统单相接地时,故障相差动电流工频变化量的大小及相位与非故障相也一致;而发电机定子绕组内部单相接地时,故障相差动电流工频变化量远大于非故障相差动电流工频变化量,且方向相反。因此该保护原理可较好地区分发电机定子绕组内部单相接地和外部系统单相接地,其构成原理较简单、判别能力较强,有利于改善中小型水电站中发电机定子单相接地保护的性能。

Discussion on single-phase earth protection of generator stator in small-and-medium-sized hydropower station

This paper presents a new principle of generator stator single-phase earth protection with selectivity. This principle determines stator single-phase earth fault by comparing fundamental component mutation of differential current between phases. Theoretical analysis and MATLAB simulation result have shown that the fundamental component mutation of differential current of fault phase is the same as that of non-fault phase when single-phase earth fault is outside the stator and its value is more larger than that of non-fault phase and it is of opposite phase to non-fauh phase when single-phase earth fault occurs in the stator. This principle is of simpleness and strong distinguishing capability. It is beneficial to the performance improvement of generator stator earth protection in small-and-medium-sized hydropower station.