分布式发电系统对继电保护灵敏度影响规律

Influence law of distributed generation on relay protection sensitivity

研究了分布式电源(DG)对过流保护灵敏度的影响规律,提出了多DG配电网的过流保护修正方案。利用单位电流法和多端口网络法对DG接入配电网后的等效电路进行了计算和分析,理论和仿真证明:单一DG对保护灵敏度的影响规律是由DG短路阻抗和接入位置决定的二次型;多DG接入系统对保护分支电流的影响特性近似看作各DG影响特性曲线的叠加;以系统短路阻抗中点为基准点,两侧按照DG短路容量顺序接入对保护分支电流的影响最小。对反时限过流保护的动作特性曲线进行正向修正和反向校核,使其保持正确的配合关系和配合裕度,从而消除DG对配电网过流保护的影响。

The influence law of DG（Distributed Generation） on the sensitivity of over-current protection is analyzed, and its revision scheme is proposed. The equivalent circuits of distribution network with DG are calculated and analyzed with the unit-current method and multi-port network method. Theory and simulation prove that： the mono-DG influence law is a quadratic curve, depending on DG short-circuit impedance and DG injection position; the multi-DG influence law is approximately the superimposition of all DG influence characteristic curve; the influence on protective branch current is minimized when DGs are injected from the central point of system short-circuit impedance to both sides according to their short-circuit capacity from small to large. The characteristic curve of inverse time current protection is forward revised and backward verified to keep correct coordination relation and coordination margin, thereby the influence of DG on over-current protection is eliminated.