有源配电网电流差动保护判据研究

电流差动保护是解决有源配电网保护问题的有效手段。由于故障特征不同，应用于输电线路的差动保护判据不能直接移植到配电网中。针对上述问题，首先分析了有源配电网故障电流的幅相关系，并在幅相平面中给出适用于有源配电网的制动区域。进而提出了一种提升保护性能的扇形制动区设计方法。在此基础上，考虑有源配电网常见的CT饱和情形，进一步引入二次电流的谐波含量比和基波幅值比构造辅助判据。最后提出了抗CT饱和的整体电流差动保护方案。基于PSCAD/EMTDC的仿真结果证明，与常规差动保护判据相比，该方案在保证可靠性的前提下具有更高的灵敏度，且具有很强的抗CT饱和能力，能够满足有源配电网的需求。

The current differential protection criterion of active distribution networks

Current differential protection is an effective way to solve the protection problem of active distribution networks. The current differential protection criterion applied to transmission lines cannot be directly copied into distribution networks because of different fault characteristics. To solve this problem, the amplitude-phase relationship of fault currents in active distribution networks is analyzed first, and the restraining zone suitable for active distribution networks is given in the amplitude-phase plane. Then, a novel sector restraining zone design method is proposed to improve the protection performance. Then, considering the common current transformer (CT) saturation situation in active distribution networks, an auxiliary criterion is constructed by introducing the harmonic content ratio and fundamental frequency component amplitude ratio of the secondary currents. Finally, an overall current differential protection scheme resisting CT saturation is proposed. The simulation results based on PSCAD/EMTDC prove that, compared with conventional differential protection criteria, the scheme has higher sensitivity while ensuring reliability and it also has strong anti-CT saturation capability. This can meet the needs of active distribution networks.