考虑不可测T接负荷的配电网虚拟三端电流差动保护

采用电流差动保护可解决高比例分布式电源接入配电网引起的馈线保护问题。然而当馈线内存在不可测T接负荷分支时,差动保护只能利用被保护线路两端的数据构造判据,性能受到影响。为解决该问题,首先分析了不可测T接负荷对传统两端电流差动保护的影响。在此基础上,提出了一种虚拟三端电流差动保护方法。该方法将被保护线路内部的不可测T接分支等效为一个虚拟支路,利用故障前后线路两端的电压、电流数据估算该虚拟支路的电流相量,并与馈线两端的电流相量一起构成三端电流差动保护判据。仿真结果表明,该方法在无需T接负荷测量数据的前提下能够满足配电网在不同场景下的保护需求,相比传统的电流差动保护具有更高的可靠性与灵敏性。

Energy-based Directional Pilot Protection for Distribution Networks with IBDGs Considering Unmeasured Load Switching

Inverter-based distributed generations(IBDGs)are the main approach to utilizing clean energy in distribution networks(DNs).Compared with synchronous source,fault response of IBDG is very different.As a result,in DNs with high penetration of IBDGs,legacy protection schemes will no longer be applicable.In this paper,an energy-based directional pilot protection scheme suitabie for DNs with IBDGs is proposed.This scheme considers the large range of phase angle caused by IBDG integration and uses improved energy polarity criterion to determine fault direction.In addition,magnitude of energy is used to distinguish between faults and load switching to overcome maloperation of directional pilot protection caused by internal unmeasured load switching.The proposed scheme first uses local measured information to determine fault direction sign and then exchanges the direction sign with the remote terminal.This scheme does not require high-bandwidth communication and strict data synchronization,so it can be implemented at a low cost.Finally,simulation studies verify effectiveness of the proposed scheme.

考虑不可测负荷分支的有源配电网单相断线故障保护方法

有源配电网断线故障造成过电压、人身伤亡及电机损毁等事故时有发生,针对这一问题,首先分析了有源配电网断线故障后各节点负序阻抗以及断口两侧零序电压差。借鉴电流差动保护的思想,定义了负序差动阻抗,基于区内外故障时负序差动阻抗的特征差异,提出了一种基于负序差动阻抗的保护方法。该方法利用负序差动阻抗幅值作为动作量,利用其相位构造具有自适应性的制动阈值。其次,针对重载保护失效的情况,提出了将零序电压幅值差作为辅助判据。最后,分析了不可测负荷分支对上述保护判据的影响,并提出了通过比较负序电流幅值进行故障定位的方法。仿真结果表明,所述方法可以可靠定位,具有不受中性点接地方式、过渡电阻、负荷以及分布式电源影响的特点。