单相断线坠地故障暂态特征及暂态选线方法适用性

Transient Characteristics of Single-phase Line Breaking and Grounding Fault and Applicability of Transient Line Selection Methods

配电线路断线坠地故障发生概率较大,且易引发人身触电、火灾等事故,其与普通单相接地故障的暂态电气量差异及已有暂态选线方法的适用性尚不明确。根据故障边界条件构建了小电流接地系统单相断线坠地故障等值电路,初步分析了理想场景下断线瞬间、接地瞬间暂态零序电压/电流特征,单相断线坠地故障暂态电气量与普通单相接地故障的差异以及已有暂态电流幅值/极性比较、暂态功率方向等选线方法的适用性。仿真结果表明,断线、接地瞬间均存在明显的暂态过程,其暂态特征与普通单相接地故障存在一定差异,但在特征频段内,断线及接地瞬间的暂态电气量约束关系与普通单相接地故障一致,已有暂态选线方法仍然适用,不过利用断线瞬间产生的暂态电气量进行选线灵敏度较低。最后,利用仿真对选线方法的适用性进行了验证。

In distribution networks, the probability of the line breaking and grounding fault is high, and it may cause electric shock,fire and other accidents. The differences of transient electric quantities between single-phase line breaking and grounding fault and normal single-line grounding fault and the applicability of existing transient line selection methods are not clear. The equivalent circuit of the single-phase line breaking and grounding fault in non-solidly grounded system is established by fault boundary conditions. The characteristics of transient zero-sequence voltage/current at the moment of line breaking and grounding in the ideal scenario are preliminarily analyzed. Also, the differences of transient electric quantities between single-phase line breaking and grounding fault and normal single-line grounding fault, and the applicabilities of the line selection methods of transient current amplitude/polarity comparison and transient power direction are analyzed. The results show that there is obvious transient process at the moment of line breaking and grounding, and the transient characteristics are different from normal single-line grounding fault.However, in the selected frequency band, the transient electric quantity constraint relationships at the moment of line breaking and grounding are consistent with that of normal single-line grounding fault. The existing line selection methods are still applicable, but the sensitivity of the line selection using the transient electric quantities generated at the moment of line breaking is low. Finally,the simulation is used to verify the applicabilities of line selection methods.