基于节点分支电流幅值的含DG配网差动保护原理

Differential Protection Scheme Based on Current Amplitude of Branch Node for Distribution Network With DG

电流差动保护凭借其绝对选择性、适于多源网络等的诸多优点在含分布式电源配电网得到了广泛的应用,但目前配网通信水平较低,易受电流互感器（currenttransformer,CT）传变误差的影响,使其难以满足对线路两端采样值的高同步要求。该文提出了一种基于节点分支电流幅值的含分布式电源（distributedgenerator,DG）配网差动保护原理,通过考虑CT暂稳态因素的影响,量化制定保护门槛的整定值,利用标量传输弱化差动保护对同步误差的严格要求。同时计及分析不可测分支对该保护可靠性的影响,利用DG并网处三分支节点的故障特性,建立节点分支辅助判据,消除主判据盲区。该方案简单易行,具有良好的耐同步和耐CT误差的能力,且对配电网线路复杂的实际情况具有良好适用性。最后通过Matlab/Simulink仿真验证了该方案的有效性。

Current differential protection is widely used in distribution network with distributed generations（DG） for its absolute selectivity and being suitable for multi-source network. However, prone to be affected by current transformer（CT） transmission error, low level of distribution network communication makes current differential protection difficult to meet synchronization requirements of sampled values at both ends of the line. In this paper, a differential protection scheme based on comparison of positive sequence current amplitudes is proposed. By analyzing influence of CT transient and steady factors, setting principle of protection threshold is established. Strict requirement of differential protection on synchronization error can be weakened through scalar transmission. Considering effect of unmeasurable branch on protection reliability, a branch node auxiliary criterion is established according to fault characteristic at the three-branch node, through which DG is connected to grid, to eliminate dead zone of the criterion. The proposed protection scheme is simple, feasible, and able to resist synchronization error sand CT errors, with good applicability to complex network. Finally, effectiveness of the proposed scheme is verified with simulation in Matlab/Simulink.