环网中计及距离保护时限特性的电压暂降随机评估

为准确刻画环网中距离保护对电压暂降特征的影响,提出了综合考虑系统环网特性和距离保护时限特性的电压暂降随机评估方法.从距离保护实际动作原理出发,经短路计算确定距离保护动作时间,根据环网线路两端距离保护动作时间判定是否发生多级电压暂降,通过修正节点阻抗矩阵确定多级电压暂降幅值,并基于电压损失量的概念将多级非矩形暂降等效为矩形暂降.对250节点系统的仿真结果表明,作者提出的方法能有效量化距离保护时限特性对电压暂降幅值和持续时间的影响,且能避免对多级电压暂降的过估计,相比传统方法更符合系统实际运行情况.

Stochastic Evaluation of Voltage Sag Considering the Time Characteristic of Distance Protection in Meshed Network

Depicting the operation of protection coordination in a scientific way, is one of the key points to objectively evaluate voltage sag characteristic. The mapping relationship between protection operation and voltage sag characteristic has not been further researched by existing studies, which leads to censored information of voltage sag characteristic. With the consideration of meshed network characteristic and distance protection operation time, the characteristic of multistage voltage sag was determined by modifying nodal impedance matrix, then nonrectangular voltage sag could be converted to rectangular voltage sag based on the loss of voltage concept, and stochastic evaluation model of voltage sag considering the time characteristic of distance protection was quantitatively put forward. The proposed method had been applied to a 250-bus test system and the process control system consists of several sensitive equipment, with pilot protection and distance protection of different time characteristic to protect the lines, the characteristic of voltage sag and the disturbance on process control system were comparatively analyzed, the simulation results showed that the proposed method is reasonable, adaptive and can meet the practical application better.