基于广域保护系统的距离后备保护整定方案

A distance backup protection setting scheme based on wide area protection system

电网中发生潮流转移现象后,受影响的输电线路会承受大量的转移负荷,进入过负荷运行状态。距离保护后备段的整定要求躲开线路正常运行时的最小负荷阻抗,因此潮流转移带来的线路过负荷将会对距离保护后备段带来显著影响。针对这一情况,提出了一种能够应对潮流转移情况的距离后备保护整定方案。该方案基于广域保护系统,利用WAMS可测幅值与相角的特点快速计算线路的视在阻抗值。然后根据线路视在阻抗的变化幅度确定线路所承受的转移负荷比例,针对线路不同的过负荷状态进行与之对应的后备保护整定值调整,既防止过负荷线路上的后备保护发生误动,又使后备保护保有正确识别短路故障的能力。最后将整定信息与负荷波动情况上传至调度中心,为调度中心进行负荷控制提供辅助决策,并依据调度中心的决策进一步调整后备保护的整定值,直至线路恢复正常的负荷输送状态。以新英格兰10机39节点系统为样例,采用BPA仿真验证了该方案的有效性。

The transmission line affected by the flow transfer will enter a state of overload operation. The setting value of the distance backup protection needs to avoid the minimum load impedance. As a result, the flow transferring will bring significantly impacts to the distance backup protection. Focusing on this situation, this paper raises a distance backup protection setting scheme to cope with the flow transferring. This scheme is based on the wide area protection system. First, the WAMS is used to quickly calculate the apparent impedance value on the transmission line. Then, the flow transfer ratio on the lines is calculated according to the variation of the apparent impedance. For lines of different states of overload, the corresponding setting values adjustment method is used for backup protection. The adjustment method can not only prevent the mistake actions of the backup protection on the overload lines, but also can identify the short-circuit faults on the lines which are protected. At last, the setting information and load fluctuation are uploaded to the dispatch center as auxiliary information. So that the dispatch center can make a decision about the load control. On the basis of this decision, the setting value of the backup protection is further adjusted until the transmission line is returned to the normal state of load. The New England 10-unit 39-bus system is taken as an example. This method is verified by the BPA simulation.