花瓣状配电网主干线的自适应全线速动电流保护

Adaptive Full-Line Snap-Motion Current Protection for the Trunk of a Petal-Shaped Distribution Network

花瓣状配电网网架结构特殊、运行方式灵活多变,使得传统的电流保护难以整定.自适应电流保护可根据系统运行及故障状态修改保护定值,为解决上述问题提供了可能.文中从理论上推导了花瓣状配电网主干线的故障电流与故障点两侧线路阻抗的关联特性,故障点一侧线路阻抗的变化会对另一侧故障电流产生影响.分析保护背侧等效阻抗随故障点位置变化而变化的特点,且该特点导致现有自适应电流保护灵敏性存在严重不足的可能;然后,通过分析短路故障时保护安装处的正序电流与正序电压的关系特征,给出了无需计算背侧阻抗的自适应正序电流速断保护的整定公式;最后,在特殊的花瓣状网架结构中,利用线路故障时两端保护相继动作的故障电流变化量特征,实现限时电流速断保护的加速动作.综合电流速断保护以及限时电流速断保护加速方案,提出适用于花瓣状配电网主干线的自适应全线速动电流保护.仿真结果表明,自适应电流速断保护具有确定的保护范围,且保护范围不受线路长短以及系统运行方式的影响;结合限时电流速断保护与故障电流变化量判据的加速方案可以准确识别线路末端故障,可靠加速保护动作,与自适应电流速断保护配合实现花瓣状配电网主干线上保护的全线速动,且其性能优于其他工频单端量保护.

The special structure and flexible operation mode of a petal-shaped distribution network make it difficult to apply traditional current protection.However,adaptive current protection can modify protection settings according to system operation mode and fault status,so it is a potential solution for this problem.This paper derives the theoretical relationship between the fault current of the trunk line of a petal-shaped distribution network and the line impedance on both sides of the fault point,where a change in the line impedance on one side of the fault point will affect the fault current on the other side.Analyzing the characteristics of the equivalent impedance on the back side of the protection shows that it changes with the location of the fault,and this characteristic leads to the possibility that the sensitivity of the existing adaptive current protection is seriously insufficient.Analyzing the relationship between positivesequence current and positive-sequence voltage during short-circuit faults yields the setting formula for adaptive positive-sequence current instantaneous trip protection.Finally,in the special petal structure,the characteristics of fault current variation of successive actions of two-terminal protection in the line fault are used to accelerate the action of time-limited current instantaneous trip protection.Based on the comprehensive current instantaneous trip protection and time-limited current instantaneous protection acceleration scheme,this paper proposes adaptive full-line quickcurrent protection suitable for the main line of a petal-shaped distribution network. Simulation results show the adaptivecurrent instantaneous trip protection has a certain protection range,which is not affected by the length of the lineand the operation mode of the system. The acceleration scheme that combines the time-limited current instantaneoustrip protection and the fault current variation criterion can accurately identify the fault at the end of the line and canreliably accelerate the protection action. It cooperates with adaptive current instantaneous trip protection to realize thefull-line snap-motion of protection in the petal-shaped distribution network,and its performance is better than that ofother power-frequency single-ended protection schemes.