考虑保护配合动作随机性的电压暂降频次评估

Assessment on Voltage Sag Frequency Considering Randomness of Protection Cooperation

电力系统元件发生短路故障时,保护的动作决定了电压暂降持续时间。传统电压暂降频次评估重点研究了故障类型、故障位置、故障前电压、变压器绕组联接方式以及故障阻抗对电压暂降频次的影响,仅简单假设故障由主保护清除,未考虑保护配合动作对电压暂降持续时间的影响。为了更准确刻画电压暂降持续时间,从实际电网保护配置和定值的固有属性出发,基于马尔可夫状态空间法,建立了主保护与后备保护配合清除故障的概率模型,并根据电网保护定值定量确定各暂降持续时间的概率,提出一种考虑保护配合动作随机性的电压暂降频次评估方法。对IEEE-30节点系统和250节点系统进行了仿真分析,结果证明所提方法符合实际,原理简单且适用性强。

When short-circuit faults occur in power system components, the duration of voltage sag is depended by the fault clearing time of the protection system. In traditional assessments on voltage sag frequency the influences of fault types, the position where fault occurs, pre-fault voltage, connection mode of transformer windings and fault impedance on voltage sag frequency are emphatically researched, and it is simply assumed that the fault is cleared away by main protection while the influence of protection cooperation on duration of voltage sag is not taken into account. To depict the duration of voltage sag more precisely, based on inherent attributes of protection configurations of actual power system and their settings and using Markov state space a probabilistic model of clearing fault by cooperation of main protection with backup protection is built, and according to the setting of protection the probabilities of various durations ＆voltage sags are determined, then a method to assess voltage sag frequency, in which the randomness of protection cooperation is considered, is put forward. The proposed method has been applied to the IEEE 30-bus test system and a 250-bus system, and simulation results show that the proposed method is truthful and practicable, and its principle is sim^le.