兴安直流C1不平衡保护采用计数方式的研究

摘要

This paper introduces the maloperation of C1 unbalance protection caused by disturbance in Xing-an HVDC project in recent years and analyzes the disturbance waveform. The internal structure of DC filter C1 capacitor, the principle and configuration of C1 unbalance protection are analyzed. The function of integration module INT that is vital to C1 unbalance protection program is analyzed. To avoid the C1 unbalance protection maloperation again, according to the development process of C1 capacitor unbalance faults, a modification is proposed for C1 unbalance protection. In the modification, the dynamic segment uses counting scheme to limit the impact of disturbance on the protection and to avoid maloperation. According to the overvoltage level caused by the C1 capacitor unbalance faults, different action strategies are arranged in the acceptable range of overvoltage level. When the number of short-circuit small strings is small and the overvoltage level is relatively low, alarm strategy is adopted; when the number of short-circuit small strings is big and the overvoltage level is relatively high, trip strategy is used.%介绍了兴安直流近年发生的扰动导致C1不平衡保护误动作事件，对扰动波形进行了分析。分析了兴安直流滤波器C1电容器结构特点，C1不平衡保护原理和配置。对C1不平衡保护程序中至关重要的积分功能模块INT进行了分析。为避免C1不平衡保护再次误动作，根据C1电容器不平衡故障的发展过程，提出兴安直流C1电容器不平衡保护修改方案。动态段采用计数方式，可以限制扰动对保护造成的影响，避免误动。根据C1电容器不平衡故障造成的过电压水平，在过电压可承受的范围安排不同的动作出口策略：短路小串数较少，过电压较低时告警出口；短路小串数较多，过电压较高时跳闸出口。