谐波对集合式并联电容器内部故障保护的影响

Impact of harmonics on the internal fault protections of assembling capacitor

集合式并联电容器在实际运行中发现其内部故障保护的误动率较普通电容器高,并且容量越大,保护误动率越高。根据集合式电容器内部结构特点,基于内部故障保护动作整定值设置的基本法则,从高次谐波对内部元件最大允许故障率的影响角度阐明了误动率高的原因;同时分别针对单星形、双星形和桥形等不同接线形式,通过数学解析方法定量分析了谐波对保护动作值影响的程度,发现大容量双星形或桥形集合式电容器在高幅值的合闸暂态谐波涌流作用下,内部元件最大允许故障率大幅降低,致使内部保护的实际动作值严重低于整定值,从而易导致误动的发生;依据分析结果提出了相应的预防措施。

In realistic operation,assembling capacitors have been found that the mal-actions of its internal fault protection are more than ones of ordinary shunt capacitor bank and the maloperation rate becomes higher with the increase of the capacity.With the configuration characteristic and the protective setting principle,this paper elucidates the reason of mistake actions via analyzing the change of maximum fault element limit number under the influence of harmonics.By the mathematical analysis,the magnitudes of harmonics impacting on relay actions are deduced for single star,dual-star and bridge connections respectively.As a result,in the switching-on transient duration,a high magnitude of harmonic rush current can cause the considerable decrease of maximum fault element limit and make the actual protective action value much lower than the setting specially for those high capacity of dual-star or bridge connections which internal protection easily occur mal-action.The paper also presents corresponding measure against the mal-operation according to the analysis results.