电容器组的容值误差研究及其在电容器组保护配置中的应用

STUDY ON ERROR OF CAPACITANCE VALUE AND APPLICATION IN PROTECTIVE RELAYING OF CAPACITOR BANK

并联电容补偿装置由许多单台电容器串并联组成。实际运行中 ,如果电容器组中多台电容器故障退出 ,将造成健全电容器的过电压和过电流 ,因此必须采取可靠的保护措施。由于单台电容器的电容值存在随机误差 ,而以往对电容器组保护的可靠性、灵敏性的分析与计算建立在用固定比值估算电容器组相间容差的基础上 ,所以保护方案的比较及选择缺乏科学性和理论依据 ,难以选出最佳保护方案。因此 ,对电容器组的容值误差及常用保护方式的整定计算、性能指标、适用范围和方案选择等问题作进一步分析与研究是十分必要的。作者运用随机误差理论对电容器组的电容误差值(文中称之为容差 )进行了分析与研究 ,对电容器组中多台电容器故障时 ,不同保护方案的动作整定值及可靠性与灵敏性等问题进行了深入的分析与比较 ,提出了可行指数的概念 ,并确定了不同保护方案的适用范围 ,为实际工程中合理选择最佳保护方案提供了理论依据。

Shunt capacitor bank consists of many single capacitors.In practice,if some capacitors in the bank are out of service due to fault,the overvoltage and overcurrent will occur at the remainders.For this reason it is necessary to take reliable protection measure.Because each single capacitor has its own random error in the capacitance value and in the past the analysis and calculation of the reliability and sensitivity of capacitor bank are established on the basis of estimating the phase to phase capacitance value error of capacitor bank by fixed ratio.Consequently the theoretical basis for the comparison and selection of protection schemes is not adequate and it is difficult to select an optimal protection scheme.Thereby,it is very necessary to carry out further study and analysis on the error of capacitance value of capacitor bank,the setting calculation of the protection mode in common use,their performance,scope of application and scheme selection.Using random error theory,the error of capacitance value of capacitor bank is researched in this paper.The setting values of different protection schemes,their reliability and sensitivity are thoroughly analyzed and compared when some capacitors in the bank are out of service due to fault. A new concept,named feasibility index,is put forward and the scopes of application of different protection schemes are determined.The result of the study can be available for reference in the selection of optimal protection scheme for capacitor bank.