复式比率制动差动元件中制动系数取值分析

Selecting Magnitude of Ratio Check Coefficient in Complex Percentage Differential Relay

在制动量中引入差动电流,构成复式比率制动特性.该特性制动系数的选取,应保证在内部短路故障时,计及流出母线电流的情况下,差动元件也能可靠动作;在外部短路故障,TA饱和而产生较大的误差时,也能保证安全性.通过分析提出同时兼顾内外故障时制动系数的取值范围;同时说明了双母线分裂运行和并列运行时差动保护的大差元件应取高低不同的制动系数.

With the differential current introduced in restraint portion, the complex percentage check characteristic is made up. The selection of magnitude of ratio check coefficient must ensure that the differential relay can operate firmly even when a fault occurs in a bus internally and the outflow of bus current exists, and that the differential relay do not operate even when the TA saturation brings about errors which are out of protection zone. This paper proposes a selection area of ratio check coefficient, which fits both the internal and the external faults, and points out that the check coefficient of large differential relay must be differentiated, when bus is operating in break-up or in parallel.