PROTECTIVE RELAY SYSTEM WITH SPACIAL DIFFERENCE FILTER AND SUMMING FILTER

摘要

A protective relay system which judges whether or not the fault section of a power system exists within a perscribed extent is constituted of a first spacial difference filter having a transfer function (Z-k-Z-q) in which the inputs are the voltage v¿m? and the current im at sampling time tm of the power system, and the outputs are a voltage vsm and a current ism, a second spacial difference filter having a transfer function, (1+Z?-1+Z-2¿+ ... +Z?-n)(1+Z-1¿) in which the outputs are a voltage v¿jm? and a current ijm, a controlled variable calculating means which calculates the reactance value Xm based on a formula, Xm=(-vsm.ism-p+ism.vsm-p)/(-ijm.ism-p+ijm-p.ism) (where, the voltage vsm-p, the current ism-p, the voltage vjm-p and the current ijm-p respectively represent the outputs of the first and second spacial difference filters at time tm-p), and an operation judging means which judges whether or not the reactance Xm is equal to or smaller than a set value Xs.