The counter time limit element equipped protected machine which are provided on power transmission side of the

摘要

PROBLEM TO BE SOLVED: To provide a protective relay and a protecting method in which time-limit cooperation does not collapse even if a back power supply at the transmission side is changed in an electric power system in which an overcurrent relay is used for the protection of the receiving side.;SOLUTION: The protective relay, which is provided at the transmission side of the electric power system having the overcurrent relay that has inverse-time characteristics at the receiving side, includes a distance relay means and an overcurrent relay means, which has roughly the same inverse-time characteristics as those of the overcurrent relay at the receiving side. Furthermore, a first step protection range, in which the setting of the distance relay means is instantaneously shut off, is set to approximately 80% to 85% of a line impedance value of transmission and distribution lines connecting the transmission side and the receiving side. When an output of the second step is used, the protection range, in which shutoff is output after a certain period of time, is set to approximately 120% of the line impedance value. The setting of the protection range of the overvoltage relay means is made to cooperate with the shutoff time limit of the overcurrent relay means at the receiving side inside the premise of receiving end.;COPYRIGHT: (C)2009,JPO&INPIT