Patent ID: 6501631
Filing Date: 2002-12-31
Classification: H02H

Abstract:
Method for protecting a zone in a power system, which zone comprises a number of transmission lines connected to power sources and a number of transmission lines connected to a number of loads where the power sources and the loads are arranged outside the zone, wherein the method comprises the steps of:continuously measuring all the incoming currents (Iin) to the zone, continuously measuring all the outgoing currents (Iout) from the zone, and continuously calculating the differential current (Id) according to Id=Iinâˆ’Iout, and continuously integrating Iin, Iout and Id according to IIN=&Integral;t1(t1+T)&it;Iin&it;&dd;t(5)IOUT=&Integral;t1(t1+T)&it;Iout&it;&dd;t(6)ID=&Integral;t1(t1+T)&it;Id&it;&dd;t(7)where T is the fundamental frequency cycle, whereby changes of the continuously integrated values IIN, IOUT and ID constitute indications of whether faults on the power system occur within or outside the zone.