Patent ID: 7710698
Filing Date: 2010-05-04
Classification: H02H

Abstract:
1. A protective relay for an electrical power distribution system comprising one or more power lines, said protective relay comprising: a first and a second current transformer arranged to sense a respective current flowing into a power line, a voltage sensing device arranged to sense a voltage of said power line, a first device for determining a direction of a fault within the system based on a current signal from said first current transformer and a voltage signal from said voltage sensing means, a second device for determining the direction of a fault within the system based on a current signal from said second current transformer and a voltage signal from said voltage sensing means, a third device for determining the direction of a fault within the system based on a sum of the current signals from said first and second current transformers and a voltage signal from said voltage sensing means, and controller means for determining whether a fault is internal or external based on the fault directions determined by said first, second and third devices.