| 摘要 |
A protective relay for an electrical power distribution system and a method. The protective relay includes first and second current transformers arranged to sense a respective current flowing into a power line, and a voltage sensing device arranged to sense the voltage of the power line. The protective relay further includes a first and a second device for determining the direction of a fault within the system based on a current signal from the first and second current transformers and a voltage signal from the voltage sensing means. The protective relay further includes a third device for determining the fault direction based on a sum of the current signals from the first and second current transformers and a voltage signal from said voltage sensing means. A controller determines whether a fault is internal or external based on the fault directions determined by the first, second and third devices.
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