Selective transient earth fault detection in polyphase networks involves comparing displacement voltage and null current curves, evaluating proportionality factor to detect earth leakage and direction

摘要

The method involves continuous sampling and storage of a displacement voltage and null current in an output, detecting the first time the voltage exceeds a threshold in the event of an earth leakage, storing the displacement voltage and null current until the defined earth leakage, computing the null current summation curve, determining the gradient and the offset between the stored curves and evaluating the proportionality factor. The method involves continuous sampling and storage of a displacement voltage and null current in an output, detecting the first time the voltage exceeds a threshold in the event of an earth leakage, searching in the memory after the null crossing and before the first earth leakage, storing the displacement voltage and null current until the defined earth leakage, computing the null current summation curve, determining the gradient and the offset between the stored curves and evaluating the proportionality factor to detect an earth leakage and its direction.