Apparatus and method for fault classification of three-phase distribution power cables

Abstract

A DC-component-based fault classification apparatus and method for a three-phase power distribution cable are provided. The apparatus and the method reconstruct three-phase currents by measuring the magnetic field around the cable with an array of magnetic sensors arranged around the cable surface (with a shielding cover being mounted to shield outer interference magnetic field), and a fault variety is determined through the DC components and polarity after a fault. A data acquisition system acquires analog signals from the sensors and a processing system extracts DC components, by mathematical morphology, in the analog signals for the phases during the transient period after a fault. These DC components arise in the faulted phases when a fault occurs since there is a large current changein the inductive power network.

Description

technical field [0001] The present invention relates to a device and method for classifying short-circuit fault conditions in three-phase distribution cables. More specifically, it relates to apparatus and methods for classifying by magnetic field measurements for reconstructing current and identifying the presence of a DC component in a phase during the transient period following a fault. Background technique [0002] Power systems require a reliable distribution network to ensure the quality of power delivered to customers. Although the power distribution cables are deployed underground to avoid bad weather conditions as well as for the aesthetics of the city. But faults are still common in these underground distribution cables due to internal insulation breakdown or external damage. For example, a phase-to-ground short circuit fault occurs during an insulation breakdown, resulting in physical contact between the phase conductors and the grounded screen. There may also ...

AI Technical Summary

Problems solved by technology

[0005](1) Pre-calibration requirements: the labor cost for setting the relay threshold is about 30% of the relay protection investment

This is becoming increasingly expensive as the world's electricity consumption and distribution networks expand dramatically

[0006] (2) Susceptibility to electromagnetic interference: due to electromagnetic coupling between faulted and normal phases, this can lead to erroneous fault classification results

This problem is exacerbated by the massive deployment of high-frequency electronic devices

[0007](3) Failure: Some technologies may not be able to identify three-phase short-circuit faults, because some characteristic quantities of three-phase short-circuit faults are still symmetrical as in normal operation

Although there are many transient methods to classify faults in post-fault conditions, there is still a lack of a fault classification method that does not require pre-calibration, is immune to electromagnetic interference, and can reliably identify three-phase short-circuit faults

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