System and method for detecting earth fault of sheath of single-core power cable on basis of circulation measurement

Abstract

The invention relates to the field of detection on an earth fault of a sheath of a single-core power cable, in particular to a system and a method for detecting the earth fault of the sheath of the single-core power cable on the basis of circulation measurement. Circulation detection is carried out on the sheath of the cable in three earthing modes of single-end earthing, double-end earthing and cross interconnection earthing. Firstly, transformation of additionally arranged switching elements for various earthing boxes of the cable is carried out, so that each earthing mode can be conveniently and safely converted into the single-end earthing mode in the measuring process; then in the state, a circulation value of the sheath is measured; and according to a circuit theory model of a fault sheath circulation loop and experimental data in the single-end earthing mode, circulation characteristics at different fault earthing points are obtained so as to carry out fault judgment and positioning. In the whole process, the detection is simple, the calculated amount is small, and online detection can be realized.

Description

technical field [0001] The invention relates to the field of single-core power cable sheath ground fault detection, in particular to a single-core power cable sheath ground fault detection system and method based on circulating current measurement. Background technique [0002] For cables with a single-core structure, this will inevitably cause an induced voltage on the metal sheath from the electromagnetic principle. If the grounding method is improper, the induced voltage will form a large induced current on the metal sheath, which will cause the cable to transmit power. The capacity is greatly reduced, and it causes the metal sheath to heat up, which reduces the main insulation and shortens the normal operating life of the cable. Some domestic power operation departments have formulated their own standards for controlling the circulating current based on experience, and usually need to control the circulating current within 10% of the load current or below 10A. [0003] ...

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Problems solved by technology

[0004] The grounding methods of the metal sheath of the above three single-core cables must be reliably grounded at least one point during operation, but because the outer insulation of the metal shielding layer of the cable is mechanically damaged during laying or is subjected to chemical corrosion, mice and ants and insects after a long time of operation The metal sheath is grounded at multiple points, resulting in a rapid increase in its circulation, which threatens personal safety, damages cable insulation, shortens cable life, and reduces cable transmission capacity.

The monitoring methods for multi-point grounding faults of cable metal sheath include the method of measuring the insulation resistance of the metal sheath, the off-line pulse method, the DC high-voltage flashover method and the impact high-voltage flashover method, etc., but they are not very ideal and cannot be measured online.

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