On-line fault diagnosis method for 110kV cross-linked polyethylene cross-connected cable based on trajectory method

Abstract

The invention discloses an on-line fault diagnosis method for a 110kV cross-linked polyethylene cross-connected cable based on a trajectory method, namely, a trajectory method formed by induction voltage and metal sheath grounding loop current measurement parameters. The on-line fault diagnosis method comprises the steps of collecting metal sheath grounding loop current and induction voltage parameters of the cable through an on-line monitoring system, transmitting the parameters to the MATLAB through a serial port, constructing a trajectory diagram integrating the two types of parameters within the same time period by using a fitting code, solving the parameters such as the long axis, the short axis, the area and the inclination angle, analytically comparing the difference between the trajectory diagram and a normal condition, and analyzing the change rate of the long axis, the short axis, the inclination angle and the eccentricity so as to accurately perform fault diagnosis. The method disclosed by the invention can overcome defects of the traditional on-line monitoring and fault diagnosis method, is higher in accuracy, can realize real-time diagnosis and can form a historical fault trajectory database. According to an online detection method for the induction voltage, the line adopts a cross-connected grounding mode, and measurement is performed at two ends of a sheath protector of a line cross-connected grounding box.

Description

technical field [0001] The invention relates to an on-line monitoring and diagnosis method for 110kV cross-linked polyethylene cross-interconnection cables based on a trajectory method, which is suitable for voltage levels of 110KV and above, and belongs to the field of electric power technology. Background technique [0002] Cross-linked polyethylene (XLPE) cables have the advantages of light structure, excellent electrical performance, and convenient laying, and have been widely used in high-voltage power grids. During the operation of the power cable, it will be affected by the complex external environment, such as multiple factors such as electricity, magnetism, heat, chemistry, and machinery. There may also be local defects such as insulating air gaps and protrusions during the manufacturing process, which will promote the gradual deterioration of the cable insulation. Aging will eventually cause partial discharge, leading to the breakdown of the main insulation of the ...

AI Technical Summary

Problems solved by technology

During the operation of power cables, they will be affected by the complex external environment, such as multiple factors such as electricity, magnetism, heat, chemistry, and machinery. There may also be local defects such as insulating air gaps and protrusions during the manufacturing process, which will promote the gradual degradation of cable insulation. Aging, eventually causing partial discharge, leading to the breakdown of the main insulation of the cable, resulting in a ground fault

The insulation of the outer sheath of the cable may have the following faults: First, the damage of the sheath leads to multi-point grounding of the metal sheath of the cable, and the circulation of the metal sheath causes loss and heat generation, which leads to local overheating of the insulation and accelerates the aging of the insulation, seriously affecting the life of the main insulation; Second, the insulation damage of the sheath leads to water intrusion, and the probability of water tree aging in the main insulation increases, which has a serious impact on the life of the cable

The third is that the induced voltage of the sheath is too high, which leads to partial breakdown and discharge of the cable, which seriously affects the normal operation of the cable.

[0005] Since the cable arrangement, length, load current value, cross-sectional area, and voltage level will all affect the circulating current value, the above standards are not universal in actual situations

Through the analysis of relevant examples, it can be found that only measuring the magnitude of the ground loop current cannot meet the needs of accurate monitoring of the current cable operation

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