Cable insulation monitoring method and system based on high-voltage power frequency and low-voltage ultra-low frequency

Abstract

The invention discloses a cable insulation monitoring method and system based on high-voltage power frequency and low-voltage ultralow frequency, and belongs to the field of cable insulation monitoring. The method comprises the steps: coupling a low-voltage ultralow frequency signal in a high-voltage power frequency cable line; respectively measuring zero-sequence ultralow-frequency active and reactive power average values at the head and tail ends of each line; calculating the average value and the standard deviation of the ultralow-frequency dielectric loss of each line; judging whether theaverage value and the standard deviation of the ultralow-frequency dielectric loss exceed set thresholds or not; calculating correlation coefficients between adjacent lines, and comparing the correlation coefficients with the average correlation coefficient; calculating the change rate of the ultralow-frequency dielectric loss average value of each line, carrying out normalization processing to construct a distribution function, solving the insulation degradation probability, and outputting the insulation degradation probability when the insulation degradation probability is greater than the basic proportion. According to the invention, on the premise of realizing cable insulation online monitoring, various data processing methods are utilized to formulate an evaluation basis for a specific line, and the cable insulation state is evaluated timely and accurately.

Description

technical field [0001] The invention belongs to the field of cable insulation monitoring, and more specifically relates to a cable insulation monitoring method and system based on high-voltage power frequency and low-voltage ultra-low frequency. Background technique [0002] Most cable insulation breakdown accidents are caused by water tree branches, which is due to the low voltage of water tree branches under AC voltage. Impurities, protrusions, etc. form high electrical stress, and the insulation is damp to further promote the generation of water branches. In fact, water tree branch grows slowly, and its partial discharge signal is weak, which is not easy to detect. Once water branches induce electric branches, the insulation damage will be accelerated, and insulation breakdown may occur in a short time. Therefore, early detection of cable insulation defects is of great significance. [0003] At present, the cable insulation monitoring methods mainly include partial dis...

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Problems solved by technology

[0007] In view of the above defects or improvement needs of the prior art, the present invention provides a cable insulation monitoring method and system based on high-voltage power frequency and low-voltage ultra-low frequency, thereby solving the problem that the existing technology cannot timely and accurately evaluate the aging state of cable insulation technical problem

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