A method for locating and diagnosing dampness of power cable intermediate joints based on input impedance spectrum

Abstract

The invention discloses a method for locating and diagnosing dampness of an intermediate joint of a power cable based on an input impedance spectrum. Firstly, the input impedance spectrum obtained by testing the cable under test is processed through time-frequency domain conversion and discrete Fourier transform to obtain the cable under test. The positioning spectrum function of the measured cable, the positioning spectrum function of the normal cable, and the judgment model of the damp condition of the intermediate joint constructed by the two or / and the dampness severity diagnosis model of the intermediate joint are combined, and the power cable intermediate joint Carry out high-sensitivity positioning and accurate assessment of the severity of damp, and give corresponding countermeasures for intermediate joints under different damp conditions.

Description

technical field [0001] The invention belongs to the diagnosis technology of the intermediate joint of electric cables, and relates to the damp positioning diagnosis technology of the intermediate joint of the electric power cable, and more specifically relates to a method for high-sensitivity positioning and diagnosis of the damp condition of the intermediate joint of the electric power cable. Background technique [0002] With the wide application of power cables, the use of cable accessories is also increasing year by year. According to statistics, the early failure of cable accessories accounts for about 63% of the faults of the entire cable line. It can be seen that cable accessories have become a weak point in safe operation. The external environment of power cables is generally harsh, and the intermediate joints are usually located in the cable trench with perennial water, and the air is humid. If the waterproof measures during the installation of the intermediate join...

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Problems solved by technology

Cable defect location methods, including PD location under oscillatory waves or resonance, etc. Although the PD method is an effective method to detect the cable insulation state, its detection sensitivity is easily affected by the complex on-site electromagnetic environment

The patent application document with the application number CN201910612395.3 discloses a Chinese invention patent for a cable defect detection method based on the periodic attenuation characteristics of the oscillatory wave voltage. First, the partial discharge signal of the cable collected by the oscillatory wave test equipment is preprocessed, and then the obtained The time-distributed partial discharge signal is converted into a cycle-by-cycle phase distribution pattern, and the distribution of the discharge characteristic quantity of each cycle is counted, and the convolutional neural network is used to extract the characteristics of the discharge characteristic quantity of each cycle, and the abstraction of each cycle is obtained. feature expression, and then obtain the abstract feature sequence corresponding to the cycle, and finally use the recurrent neural network to process the abstract feature sequence corresponding to the cycle, and then perform classification prediction; although this method can accurately identify the cable defect type, its main detection Defects (such as impurities, knife marks, etc.), it is difficult to detect defects that reduce insulation such as moisture

The traditional time domain reflectometry (TDR) cannot accurately locate and effectively identify weak defects or intermediate joints due to the low high-frequency components contained in the input signal

The patent application document with the application number CN201410167827.1 discloses a time domain reflection method cable fault location simulation method. According to the operating parameters of the power cable under test, a simulation model is established using Pspice simulation software, and the cable is judged by the test waveform obtained by running the simulation model. The nature of the fault, but this method cannot accurately locate the middle joint of the power cable and evaluate its moisture content

[0004] In fact, the damp location diagnosis of the middle joint of the power cable is different from the location diagnosis of other local weak defects, because after the power cable containing the middle joint is tested by a broadband impedance spectrometer, in the middle joint positioning spectrum obtained, the middle joint It is a distortion point in itself. Even if the positioning spectra of the three phases of cables a, b, and c are compared, it is impossible to judge the moisture content of the middle joint of the power cable

Moreover, today's detection and diagnosis technology for intermediate joints of power cables is still at the stage of low-sensitivity positioning and installation defect detection, and there is an extreme lack of diagnostic technology for high-sensitivity positioning of intermediate joints and the severity of moisture

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