10kV power distribution cable intermediate joint positioning method

Abstract

The invention discloses a 10kV power distribution cable intermediate joint positioning method. Firstly, DFT processing is carried out on an input impedance spectrum of the head end of a cable to obtain an original positioning spectrogram, then a window function with excellent performance is selected to carry out windowing processing and normalization processing on the original positioning spectrogram, and according to the positioning spectrogram after windowing processing, a distortion area in the spectrogram can be reflected more visually, so that an intermediate joint is positioned more accurately. The 10kV power distribution cable intermediate joint testing device is completely suitable for 10kV power distribution cable testing requirements, high in testing speed, high in testing precision, portable and long in standby time, and by adding the second-order Nuttall self-convolution window for processing, testing of the 10kV power distribution cable intermediate joint can be achieved with higher sensitivity.

Description

technical field [0001] The invention belongs to the power cable state detection technology, relates to the positioning of the middle joint of the power distribution cable, in particular to a positioning method for the middle joint of the 10kV power distribution cable. Background technique [0002] With the advancement of urbanization, the use of distribution cables and their accessories is increasing year by year. Usually, 10kV distribution cables run in trenches with complex environments, and are extremely vulnerable to moisture intrusion and external force damage. The middle joint plays the role of connecting two sections of cables, and as a weak link in cable operation, the insulation performance of the joint itself directly affects the reliability of power supply. However, the distribution network cable lines are often intricate, and the loss of cable laying drawings or the uncertainty of laying lines will cause a lot of time-consuming when searching for the location of...

AI Technical Summary

Problems solved by technology

However, when analyzing and processing the test signal, the Fourier transform algorithm will truncate the data in a non-full period, resulting in spectrum leakage and fence effect, which greatly reduces the accuracy of spectrum analysis.

The patent application document with the application number CN201710088838.4 discloses a local fault point detection method for marine low-voltage power cables based on the FDR method. This patent uses standing wave reflection to realize the location of cable short-circuit / disconnection faults. The location of this method is accurate. The accuracy is determined by the wave speed ratio of the cable; however, it is difficult to accurately obtain the wave speed of the cable in the actual field test, and the accuracy of the wave speed ratio directly affects the positioning accuracy

The patent application document with the application number CN201910273071.1 discloses a method for locating local defects of cable lines, using the impedance spectrum of the inspected cable and the standard cable, and realizing the positioning of local defects of the cable through integral transformation, although the method It can identify and locate local defects, but the positioning curve will "oscillate" due to the lack of algorithms, and the selection of the integral factor will also affect the accuracy of positioning to a certain extent

The patent application documents with application numbers CN201610351358.8 and CN201910647888.0 disclose local defect location methods for power cables based on the frequency domain reflection method. The Kaiser window and the Rectangular window are used to suppress the spectrum leakage, but the Kaiser window needs to be selected by itself. The lobe attenuation coefficient is not suitable for simplified programming and field engineering applications, and the Rectangular window has poor performance of its own window function, which is not ideal for improving the sensitivity of local defect positioning and identification

[0005] At the same time, due to the use of the discrete Fourier transform (DFT) algorithm in the spectrum analysis process, it will cause spectrum leakage and fence effects, which will greatly reduce the accuracy of spectrum analysis.

Although the spectrum leakage and fence effect can be suppressed to a certain extent by windowed Fourier transform (WFT), and the accuracy of spectrum analysis can be improved, but the classical window functions (such as Hamming window, Blackman window, Kaiser window, etc.) are difficult At the same time, it meets the performance conditions of narrow main lobe, small side lobe and fast attenuation, so the performance of the classical window function is not superior enough

[0006] To sum up, the detection sensitivity of 10kV distribution cable intermediate joint detection technology is still low, which cannot meet the requirements of on-site testing

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