A method for collecting partial discharge of cables

Abstract

This invention discloses a method for collecting partial discharge data from cables, relating to the field of power equipment condition monitoring technology. The method includes the following steps: S1: Using a fixing device, multiple ultrasonic probes are fixed in a circular array near the cable joint. After installation, the installation temperature of the cable joint to be tested is ensured. Then, a temperature control device is used to compensate for the temperature at the ultrasonic probes. After temperature compensation, the acoustic wave probes are used to collect acoustic signals from multiple locations at the cable joint. S2: After data acquisition, the weak signals received from the ultrasonic probes are amplified by a signal amplifier. After amplification, the measured signals are preprocessed. After preprocessing, singular value quantization combined with CEEMDAN threshold layering noise reduction is used. S3: After noise reduction, the filtered signals are subjected to spectral analysis, which can improve detection sensitivity, reduce signal attenuation, and effectively eliminate noise during the detection process, thereby improving detection accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of power equipment status monitoring, and in particular to a cable partial discharge collection method. Background Art

[0002] During the insulation manufacturing process of high-voltage cables, it is difficult to avoid some impurities remaining inside the insulation layer due to factory manufacturing processes and other reasons. During the operation of high-voltage cables, due to the aging and decomposition of the insulation layer, some dispersed foreign matter will be produced. The conductivity and dielectric constant of these impurities and foreign matter are very different from those of the insulating medium. Under the action of external voltage, the field strength of the parts where these impurities and foreign matter are located will be significantly higher than the field strength of the surrounding parts. As the external voltage increases, when the field strength of the parts where the impurities and foreign matter are located exceeds the ionization field strength of the cable at that location, the cable at that location will produce ionization discharge, that is, local discharge. Cables in local discharge are easily ignored by maintenance personnel. In order to ensure the quality and safety of the cables, staff are required to promptly discover problems and faults in the cables and quickly take effective measures to deal with them; Since partial discharge testing will produce electricity, sound, light, heat and other phenomena, there are many corresponding detection methods at present, including light detection, chemical detection, sound wave detection, pulse current method, ultra-high frequency method, etc. Since there is very large electromagnetic interference in the operation site of power equipment, the sound wave detection method is widely used in power equipment because it is not subject to electromagnetic interference; When using acoustic wave detection, the acoustic wave will gradually attenuate during the propagation process, especially in long distance and high impedance environment, the signal strength may become very weak, resulting in a decrease in detection sensitivity. At the same time, during the detection process, external environmental noise may affect the accuracy of the acoustic wave signal and increase the complexity of data analysis. Therefore, we propose a cable partial discharge acquisition method. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the existing defects and provide a cable partial discharge acquisition method, which can improve the detection sensitivity and reduce signal attenuation during the detection process, and can effectively eliminate noise and improve the detection accuracy, which can effectively solve the problems in the background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a cable partial discharge collection method, comprising the following steps: S1: Use a fixing device to fix multiple ultrasonic probes in a circular array near the cable joint. After installation, ensure the installation temperature of the cable joint to be tested, and then use a temperature control device to perform temperature compensation on the ultrasonic probe. After temperature compensation, use an acoustic wave probe to collect acoustic wave signals at multiple locations at the cable joint; S2: After data collection, the weak signal received from the ultrasonic probe is amplified by a signal amplifier, and the measured signal is preprocessed after amplification. After preprocessing, singular value measurement is used for quantization combined with CEEMDAN threshold layered denoising; S3: After noise removal, the filtered signal is subjected to spectrum analysis to identify the frequency characteristics of the discharge signal, and then the artificial intelligence algorithm is used to compare historical data with real-time data to identify different discharge modes; S4: After identifying the discharge pattern, the time-frequency characteristics of the discharge signal are extracted, and then analyzed by the PRPD module to further quantify the intensity and regularity of the discharge activity. After analysis, the PRPD module transmits the data to the display screen in the form of waveform graphs, spectrum graphs, etc. to visually display the change trend of the discharge signal, and stores the data in the data storage device for archiving. In this way, the collection can be completed and compared with the warning threshold after collection. Once abnormal discharge is detected, an alarm is immediately issued.

[0005] Further, the process of collecting the acoustic wave signal of the acoustic wave probe at the cable joint in step S1 comprises the following steps; S11. Clean and dry the cable test site to eliminate the influence of surface dirt and moisture on the test results; S12. Aim the ultrasonic probe at the cable connector to be tested and apply a pressure of 3-5 kg ​​to ensure effective transmission of the sound wave signal.

[0006] Furthermore, the fixing device in step S1 may be a clamp or a bracket. After installation, the ultrasonic probe must be stable and not shake. Furthermore, in step S1, the ultrasonic probe uses a piezoelectric ceramic sensor and a magnetostrictive sensor.

[0007] Furthermore, the pre-processing in step S2 is to remove background noise and other interference signals by using a bandpass filter, and only retain specific frequency components related to partial discharge.

[0008] Furthermore, in step S3, the artificial intelligence algorithm may use CNN or RNN, and the historical cable discharge characteristics may be input into the artificial intelligence algorithm before use to train and verify the artificial intelligence algorithm.

[0009] Furthermore, in step S4, when extracting the time-frequency characteristics of the discharge signal, the time domain signal is decomposed into multiple scales by using wavelet transform technology.

[0010] Furthermore, the setting of the warning threshold in step S4 is a cable discharge interval that is reasonably set based on the historical data and operating conditions of the cable.

[0011] Compared with the prior art, the beneficial effects of the present invention are: the cable partial discharge collection method has the following advantages: By setting up and using a high-sensitivity acoustic wave sensor and combining it with a signal amplifier, the detection sensitivity can be improved and the impact of signal attenuation can be reduced. At the same time, the measured signal can be pre-processed by adding a filter, and the singular value measurement quantification combined with the CEEMDAN threshold layered denoising can eliminate the environmental noise interference on site, improve the accuracy of the acoustic wave signal, and thus improve the detection accuracy. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] This embodiment provides a technical solution: a cable partial discharge collection method, comprising the following steps: S1: Use a fixing device to fix multiple ultrasonic probes in a circular array near the cable joint. After installation, ensure the installation temperature of the cable joint to be tested, and then use a temperature control device to perform temperature compensation on the ultrasonic probe. After temperature compensation, use an acoustic wave probe to collect acoustic wave signals at multiple locations at the cable joint; The fixing device can be a clamp or a bracket. After installation, ensure that the ultrasonic probe is stable and does not shake. The ultrasonic probe uses a piezoelectric ceramic sensor and a magnetostrictive sensor. S2: After data collection, the weak signal received from the ultrasonic probe is amplified by a signal amplifier, and the measured signal is preprocessed after amplification. After preprocessing, singular value measurement is used for quantization combined with CEEMDAN threshold layered denoising; Preprocessing is to remove background noise and other interference signals by using a bandpass filter, and only retain the specific frequency components related to partial discharge; S3: After noise removal, the filtered signal is subjected to spectrum analysis to identify the frequency characteristics of the discharge signal, and then the artificial intelligence algorithm is used to compare historical data and real-time data to identify different discharge modes; The artificial intelligence algorithm can use CNN or RNN. Before use, the historical cable discharge characteristics are input into the artificial intelligence algorithm to train and verify the artificial intelligence algorithm; S4: After identifying the discharge pattern, the time-frequency characteristics of the discharge signal are extracted, and then analyzed by the PRPD module to further quantify the intensity and regularity of the discharge activity. After analysis, the PRPD module transmits the data to the display screen in the form of waveform graphs, spectrum graphs, etc. to visually display the change trend of the discharge signal, and stores the data in the data storage device for archiving. In this case, the collection can be completed. After the collection, it is compared with the warning threshold. Once abnormal discharge is detected, an alarm is immediately issued; When extracting the time-frequency characteristics of the discharge signal, the time domain signal is decomposed into multiple scales by using wavelet transform technology; the setting of the warning threshold is a reasonable cable discharge interval set according to the historical data and operating conditions of the cable.

[0014] In this embodiment, the acoustic wave signal acquisition process of the acoustic wave probe at the cable joint in step S1 comprises the following steps; S11. Clean and dry the cable test site to eliminate the influence of surface dirt and moisture on the test results; S12. Aim the ultrasonic probe at the cable connector to be tested and apply a pressure of 3-5 kg ​​to ensure effective transmission of the sound wave signal.

[0015] By applying pressure to the cable connector to be tested through an ultrasonic probe, close contact between the two can be ensured, thereby improving the accuracy of the test data.

[0016] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A cable partial discharge collection method, characterized in that: The following steps are involved: S1: Use a fixing device to fix multiple ultrasonic probes in a circular array near the cable joint. After installation, ensure the installation temperature of the cable joint to be tested, and then use a temperature control device to perform temperature compensation on the ultrasonic probe. After temperature compensation, use an acoustic wave probe to collect acoustic wave signals at multiple locations at the cable joint; S2: After data collection, the weak signal received from the ultrasonic probe is amplified by a signal amplifier, and the measured signal is preprocessed after amplification. After preprocessing, singular value measurement is used for quantization combined with CEEMDAN threshold layered denoising; S3: After noise removal, the filtered signal is subjected to spectrum analysis to identify the frequency characteristics of the discharge signal, and then the artificial intelligence algorithm is used to compare historical data with real-time data to identify different discharge modes; S4: After identifying the discharge pattern, the time-frequency characteristics of the discharge signal are extracted, and then analyzed by the PRPD module to further quantify the intensity and regularity of the discharge activity. After analysis, the PRPD module transmits the data to the display screen in the form of waveform graphs and spectrum graphs to visually display the change trend of the discharge signal, and stores the data in the data storage device for archiving. In this way, the collection can be completed and compared with the warning threshold after collection. Once abnormal discharge is detected, an alarm is immediately triggered.

2. A cable partial discharge collection method according to claim 1, characterized in that: The process of collecting the acoustic signal of the acoustic wave probe at the cable joint in step S1 comprises the following steps; S11. Clean and dry the cable test site to eliminate the influence of surface dirt and moisture on the test results; S12. Aim the ultrasonic probe at the cable connector to be tested and apply a pressure of 3-5 kg ​​to ensure effective transmission of the sound wave signal.

3. A cable partial discharge collection method according to claim 1, characterized in that: In step S1, the fixing device may be a clamp or a bracket. After installation, ensure that the ultrasonic probe is stable and does not shake.

4. A cable partial discharge collection method according to claim 1, characterized in that: In step S1, the ultrasonic probe uses a piezoelectric ceramic sensor and a magnetostrictive sensor.

5. A cable partial discharge collection method according to claim 1, characterized in that: The pre-processing in step S2 is to remove background noise and other interference signals by using a bandpass filter, and only retain the specific frequency components related to the partial discharge.

6. A cable partial discharge collection method according to claim 1, characterized in that: In step S3, the artificial intelligence algorithm can use CNN or RNN. Before use, the historical cable discharge characteristics are input into the artificial intelligence algorithm to train and verify the artificial intelligence algorithm.

7. A cable partial discharge collection method according to claim 1, characterized in that: In step S4, when extracting the time-frequency characteristics of the discharge signal, the time domain signal is decomposed into multiple scales by using wavelet transform technology.

8. A cable partial discharge collection method according to claim 1, characterized in that: The setting of the warning threshold in step S4 is a cable discharge interval that is reasonably set based on the historical data and operating conditions of the cable.