Cable partial discharge detection device based on combined high-frequency current sensor

Abstract

The invention discloses a cable partial discharge detection device based on a combined high-frequency current sensor. The output of a low-frequency-band high-frequency current sensor is connected with the input of a signal conditioning and data acquisition unit channel 1, the output of a high-frequency-band high-frequency current sensor is connected with the input of a signal conditioning and data acquisition unit channel 2, and the output of a flexible power frequency current sensor is connected with the input of a signal conditioning and data acquisition unit channel 3. The upper computer receives a low-frequency-band high-frequency current sensor partial discharge signal, a high-frequency-band high-frequency current sensor partial discharge signal and a flexible power frequency current sensor power frequency current signal which are acquired by the signal conditioning and data acquisition unit. According to the invention, near-area partial discharge signals can be detected, far-area partial discharge signals can also be detected, the partial discharge detection capability covering a large range of a high-voltage cable line is realized, and the high-voltage cable line partial discharge detection device has important engineering practical value.

Description

Technical Field

[0001] This invention relates to the field of insulation condition detection of high-voltage cable lines, and particularly to a cable partial discharge detection device based on a combined high-frequency current sensor. Background Technology

[0002] In recent years, with the continuous development of cities and the increasing scale of power grid construction, urban power systems need to transmit electricity to every corner of the city. Therefore, the safe operation of high-voltage cable lines, especially 66kV and above high-voltage cable lines, is particularly important as a crucial piece of equipment in urban power systems. However, during the production of high-voltage cables, various latent insulation defects often occur due to raw material quality issues and improper process parameters. These defects include internal air gaps in the insulation, air gaps between the insulation and shielding layers, air gaps between the metal conductor and the shielding layer, sharp protrusions on the shielding layer, impurities in the insulation, and cracks in the insulation and shielding layers. These latent insulation defects generated during the production of high-voltage cables pose a significant challenge to the safe and reliable operation of high-voltage cable lines. On the other hand, during the laying of high-voltage cable lines, high-voltage cable terminals and joints need to be fabricated on-site. Due to non-standard on-site fabrication processes, these terminals and joints often contain latent defects, which also pose a significant challenge to the safe and reliable operation of high-voltage cable lines.

[0003] Partial discharge, as a major manifestation of latent defects in high-voltage cable lines, is both a primary cause of insulation aging and a key characteristic parameter reflecting the insulation condition. Partial discharge tests are required during the factory testing of high-voltage cables. Furthermore, commissioning tests after cable laying also require frequency-resonant synchronous partial discharge tests. Finally, during the service life of high-voltage cables, maintenance departments regularly conduct live partial discharge detection tests to accurately identify partial discharge phenomena and represent the most intuitive, ideal, and effective methods for diagnosing the insulation condition of high-voltage cables. However, since operating high-voltage cable lines are generally quite long, often reaching several kilometers, current theoretical and experimental research shows that the amplitude and bandwidth of partial discharge signals decrease with propagation distance. Therefore, traditional high-frequency current sensors used for partial discharge detection in high-voltage cables often only detect partial discharge signals close to the detection point, lacking the capability to detect signals farther away. Therefore, it is necessary to propose a cable partial discharge detection device based on a combined high-frequency current sensor, which can detect both near-field partial discharge signals and far-field partial discharge signals. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a cable partial discharge detection device based on a combined high-frequency current sensor, which can solve the problem of partial discharge detection over a large area of ​​high-voltage cable lines.

[0005] This invention includes a low-frequency high-frequency current sensor, a high-frequency high-frequency current sensor, a flexible power frequency current sensor, a signal conditioning and data acquisition unit, and a host computer. The output of the low-frequency high-frequency current sensor is connected to the input of channel 1 of the signal conditioning and data acquisition unit, the output of the high-frequency high-frequency current sensor is connected to the input of channel 2 of the signal conditioning and data acquisition unit, and the output of the flexible power frequency current sensor is connected to the input of channel 3 of the signal conditioning and data acquisition unit. The host computer receives the partial discharge signal from the low-frequency high-frequency current sensor, the partial discharge signal from the high-frequency high-frequency current sensor, and the power frequency current signal from the flexible power frequency current sensor acquired by the signal conditioning and data acquisition unit.

[0006] The output of the low-frequency high-frequency current sensor is connected to the input of channel 1 of the signal conditioning and data acquisition unit. The low-frequency cutoff frequency is 100kHz, the high-frequency cutoff frequency is 3MHz, the transmission impedance is not less than 10mV / mA, and the output impedance is 50 ohms.

[0007] The output of the high-frequency current sensor is connected to the input of channel 2 of the signal conditioning and data acquisition unit. The low-frequency cutoff frequency is 3MHz, the high-frequency cutoff frequency is 100MHz, the transmission impedance is not less than 5mV / mA, and the output impedance is 50 ohms.

[0008] The output of the flexible power frequency current sensor is connected to the input of channel 3 of the signal conditioning and data acquisition unit. The low frequency cutoff frequency is 20Hz, the high frequency cutoff frequency is 300Hz, and the maximum effective value of the measured power frequency current is not less than 3000A.

[0009] The signal conditioning and data acquisition unit has three input channels. Channel 1 connects to a low-frequency high-frequency current sensor, providing low-pass filtering, signal amplification, and data acquisition functions for the partial discharge signal from the low-frequency high-frequency current sensor. Channel 2 connects to a high-frequency high-frequency current sensor, providing low-pass filtering, signal amplification, and data acquisition functions for the partial discharge signal from the high-frequency high-frequency current sensor. Channel 3 connects to a flexible power frequency current sensor, providing low-pass filtering, shaping, and data acquisition functions for the power frequency current from the flexible power frequency current sensor.

[0010] The host computer receives the partial discharge signals from the low-frequency band high-frequency current sensor, the high-frequency band high-frequency current sensor, and the power frequency current signal from the flexible power frequency current sensor, collected by the signal conditioning and data acquisition unit. It displays the partial discharge PRPD spectrum, partial discharge pulse time-domain diagram, and partial discharge pulse time-spectrum diagram of the low-frequency band high-frequency current sensor, and the partial discharge PRPD spectrum, partial discharge pulse time-domain diagram, and partial discharge pulse time-spectrum diagram of the high-frequency band high-frequency current sensor.

[0011] By adopting the above technical solution, the present invention has the following advantages:

[0012] This invention discloses a cable partial discharge detection device based on a combined high-frequency current sensor, which enables partial discharge detection over a large section of high-voltage cable lines. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the principle of the present invention;

[0014] exist Figure 1 In the diagram, 21 is a series resonant withstand voltage device for high-voltage cable lines, 22 is an insulation joint for high-voltage cable lines, 11 is a low-frequency high-frequency current sensor, 12 is a high-frequency high-frequency current sensor, 13 is a flexible power frequency current sensor, 14 is a signal conditioning and data acquisition unit, and 15 is a host computer. Detailed Implementation

[0015] Because operating high-voltage cable lines are generally quite long, often reaching several kilometers, current theoretical and experimental research shows that the amplitude of partial discharge signals attenuates with the propagation distance during cable line transmission, and the bandwidth also decreases with the propagation distance. Traditional high-frequency current sensors used for partial discharge detection in high-voltage cables are often designed to cover a high-frequency band of 3MHz-30MHz. This means they can often only detect partial discharge signals close to the detection point, and have no detection capability for partial discharge signals farther away. However, the amplitude of partial discharge signals farther from the detection point attenuates significantly with increasing propagation distance, and their bandwidth also decreases to below 3MHz. Therefore, traditional high-frequency current sensors are unnecessary. Using a high-frequency current sensor covering the low-frequency band of 100kHz-3MHz can expand the partial discharge detection range. On the other hand, the transmission impedance of the high-frequency current sensor covering the low-frequency band of 100kHz-3MHz can be designed to be greater than that of the high-frequency current sensor covering the high-frequency band of 3MHz-100MHz, which further expands the partial discharge detection range of the high-frequency current sensor covering the low-frequency band of 100kHz-3MHz.

[0016] Referring to the accompanying drawings, the present invention comprises a low-frequency high-frequency current sensor 11, a high-frequency high-frequency current sensor 12, a flexible power frequency current sensor 13, a signal conditioning and data acquisition unit 14, and a host computer 15.

[0017] The core idea of ​​this invention, a cable partial discharge detection device based on a combined high-frequency current sensor, is that near-field partial discharge is detected by a high-frequency current sensor, while far-field partial discharge is detected by a low-frequency current sensor, ultimately achieving partial discharge detection capability covering a large section of high-voltage cable lines. Based on this principle, this invention's cable partial discharge detection device based on a combined high-frequency current sensor requires the following four components.

[0018] 1) A combined high-frequency current sensor, which consists of a low-frequency high-frequency current sensor 11 and a high-frequency high-frequency current sensor 12.

[0019] 2) The phase synchronization signal is composed of a flexible power frequency current sensor 13;

[0020] 3) A conditioning and data acquisition unit for two channels of partial discharge signals and one channel of power frequency phase synchronization signal, which is composed of signal conditioning and data acquisition unit 14;

[0021] 4) The partial discharge signal analysis unit, which is composed of the host computer 15. This invention provides a cable partial discharge detection device based on a combined high-frequency current sensor. When performing a frequency conversion resonant withstand voltage test on a high-voltage cable line, the steps for measuring the partial discharge of each large section of the high-voltage cable line can be divided into the following three steps:

[0022] 1. In the first long section of a high-voltage cable line where a variable frequency resonant voltage is applied, a cable partial discharge detection device based on a combined high-frequency current sensor can be placed at any one of the two insulating joints in this long section. First, the short-circuit wire of the insulating joint passes through the low-frequency high-frequency current sensor 11 and the high-frequency high-frequency current sensor 12. Next, the flexible power frequency current sensor 13 is sleeved on the cable body. These three sensors are then connected to the signal conditioning and data acquisition unit 14. Finally, the signal conditioning and data acquisition unit 14 is connected to the host computer 15.

[0023] 2. The series resonant withstand voltage device 21 of the high-voltage cable line applies the power frequency resonant voltage to the high-voltage cable line. At this time, the host computer 15 of the cable partial discharge detection device based on the combined high frequency current sensor can display whether there is partial discharge in this long section.

[0024] 3. Along each major section of the high-voltage cable line, install the cable partial discharge detection device based on the combined high-frequency current sensor in sequence, following step 1, to determine whether there is partial discharge in each major section of the high-voltage cable line. Reinstallation of the cable partial discharge detection device based on the combined high-frequency current sensor can be performed while the line is energized.

[0025] As can be seen, the cable partial discharge detection device based on the combined high-frequency current sensor of the present invention realizes the detection of partial discharge of each large section of the high-voltage cable line in sequence when the high-voltage cable line is under series resonant withstand voltage, realizing the partial discharge detection of long-distance high-voltage cable lines, and has important engineering practical value.

Claims

1. A cable partial discharge detection device based on a combined high-frequency current sensor, characterized in that: It includes a low-frequency band high-frequency current sensor, a high-frequency band high-frequency current sensor, a flexible industrial frequency current sensor, a signal conditioning and data acquisition unit, and a host computer; the output of the low-frequency band high-frequency current sensor is connected to the input of channel 1 of the signal conditioning and data acquisition unit, the output of the high-frequency band high-frequency current sensor is connected to the input of channel 2 of the signal conditioning and data acquisition unit, and the output of the flexible industrial frequency current sensor is connected to the input of channel 3 of the signal conditioning and data acquisition unit; the host computer receives the local discharge signal of the low-frequency band high-frequency current sensor, the local discharge signal of the high-frequency band high-frequency current sensor, and the industrial frequency current signal of the flexible industrial frequency current sensor collected by the signal conditioning and data acquisition unit.

2. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 1 is characterized in that Among them, the low-frequency cutoff frequency of the low-frequency band high-frequency current sensor is 100kHz, the high-frequency cutoff frequency is 3MHz, the transmission impedance is not less than 10mV / mA, and the output impedance is 50 ohms.

3. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 1 is characterized in that The high-frequency current sensor output in the high-frequency band is connected to the input of channel 2 of the signal conditioning and data acquisition unit. The low-frequency cutoff frequency is 3MHz, the high-frequency cutoff frequency is 100MHz, the transmission impedance is not less than 5mV / mA, and the output impedance is 50 ohms.

4. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 1 is characterized in that The output of the flexible power frequency current sensor is connected to the input of channel 3 of the signal conditioning and data acquisition unit. The low frequency cut-off frequency is 20Hz, the high frequency cut-off frequency is 300Hz, and the maximum measured power frequency current effective value is not less than 3000A.

5. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 1 is characterized in that: The signal conditioning and data acquisition unit has three channels of signal conditioning and acquisition unit input.

6. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 5 is characterized in that: Its channel 1 is connected to a low-frequency band high-frequency current sensor to realize low-pass filtering, signal amplification and data acquisition functions of the local discharge signal of the low-frequency band high-frequency current sensor.

7. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 5 is characterized in that: Its channel 2 is connected to a high-frequency current sensor in a high-frequency band to realize low-pass filtering, signal amplification and data acquisition functions of the partial discharge signal of the high-frequency current sensor in the high-frequency band.

8. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 5 is characterized in that: Channel 3 thereof is connected to a flexible industrial frequency current sensor to realize low-pass filtering, shaping and data acquisition functions of the industrial frequency current of the flexible industrial frequency current sensor.

9. The cable partial discharge detection device based on the combined high-frequency current sensor according to claim 1 is characterized in that: The host computer receives the local discharge signal of the low-frequency band high-frequency current sensor, the local discharge signal of the high-frequency band high-frequency current sensor and the power frequency current signal of the flexible power frequency current sensor collected by the signal conditioning and data acquisition unit, and displays the local discharge PRPD spectrum, local discharge pulse time domain diagram and local discharge pulse time-frequency spectrum diagram of the low-frequency band high-frequency current sensor, and displays the local discharge PRPD spectrum, local discharge pulse time domain diagram and local discharge pulse time-frequency spectrum diagram of the high-frequency band high-frequency current sensor.

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