Switch cabinet partial discharge detection device and method based on pulse current and ultrahigh frequency

Abstract

The invention provides a switch cabinet partial discharge detection device and method based on pulse current and ultrahigh frequency, and belongs to the field of switch cabinet partial discharge detection. The detection device comprises an acquisition unit, an analog signal processing unit and a digital signal processing unit. The digital signal processing unit comprises a demodulation module, a digital filter, a signal mixing module and a partial discharge identification module. The acquisition unit acquires an ultrahigh frequency signal and a pulse current signal; the analog signal processing unit processes the ultrahigh frequency signal and then transmits the ultrahigh frequency signal to the demodulation module, and processes the pulse current signal and then transmits the pulse current signal to the digital filter; the demodulation module is used for performing orthogonal down-conversion on a signal and then transmitting the signal to the signal mixing module; the digital filter is used for performing passband filtering on the received signal and then transmitting the signal to the signal mixing module; the mixing module is used for fusing the two paths of signals and then transmitting the signals to the partial discharge identification module; and the partial discharge identification module is used for carrying out partial discharge identification according to the received data. According to the invention, the early partial discharge phenomenon can be detected on line.

Description

Technical Field

[0001] The invention belongs to the technical field of partial discharge detection of switch cabinets, and in particular relates to a partial discharge detection device and method for switch cabinets based on pulse current and ultra-high frequency. Background Art

[0002] High-voltage switchgear has many parts, short insulation distance, small internal space and complex structure. During long-term operation, it will fail due to factors such as electricity, heat and mechanical vibration. According to the statistical results of domestic high-voltage switchgear failure investigation, insulation failure and current-carrying failure account for 44% to 66.5% of high-voltage switchgear failures. Both of these failures are closely related to discharge and overheating.

[0003] Most of today's high-voltage switchgears are fully sealed structures. Their closed shells make it difficult for people to detect early faults with their senses. In addition, the density of internal equipment is high. Once a fault occurs, it is easy to affect nearby equipment, expand the fault, and increase the difficulty and repair cycle of repair. Moreover, as an important equipment in the operation of the power system, once a fault occurs, the high-voltage switchgear will disrupt the normal operation of the power system and have an adverse impact on the national economic production and the normal social order. Therefore, in order to ensure the operational reliability of the high-voltage switchgear, it is particularly important to perform online detection of partial discharge on the operating high-voltage switchgear. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a switch cabinet partial discharge detection device and method based on pulse current and ultra-high frequency.

[0005] In order to solve one, part or all of the above technical problems, the technical solution adopted by the present invention is: A switch cabinet partial discharge detection device based on pulse current and ultra-high frequency comprises an acquisition unit, an analog signal processing unit and a digital signal processing unit, wherein the digital signal processing unit comprises a demodulation module, a digital filter, a signal mixing module and a partial discharge identification module; the acquisition unit is used to acquire ultra-high frequency signals inside the switch cabinet and pulse current signals in the switch cabinet circuit; the analog signal processing unit is used to perform band-pass filtering, low-noise amplification and mixing processing on the acquired ultra-high frequency signals and transmit them to the demodulation module, and is used to perform high-pass filtering and gain amplification processing on the acquired pulse current signals and transmit them to the digital filter; the demodulation module is used to perform orthogonal down-conversion processing on the received signals and transmit them to the signal mixing module, and the digital filter is used to perform pass-band filtering processing on the received signals and transmit them to the signal mixing module; the mixing module is used to perform time synchronization and signal fusion on the two received signals, and transmit the fused data to the partial discharge identification module; the partial discharge identification module is used to perform partial discharge identification according to the received data.

[0006] Furthermore, the acquisition unit includes a UHF antenna for acquiring UHF signals and a high frequency current transformer for acquiring pulse current signals.

[0007] Furthermore, the analog signal processing unit includes a bandpass filter, a low noise amplifier and a mixing module for sequentially processing ultra-high frequency signals, and also includes a high-pass filter and a programmable gain amplifier for sequentially processing pulse current signals.

[0008] Furthermore, the mixing module includes an image rejection mixer and an image rejection filter, and the image rejection filter is arranged between the radio frequency input port of the image rejection mixer and the local oscillator source.

[0009] Furthermore, the mixing module also includes an anti-aliasing low-pass filter, and the anti-aliasing low-pass filter is arranged at the output end of the image rejection mixer.

[0010] Furthermore, the programmable gain amplifier is connected to an external feedback circuit, or has a built-in voltage-controlled gain function.

[0011] A switch cabinet partial discharge detection method based on pulse current and ultra-high frequency comprises: collecting ultra-high frequency signals inside the switch cabinet and pulse current signals in the switch cabinet circuit; processing the ultra-high frequency signals into a first signal through band-pass filtering, low-noise amplification and mixing, and processing the pulse current signals into a second signal through high-pass filtering and gain amplification; sampling the first signal and the second signal respectively by using independent ADC channels; performing orthogonal down-conversion processing on the sampled signal of the first signal to reduce the signal frequency to 1MHz-50MHz; performing filtering processing with a passband range of 1MHz-50MHz on the sampled signal of the second signal; performing time synchronization on the first signal subjected to down-conversion processing and the second signal subjected to filtering processing, and performing signal fusion on the two signals after time synchronization to obtain fused data; and performing partial discharge identification according to the fused data.

[0012] Furthermore, the timing synchronization method includes: performing cross-correlation calculation on two signals, and calculating the time delay according to the position of the cross-correlation peak; and performing time shift compensation on one of the signals according to the time delay to achieve timing alignment of the two signals.

[0013] Furthermore, the signal fusion method includes: allocating different weights according to the signal qualities of the two signals; and directly superimposing the two signals after multiplying them by the corresponding weights respectively.

[0014] Furthermore, the signal fusion method includes: performing time-frequency transformation on the two signals respectively to obtain the time-frequency characteristics of the two signals; using principal component analysis to perform dimensionality reduction processing on the time-frequency characteristics respectively; and performing weighted fusion on the dimensionality reduction results according to preset weights.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention utilizes a UHF antenna and a high-frequency current transformer to respectively capture the electromagnetic wave radiation and current pulse signal generated when partial discharge occurs in the switch cabinet, and has strong complementarity. When processing the UHF signal, the bandpass filter and the low-noise amplifier can effectively suppress out-of-band noise and compensate for insertion loss. The mixing module enables the signal to adapt to the sampling rate of the ADC by reducing the frequency, and the demodulation module matches the signal frequency with the current pulse signal to be fused; when processing the current pulse signal, the high-pass filter filters out the power frequency interference, the programmable gain amplifier adapts to the signal dynamic range, and the digital filter optimizes the signal quality twice. Finally, by means of signal fusion, the partial discharge characteristics of the two signals are fused, so that a higher accuracy rate will be achieved when performing partial discharge identification.

[0016] The present invention can not only detect the early partial discharge phenomenon online, but also effectively monitor the development stage of partial discharge, and provide early warning of faults for the switch cabinet. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0018] Figure 1 : A schematic structural diagram of a tool half body according to Embodiment 1 of the present invention; Among them: 100-acquisition unit, 111-UHF antenna, 121-high frequency current transformer, 200-analog signal processing unit, 211-bandpass filter, 212-low noise amplifier, 213-mixing module, 221-high pass filter, 222-programmable gain amplifier, 300-digital signal processing unit, 311-demodulation module, 321-digital filter, 331-signal mixing module, 332-partial discharge identification module. DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the content of the present invention is further clearly described below in conjunction with the embodiments and the accompanying drawings, but the protection content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0020] Example 1: See Figure 1 The purpose of this embodiment is to provide a switch cabinet partial discharge detection device based on pulse current and ultra-high frequency, including a collection unit 100, an analog signal processing unit 200 and a digital signal processing unit 300 connected in sequence.

[0021] The acquisition unit 100 includes a UHF antenna 111 and a high-frequency current transformer 121, the analog signal processing unit 200 includes a bandpass filter 211, a low-noise amplifier 212, a mixing module 213, a high-pass filter 221 and a programmable gain amplifier 222, and the digital signal processing unit 300 includes a demodulation module 311, a digital filter 321, a signal mixing module 331 and a partial discharge identification module 332.

[0022] The processing path of the UHF signal is sequentially UHF antenna 111, bandpass filter 211, mixing module 213 and demodulation module 311, and the processing path of the pulse current signal is sequentially high frequency current transformer 121, high pass filter 221, programmable gain amplifier 222 and digital filter 321. To avoid interference between the UHF signal processing path and the pulse current signal processing path, the two adopt mutually isolated grounding measures, and the analog signal processing unit 200 and the digital signal processing unit 300 also adopt mutually isolated grounding measures.

[0023] The UHF antenna 111 is arranged in the switch cabinet to collect the UHF signal generated when the switch cabinet is partially discharged; the high-frequency current transformer 121 is connected to the circuit (such as the grounding wire) of the switch cabinet to collect the pulse current signal generated when the switch cabinet is partially discharged.

[0024] The bandpass filter 211, the low noise amplifier 212 and the mixing module 213 are used to sequentially filter, amplify and mix the UHF signal collected by the UHF antenna 111, and the processed signal is transmitted to the demodulation module 311 through the ADC channel of the digital signal processing unit 300. The high-pass filter 221 and the programmable gain amplifier 222 are used to sequentially filter and amplify the pulse current signal collected by the high-frequency current transformer 121, and the processed signal is transmitted to the digital filter 321 through another ADC channel of the digital signal processing unit 300.

[0025] The demodulation module 311 performs orthogonal down-conversion processing on the received signal, and the processed signal is transmitted to the signal mixing module 331. The digital filter 321 performs secondary filtering processing on the received signal, and the processed signal is transmitted to the signal mixing module 331. The signal mixing module 331 performs time synchronization and time-frequency domain superposition processing on the two received signals, and the processed signal is transmitted to the partial discharge identification module 332; or the signal mixing module 331 performs time synchronization on the two received signals, and extracts the time-frequency features of the two signals respectively, and then performs feature fusion, and transmits the fused features to the partial discharge identification module 332. The partial discharge identification module 332 is used to identify partial discharge according to the received data.

[0026] The specifications or parameter settings of some components are as follows: The bandpass filter 211 may adopt a cavity filter, covering the ultra-high frequency range of partial discharge of the switch cabinet, with a passband range of 300MHz-1.5GHz, a center frequency of 800MHz, out-of-band suppression: not less than 40dB@200MHz and not less than 30dB@2GHz, an insertion loss of not more than 1.5dB, and a standing wave ratio of not more than 1.5:1; Low noise amplifier 212, which compensates for the loss of bandpass filter 211 and improves signal strength, has a gain of 30 dB, a bandwidth of 300 MHz-1.5 GHz, and a noise factor of no more than 1.5 dB; The mixing module 213 includes an image rejection mixer, which is used to down-convert the UHF signal to the sampling range of the adaptive ADC, with an RF input range of 300MHz-1.5GHz, and down-converting is achieved through a wide tuning local oscillator (such as 250MHz-1450MHz), and the output impedance is 50Ω; preferably, the down-converted output of the mixing module 213 is 50MHz; The high-pass filter 221 is a fourth-order active filter used to filter out power frequency and harmonic interference, with a cut-off frequency of 1MHz, a stop-band attenuation of not less than 40dB@100kHz, a pass-band fluctuation of not more than 0.5dB (1MHz-50MHz), and an impedance matching of 50Ω; Programmable gain amplifier 222, gain adjustable range 20dB-60dB, bandwidth 1MHz-50MHz; The demodulation module 311 reduces the frequency of the input signal of about 50 MHz to 1 MHz-50 MHz through digital orthogonal down-conversion; Digital filter 321, passband range 1MHz-50MHz, stopband attenuation not less than 40dB, stopband range less than 500kHz and greater than 75MHz; digital filter 321 can use 50-80 order Kaiser window FIR filter; or use 8-10 order Chebyshev II type IIR filter, and set zero phase filter compensation at the same time to avoid the influence of filter phase nonlinearity on time domain waveform; The ADC channel of the digital signal processing unit 300 has a sampling rate of not less than 150MSPS and a resolution of not less than 16 bits.

[0027] Furthermore, the mixer module 213 also includes an image suppression filter, which is arranged between the RF input port of the image suppression mixer and the local oscillator source to suppress image frequency band interference in advance. The stopband depth of the image suppression filter is not less than 50dB@200MHz.

[0028] Furthermore, the mixing module 213 also includes an anti-aliasing low-pass filter, which is arranged at the output end of the image suppression mixer to filter out high-frequency components that may remain in the signal after mixing and reduce the aliasing risk of ADC sampling; the cutoff frequency of the anti-aliasing low-pass filter is 1.05f-1.1f, where f is the output frequency of the image suppression mixer.

[0029] Furthermore, the programmable gain amplifier 222 is also connected to an external feedback circuit, or has a built-in voltage-controlled gain function, so as to achieve automatic gain control and ensure that the amplitude range of the partial discharge pulse current can be covered.

[0030] For the functional implementation of some components in this embodiment, please refer to the detection method provided in Example 2.

[0031] Embodiment 2: The purpose of this embodiment is to provide a switch cabinet partial discharge detection method based on pulse current and ultra-high frequency, which can be implemented using the detection device provided in Embodiment 1. The detection method includes: S100, collecting the UHF signal inside the switch cabinet and the pulse current signal in the switch cabinet circuit; S200, processing the ultra-high frequency signal into a first signal through band-pass filtering, low-noise amplification and mixing, and processing the pulse current signal into a second signal through high-pass filtering and gain amplification; S300, using independent ADC channels to sample the first signal and the second signal respectively; S400, performing orthogonal down-conversion processing on the sampling signal of the first signal to reduce the signal frequency to 1 MHz-50 MHz; performing filtering processing with a passband range of 1 MHz-50 MHz on the sampling signal of the second signal; S500, performing time synchronization on the processed two-way signals, and performing signal fusion on the time-synchronized signals to obtain fused data; S600: Perform partial discharge identification based on the fused data.

[0032] When the detection method is implemented by using Embodiment 1, the acquisition unit 100 is used to perform step S100, the analog signal processing unit 200 is used to perform step S200, and the digital signal processing unit 300 is used to perform steps S300-S600. The demodulation module 311 and the digital filter 321 in the digital signal processing unit 300 are used to perform step S400, the signal mixing module 331 is used to perform step S500, and the partial discharge identification module 332 is used to perform step S600.

[0033] in: The timing synchronization method in step S500 includes: S501, performing cross-correlation calculation on two signals, and calculating the time delay according to the position of the cross-correlation peak; S502, performing time shift compensation on one of the signals according to the time delay to achieve timing alignment of the two signals.

[0034] In one embodiment, the signal fusion method in step S500 includes: S511, superimposing the two signals in time and frequency domains. In another embodiment, the signal fusion method in step S500 includes: S521, extracting time and frequency features of the two signals respectively, and fusing the extracted features.

[0035] Step S511 specifically includes: allocating different weights according to the signal qualities of the two signals; and directly superimposing the two signals after multiplying them by the corresponding weights respectively.

[0036] Step S521 specifically includes: performing time-frequency transformation on the two signals respectively to obtain the time-frequency features of the two signals; performing dimensionality reduction processing on the time-frequency features respectively using the principal component analysis method; and performing weighted fusion on the dimensionality reduction results according to preset weights.

[0037] In step S600, local discharge identification based on fused data is implemented using an existing deep learning model, which will not be elaborated on or specifically limited.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A switch cabinet partial discharge detection device based on pulse current and ultra-high frequency, characterized in that: It includes an acquisition unit, an analog signal processing unit and a digital signal processing unit, wherein the digital signal processing unit includes a demodulation module, a digital filter, a signal mixing module and a partial discharge identification module; The acquisition unit is used to collect the ultra-high frequency signal inside the switch cabinet and the pulse current signal in the switch cabinet circuit; The analog signal processing unit is used to perform band-pass filtering, low-noise amplification and mixing processing on the collected ultra-high frequency signal and then transmit it to the demodulation module, and is used to perform high-pass filtering and gain amplification processing on the collected pulse current signal and then transmit it to the digital filter; The demodulation module is used to perform orthogonal down-conversion processing on the received signal and then transmit it to the signal mixing module, and the digital filter is used to perform passband filtering processing on the received signal and then transmit it to the signal mixing module; The mixing module is used to perform time synchronization and signal fusion on the two received signals, and transmit the fused data to the partial discharge identification module; the partial discharge identification module is used to perform partial discharge identification according to the received data.

2. The switch cabinet partial discharge detection device based on pulse current and ultra-high frequency according to claim 1 is characterized in that: The acquisition unit includes a UHF antenna for acquiring UHF signals and a high-frequency current transformer for acquiring pulse current signals.

3. The switch cabinet partial discharge detection device based on pulse current and ultra-high frequency according to claim 1 is characterized in that: The analog signal processing unit includes a bandpass filter, a low noise amplifier and a mixing module for sequentially processing ultra-high frequency signals, and also includes a high-pass filter and a programmable gain amplifier for sequentially processing pulse current signals.

4. The switch cabinet partial discharge detection device based on pulse current and ultra-high frequency according to claim 3 is characterized in that: The mixing module comprises an image rejection mixer and an image rejection filter, wherein the image rejection filter is arranged between a radio frequency input port of the image rejection mixer and a local oscillator source.

5. The switch cabinet partial discharge detection device based on pulse current and ultra-high frequency according to claim 4 is characterized in that: The frequency mixing module further comprises an anti-aliasing low-pass filter, and the anti-aliasing low-pass filter is arranged at the output end of the image rejection mixer.

6. The switch cabinet partial discharge detection device based on pulse current and ultra-high frequency according to claim 3 is characterized in that: The programmable gain amplifier is connected to an external feedback circuit, or has a built-in voltage-controlled gain function.

7. A switch cabinet partial discharge detection method based on pulse current and ultra-high frequency, characterized in that: include: Collect UHF signals inside the switch cabinet and pulse current signals in the switch cabinet circuit; The ultra-high frequency signal is processed into a first signal through band-pass filtering, low-noise amplification and mixing, and the pulse current signal is processed into a second signal through high-pass filtering and gain amplification; Using independent ADC channels to sample the first signal and the second signal respectively; Performing orthogonal down-conversion processing on the sampling signal of the first signal to reduce the signal frequency to 1 MHz-50 MHz; performing filtering processing with a passband range of 1 MHz-50 MHz on the sampling signal of the second signal; Performing time synchronization on the first signal processed by down-conversion and the second signal processed by filtering, and performing signal fusion on the two signals after time synchronization to obtain fused data; Partial discharge identification based on fused data.

8. The switch cabinet partial discharge detection method based on pulse current and ultra-high frequency according to claim 7 is characterized in that: The timing synchronization method includes: performing cross-correlation calculation on two signals, calculating the time delay according to the position of the cross-correlation peak; and performing time shift compensation on one of the signals according to the time delay to achieve timing alignment of the two signals.

9. The switch cabinet partial discharge detection method based on pulse current and ultra-high frequency according to claim 7 is characterized in that: The signal fusion method comprises: allocating different weights according to the signal qualities of the two signals; and directly superimposing the two signals after multiplying them by the corresponding weights respectively.

10. The switch cabinet partial discharge detection method based on pulse current and ultra-high frequency according to claim 7, characterized in that: The signal fusion method comprises: performing time-frequency transformation on two signals respectively to obtain time-frequency features of the two signals; performing dimensionality reduction processing on the time-frequency features respectively using principal component analysis; and performing weighted fusion on the dimensionality reduction results according to preset weights.

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