Partial Discharge Detection System for Gas Insulated Switchgear

Abstract

The present invention provides a partial discharge detection system for a gas-insulated switchgear, which mainly relates to the technical field of partial discharge detection of power equipment. The partial discharge detection system for the gas-insulated switchgear comprises: an ultrasonic detection device, comprising a plurality of ultrasonic sensors, the ultrasonic sensors being configured to be attached to the bottom of the circuit breaker air chamber of the gas-insulated switchgear, and the ultrasonic detection device being used to collect ultrasonic signals; an ultra-high frequency detection device, comprising an ultra-high frequency sensor, the ultra-high frequency sensor being configured to be arranged inside the tank of the gas-insulated switchgear, and the ultra-high frequency detection device being used to collect electromagnetic wave signals; a processing device, which is configured to be connected to the ultrasonic detection device and the ultra-high frequency detection device respectively, and the processing device being used to perform partial discharge detection based on the electromagnetic wave signal and the ultrasonic signal to obtain partial discharge detection results.

Description

Technical Field

[0001] The present invention relates to the technical field of partial discharge detection of electric power equipment, and more specifically, to a partial discharge detection system of a gas insulated switchgear. Background Art

[0002] Gas Insulation Switchgear (GIS) has been widely used in power systems due to its high safety, small footprint, long maintenance cycle and excellent arc extinguishing performance. However, during the manufacturing, transportation, installation and opening and closing operations of GIS, metal particles inevitably enter the circuit breaker gas chamber. Once the metal particles contact or approach the surface of the insulator, flashover faults may occur.

[0003] At present, GIS equipment operating on site usually uses ultra-high frequency (UHF) sensors to monitor partial discharge in the gas chamber. However, metal particles tend to remain stationary under the normal operating voltage of GIS, and the amount of partial discharge generated is extremely low, which makes it difficult for UHF sensors to capture their existence. In addition, the high-frequency overvoltage generated when the disconnector is operated will generate high-frequency electromagnetic waves similar to partial discharge signals. These electromagnetic waves are very likely to overlap with the detection frequency band of the UHF sensor, resulting in false alarms. At the same time, relying solely on acoustic signals cannot fully reflect the frequency of partial discharge caused by metal particles and the severity of the discharge. Summary of the invention

[0004] In view of this, the present invention provides a partial discharge detection system for a gas insulated switchgear.

[0005] One aspect of the present invention provides a partial discharge detection system for a gas insulated switchgear, comprising: an ultrasonic detection device, comprising a plurality of ultrasonic sensors, the ultrasonic sensors being configured to be attached to the bottom of a circuit breaker gas chamber of the gas insulated switchgear, the ultrasonic detection device being used to collect ultrasonic signals; an ultra-high frequency detection device, comprising an ultra-high frequency sensor, the ultra-high frequency sensor being configured to be arranged inside a tank of the gas insulated switchgear, the ultra-high frequency detection device being used to collect electromagnetic wave signals; a processing device, being configured to be connected to the ultrasonic detection device and the ultra-high frequency detection device, respectively, the processing device being used to perform partial discharge detection based on the electromagnetic wave signal and the ultrasonic signal to obtain partial discharge detection results.

[0006] According to an embodiment of the present invention, the ultrasonic detection equipment also includes an ultrasonic sensing optical path structure and an ultrasonic signal detector, and the ultrasonic sensing optical path structure is configured to connect the multiple ultrasonic sensors and the ultrasonic signal detector; wherein the multiple ultrasonic sensors are used to collect and obtain multiple initial ultrasonic signals; the ultrasonic sensing optical path structure is used to generate multiple beat frequency signals based on the multiple initial ultrasonic signals; and the ultrasonic signal detector is used to demodulate the multiple beat frequency signals to obtain the ultrasonic signal.

[0007] According to an embodiment of the present invention, the ultrasonic sensing optical path structure includes a laser, an isolator, a first coupler, an acousto-optic effect unit, a delay optical fiber, a second coupler, a plurality of third couplers, a plurality of photodetectors, a fourth coupler, a plurality of optical fiber circulators and a plurality of Faraday rotators; wherein the laser is used to generate a reference optical signal and a detection optical signal via the isolator and the first coupler, the reference optical signal is configured to be input to the second coupler via the acousto-optic effect unit and the delay optical fiber, and the detection optical signal is configured to be input to the fourth coupler; the second coupler is used to divide the reference optical signal into multiple reference photon signals, and the reference photon signal is configured to be input to the first input end of the third coupler; The fourth coupler is used to divide the above-mentioned detection light signal into multiple first detection photon signals, and the above-mentioned first detection photon signal is configured to be input into the above-mentioned ultrasonic sensor through the above-mentioned optical fiber circulator; the above-mentioned ultrasonic sensor is used to perform acoustic signal modulation on the above-mentioned first detection photon signal based on the collected initial ultrasonic signal to obtain a second detection photon signal, and the above-mentioned second detection photon signal is configured to be reflected by the above-mentioned Faraday rotator and then input into the second input end of the above-mentioned third coupler through the above-mentioned optical fiber circulator; the above-mentioned third coupler is used to couple the above-mentioned reference photon signal and the above-mentioned second detection photon signal to the above-mentioned photoelectric detector; the above-mentioned photoelectric detector is used to obtain the above-mentioned beat frequency signal based on photoelectric detection of the above-mentioned reference photon signal and the above-mentioned second detection photon signal.

[0008] According to an embodiment of the present invention, the ultrasonic signal detector includes a data acquisition card and multiple ultrasonic signal processing units; wherein the ultrasonic signal processing units are used to sequentially amplify, demodulate and filter the beat frequency signals to obtain demodulated signals; and the data acquisition card is used to obtain the ultrasonic signals based on the demodulated signals output by each of the ultrasonic signal processing units.

[0009] According to an embodiment of the present invention, the above-mentioned UHF detection equipment also includes a voltage limiter, a coaxial cable and an UHF signal detector; wherein the above-mentioned voltage limiter is configured to be arranged inside the tank body of the above-mentioned gas insulated switchgear, and the above-mentioned voltage limiter is configured to be connected to the above-mentioned UHF sensor, and the above-mentioned voltage limiter is used to clamp the initial electromagnetic wave signal collected by the above-mentioned UHF sensor to obtain a first electromagnetic wave signal; the above-mentioned coaxial cable is configured to pass through the tank body of the above-mentioned gas insulated switchgear, and the above-mentioned coaxial cable is configured to be respectively connected to the above-mentioned voltage limiter and the above-mentioned UHF signal detector, and the above-mentioned coaxial cable is used to transmit the above-mentioned first electromagnetic wave signal to the above-mentioned UHF signal detector; the above-mentioned UHF signal detector is used to perform envelope detection processing on the above-mentioned first electromagnetic wave signal to obtain the above-mentioned electromagnetic wave signal.

[0010] According to an embodiment of the present invention, the above-mentioned coaxial cable includes a cable and a double-layer shielding structure wrapping the above-mentioned cable, the outer shielding structure of the above-mentioned double-layer shielding structure is copper braiding or copper foil, and the inner shielding structure of the above-mentioned double-layer shielding structure is copper braiding or copper foil.

[0011] According to an embodiment of the present invention, the ultrasonic sensor includes a core shaft and a single-mode bend-sensitive optical fiber wound around the core shaft.

[0012] According to an embodiment of the present invention, the above-mentioned UHF sensor is a circular discoidal antenna.

[0013] According to an embodiment of the present invention, the processing device is configured to: for any one of the electromagnetic wave signal and the ultrasonic signal, perform smoothing on the first sensor signal to obtain a second sensor signal; perform cross-correlation operation on the second sensor signal and a standard partial discharge signal corresponding to the second sensor signal to obtain a cross-correlation operation result; and obtain the partial discharge detection result based on the cross-correlation operation results of the electromagnetic wave signal and the ultrasonic signal.

[0014] According to an embodiment of the present invention, the processing device is further configured to: in the case where the local discharge detection result indicates that a local discharge event has occurred, based on the voltage amplitudes of the electromagnetic wave signal and the ultrasonic signal, normalize the second sensor signal to obtain a third sensor signal; based on a signal threshold, count the pulses of the third sensor signal to obtain the number of pulses; based on the third sensor signal and the number of pulses, obtain a risk coefficient; based on the risk coefficients of the electromagnetic wave signal and the ultrasonic signal, obtain a risk assessment result of the local discharge event.

[0015] According to the embodiment of the present invention, through the joint detection of ultrasonic detection equipment and ultra-high frequency detection equipment, under the high-frequency overvoltage excitation generated by the operation of the disconnector, the collected acoustic signal and electromagnetic signal are jointly evaluated to achieve efficient capture of weak partial discharge signals, thereby achieving accurate positioning and risk analysis of partial discharge caused by metal particles in the gas-insulated switchgear. Among them, the ultrasonic sensor arranged at the bottom of the circuit breaker air chamber of the gas-insulated switchgear can effectively capture the ultrasonic signal of the movement of metal particles, combined with the high-frequency electromagnetic signal of partial discharge detected by the ultra-high frequency sensor arranged inside the tank of the gas-insulated switchgear, to achieve comprehensive monitoring of the movement of metal particles and partial discharge events. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0017] Figure 1 A schematic diagram of a partial discharge detection system for a gas insulated switchgear according to an embodiment of the present invention is shown.

[0018] Figure 2 A schematic diagram of an ultrasonic detection device according to a specific embodiment of the present invention is shown.

[0019] Figure 3 A schematic diagram of an ultrasonic sensor according to a specific embodiment of the present invention is shown.

[0020] Figure 4 A schematic diagram of a UHF detection device according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0021] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0022] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0023] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0024] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0025] Gas Insulation Switchgear (GIS) has been widely used in power systems due to its high safety, small footprint, long maintenance cycle and excellent arc extinguishing performance.

[0026] During the manufacturing, transportation, installation and opening and closing operations of GIS, metal particles inevitably enter the circuit breaker gas chamber. These metal particles may be stationary at the bottom of the GIS shell or adsorbed on the surface of the insulator, and usually do not cause partial discharge under stable operating conditions. However, for a period of time after the disconnector completes the closing operation, due to the slow movement of the contacts and the lack of arc extinguishing ability, the high-frequency operating overvoltage generated will stimulate the metal particles in the gas chamber to move. Once the metal particles contact or approach the surface of the insulator, the local electric field strength will be concentrated, forming a weak point of insulation, which may eventually cause a flashover fault. This phenomenon poses a serious threat to the safe operation of GIS.

[0027] Currently, GIS equipment operating on site usually uses ultra-high frequency (UHF) sensors to monitor partial discharge in the gas chamber. However, metal particles tend to remain stationary under the normal operating voltage of GIS, and the amount of partial discharge generated is extremely low, which makes it difficult for UHF sensors to capture their existence. In addition, the high-frequency overvoltage generated when the disconnector is operated will generate high-frequency electromagnetic waves similar to partial discharge signals. These electromagnetic waves are very likely to overlap with the detection frequency band of the UHF sensor, resulting in false alarms. Therefore, traditional UHF detection technology has limitations when dealing with such complex working conditions, and it is difficult to effectively distinguish high-frequency overvoltage signals from real discharge signals.

[0028] Ultrasonic detection technology has significant advantages in detecting the movement of metal particles because it can capture the acoustic signals generated by the movement of metal particles. In particular, under high-frequency overvoltage excitation, the movement of metal particles produces obvious acoustic signals. However, relying solely on acoustic signals cannot fully reflect the frequency of partial discharge caused by metal particles and the severity of the discharge.

[0029] In view of this, the embodiment of the present invention realizes efficient capture of weak partial discharge signals by joint detection of ultrasonic detection equipment and ultra-high frequency detection equipment under the high-frequency overvoltage excitation generated by the operation of the disconnector, and then realizes accurate positioning and risk analysis of partial discharge caused by metal particles in the gas-insulated switchgear. Among them, the ultrasonic sensor arranged at the bottom of the circuit breaker air chamber of the gas-insulated switchgear can effectively capture the ultrasonic signal of the movement of metal particles, and combined with the high-frequency electromagnetic signal of partial discharge detected by the ultra-high frequency sensor arranged inside the tank of the gas-insulated switchgear, it realizes comprehensive monitoring of the movement of metal particles and partial discharge events.

[0030] Specifically, an embodiment of the present invention provides a partial discharge detection system for a gas insulated switchgear, comprising: an ultrasonic detection device, comprising a plurality of ultrasonic sensors, the ultrasonic sensors being configured to be attached to the bottom of a circuit breaker air chamber of the gas insulated switchgear, the ultrasonic detection device being used to collect ultrasonic signals; an ultra-high frequency detection device, comprising an ultra-high frequency sensor, the ultra-high frequency sensor being configured to be arranged inside a tank body of the gas insulated switchgear, the ultra-high frequency detection device being used to collect electromagnetic wave signals; a processing device, being configured to be connected to the ultrasonic detection device and the ultra-high frequency detection device, respectively, the processing device being used to perform partial discharge detection based on the electromagnetic wave signal and the ultrasonic signal to obtain a partial discharge detection result.

[0031] Figure 1 A schematic diagram of a partial discharge detection system for a gas insulated switchgear according to an embodiment of the present invention is shown.

[0032] like Figure 1 As shown, the partial discharge detection system includes an ultrasonic detection device 1 , a UHF detection device 2 and a processing device 3 .

[0033] Among them, the ultrasonic detection equipment 1 includes multiple ultrasonic sensors, and the multiple ultrasonic sensors can be configured on the outside of the gas-insulated switchgear, so that the multiple ultrasonic sensors can use the shell of the gas-insulated switchgear as a transmission medium to monitor the movement of metal particles inside it. The multiple ultrasonic sensors receive the sound wave vibrations generated by discharge or the movement of metal particles and convert them into ultrasonic signals.

[0034] Preferably, a plurality of ultrasonic sensors may be attached to the bottom of the circuit breaker air chamber of the gas insulated switchgear, so that the ultrasonic sensors can directly capture ultrasonic signals caused by the movement of metal particles while avoiding any interference with the normal operation of the gas insulated switchgear.

[0035] For example, a plurality of ultrasonic sensors can be firmly attached to the bottom of the circuit breaker air chamber of the gas-insulated switchgear by magnetic attraction.

[0036] The UHF detection device 2 includes a UHF sensor, which can be arranged inside the tank of the gas-insulated switchgear to ensure that the high-frequency electromagnetic wave signal generated by the partial discharge event can be captured. The high-frequency electromagnetic wave signal can be used to provide detailed information of the discharge event, such as the discharge location, type and intensity.

[0037] The processing device 3 is connected to the ultrasonic detection device 1 and the ultra-high frequency detection device 2 through a dedicated interface to ensure real-time transmission and synchronous processing of data. The processing device 3 can perform comprehensive analysis and processing on the received ultrasonic signal and ultra-high frequency electromagnetic wave signal based on the detection algorithm, and generate partial discharge detection results according to the analysis results. The partial discharge detection results can be used to distinguish the discharge signal from the background noise to identify the location, type, intensity and time of occurrence of the discharge, so as to achieve effective evaluation and risk judgment of partial discharge caused by metal particles inside the gas-insulated switchgear.

[0038] Based on this, the embodiment of the present invention realizes efficient capture of weak partial discharge signals by joint detection of ultrasonic detection equipment and ultra-high frequency detection equipment under the high-frequency overvoltage excitation generated by the operation of the disconnector, and then realizes accurate positioning and risk analysis of partial discharge caused by metal particles in the gas-insulated switchgear. Among them, the ultrasonic sensor arranged at the bottom of the circuit breaker air chamber of the gas-insulated switchgear can effectively capture the ultrasonic signal of the movement of metal particles, and combined with the high-frequency electromagnetic signal of partial discharge detected by the ultra-high frequency sensor arranged inside the tank of the gas-insulated switchgear, it realizes comprehensive monitoring of the movement of metal particles and partial discharge events.

[0039] According to an embodiment of the present invention, the ultrasonic detection device 1 further includes an ultrasonic sensing optical path structure and an ultrasonic signal detector.

[0040] According to an embodiment of the present invention, the ultrasonic sensing optical path structure is configured to connect multiple ultrasonic sensors and ultrasonic signal detectors. The ultrasonic sensing optical path structure can be used to generate multiple beat frequency signals based on multiple initial ultrasonic signals collected by multiple ultrasonic sensors.

[0041] Among them, when multiple ultrasonic sensors collect the initial ultrasonic signal inside the GIS equipment, the initial ultrasonic signal can modulate the optical signal using the acousto-optic effect. The modulated optical signal will meet and interfere with the unmodulated reference optical signal at a certain point in the optical path. Since the modulated optical signal carries the frequency information of the ultrasonic signal, and the reference optical signal maintains a constant frequency, the optical signal generated by the interference will contain two components of different frequencies: one is the frequency of the reference optical signal, and the other is the frequency introduced by the ultrasonic signal in the modulated optical signal. When these two components with similar frequencies are superimposed, a beat frequency signal will be generated.

[0042] According to an embodiment of the present invention, the ultrasonic signal detector is used to demodulate a plurality of beat frequency signals generated by the ultrasonic sensing optical path structure, thereby restoring the original ultrasonic signal.

[0043] Figure 2 A schematic diagram of an ultrasonic detection device according to a specific embodiment of the present invention is shown.

[0044] like Figure 2 As shown, the ultrasonic sensing optical path structure includes a laser 101, an isolator 102, a first coupler 103, an acousto-optic effect driving unit 104, an acousto-optic effect unit 105, a delay optical fiber 106, a second coupler 107, a plurality of third couplers 108, a plurality of photodetectors 109, a fourth coupler 110, a plurality of optical fiber circulators 111, a plurality of ultrasonic sensors 112 and a plurality of Faraday rotators 113.

[0045] In this embodiment, the laser 101 is used as a light source to generate a stable optical signal. The laser 101 is connected to the isolator 102. The optical signal emitted by the laser 101 is divided into two paths after passing through the isolator 102 and the first coupler 103, one path being used as a reference optical signal and the other path being used as a detection optical signal. Preferably, the laser 101 can provide a narrow line width laser output as the light source of the entire system to reduce the phase noise of the optical signal and improve the detection accuracy.

[0046] In this embodiment, the isolator 102 is connected to the first coupler 103 . The isolator 102 can be used to ensure unidirectional transmission of the optical signal and prevent the reflected light from interfering with the laser 101 .

[0047] In this embodiment, the first coupler 103 is connected to the acousto-optic effect unit 105 , and the first coupler 103 can be used to divide the optical signal emitted by the laser 101 into a reference optical signal and a detection optical signal, and input the reference optical signal to the acousto-optic effect unit 105 .

[0048] In this embodiment, the acousto-optic effect unit 105 is respectively connected to the acousto-optic effect driving unit 104 and the delay optical fiber 106. The acousto-optic effect unit 105 can utilize the acousto-optic effect to modulate the reference optical signal based on the acoustic wave to change the frequency, phase or amplitude of the optical wave. For example, the reference optical signal can be modulated to generate a 200 MHz optical signal.

[0049] In this embodiment, the delay optical fiber 106 is connected to the second coupler 107 , wherein the delay optical fiber 106 can be used to delay the reference optical signal to match the path length of the detection optical signal.

[0050] In this embodiment, the second coupler 107 is connected to the plurality of third couplers 108 respectively. The second coupler 107 can be used to split the reference optical signal into multiple reference photon signals, which are input to the first input ends of the plurality of third couplers 108 respectively.

[0051] In this embodiment, the first coupler 103 may also be connected to the fourth coupler 110 , and the first coupler 103 may be used to input the detection light signal to the fourth coupler 110 .

[0052] In this embodiment, the plurality of fourth couplers 110 are respectively connected to the plurality of optical fiber circulators 111 , and the plurality of fourth couplers 110 can be used to divide the detection light signal into a plurality of first detection photon signals, which are respectively input into the plurality of optical fiber circulators 111 .

[0053] In this embodiment, multiple fiber circulators 111 are connected to multiple Faraday rotators 113 via ultrasonic sensors 112, wherein multiple fiber circulators 111 can be used to guide the first detection photon signal to be transmitted on a specific path, ensuring that the first detection photon signal can sequentially pass through the ultrasonic sensor 112 and the Faraday rotator 113. The fiber circulator 111 can be a 150 nm fiber circulator.

[0054] The multiple Faraday rotators 113 reflect the second detection photon signal and change its polarization direction to ensure that the optical signal can smoothly return to the optical fiber circulator 111 and the third coupler 108 .

[0055] In this embodiment, the plurality of third couplers 108 are respectively connected to the plurality of photodetectors 109 , and the plurality of third couplers 108 can be used to couple the reference photon signal and the second detection photon signal to form interference signals which are input to the plurality of photodetectors 109 .

[0056] In this embodiment, the plurality of photodetectors 109 may obtain a beat frequency signal based on photodetection of the reference photon signal and the second detection photon signal.

[0057] In this embodiment, the ultrasonic signal detector includes a plurality of ultrasonic signal processing units 114 and a data acquisition card 115. The input ends of the plurality of ultrasonic signal processing units 114 are respectively connected to the output ends of the plurality of photodetectors 109, and the output ends of the plurality of ultrasonic signal processing units 114 are connected to the data acquisition card 115. The plurality of ultrasonic signal processing units 114 can be used to sequentially amplify, demodulate and filter the beat frequency signal to obtain a demodulated signal.

[0058] In this embodiment, the plurality of ultrasonic signal processing units 114 may adopt a dual-channel demodulation amplifier, specifically, the dual-channel demodulation amplifier may include a charge amplifier, a demodulation circuit and a filter. Among them, the charge amplifier may be used to amplify the beat frequency signal and enhance its strength, for example, it may be amplified 100 times to ensure that the signal strength is high enough while avoiding excessive amplification and introducing noise. Among them, the demodulation circuit may be used to extract the phase change of the ultrasonic signal from the amplified signal. For example, a differential cross multiplication algorithm (DCM) may be used to extract phase information by calculating the differential and cross multiplication of the signal. The demodulated signal may be used to reflect the sound pressure amplitude of the external ultrasonic signal. Among them, the filter may be used to filter the demodulated signal to remove unnecessary noise and interference. The frequency range of the filter may be configured to be within 200kHz to retain the ultrasonic signal associated with the movement of metal particles while filtering out high-frequency noise and low-frequency interference.

[0059] In this embodiment, the data acquisition card 115 is connected to the processing device 3, wherein the data acquisition card 115 can obtain the ultrasonic signals detected by each ultrasonic sensor 112 based on the demodulation signals output by each of the multiple ultrasonic signal processing units 114, thereby realizing real-time synchronous measurement of multi-channel ultrasonic signals.

[0060] In this embodiment, the ultrasonic sensor 112 may be used to perform acoustic signal modulation on the first detection photon signal to obtain a second detection photon signal.

[0061] Figure 3 A schematic diagram of an ultrasonic sensor according to a specific embodiment of the present invention is shown.

[0062] like Figure 3 As shown, the ultrasonic sensor can be formed by winding a sensing optical fiber on a core shaft. The sensing optical fiber can be configured as a single-mode bend-sensitive optical fiber, and the core shaft can be configured as an aluminum core shaft, wherein the radius of the aluminum core shaft can be configured as 20 mm, and the height can be configured as 40 mm. The length of the single-mode bend-sensitive optical fiber can be configured as 50 m.

[0063] When metal particles move near the ultrasonic sensor, ultrasonic waves are generated, which propagate to the aluminum core shaft and the single-mode bend-sensitive optical fiber tightly wound on it. Due to the high sensitivity of single-mode bend-sensitive optical fiber to bending changes, when ultrasonic waves act on the core shaft, it causes a tiny bend in the optical fiber. This bending causes the optical signal inside the optical fiber to change in phase or intensity. By detecting these changes, the ultrasonic sensor can accurately capture the tiny ultrasonic signals generated by the movement of metal particles and convert the ultrasonic waves into electrical signals for subsequent processing and analysis.

[0064] Figure 4 A schematic diagram of a UHF detection device according to a specific embodiment of the present invention is shown.

[0065] like Figure 4 As shown, the UHF detection device 2 may include a UHF sensor 201 , a voltage limiter 202 , a coaxial cable 203 and a UHF signal detector 204 .

[0066] In this embodiment, the UHF sensor 201 can use a circular disc-cone antenna with a diameter of 50 mm. The antenna can cover a bandwidth of 100 MHz to 3 GHz, and its gain can be configured to 11 dBi and the standing wave ratio can be configured to 1.2 to ensure that various high-frequency electromagnetic wave signals generated by local discharge inside the GIS can be captured.

[0067] In this embodiment, the voltage limiter 202 may be disposed inside the tank of the gas insulated switchgear, and the voltage limiter 202 may be configured to be connected to the UHF sensor 201. The voltage limiter 202 may be used to clamp the initial electromagnetic wave signal collected by the UHF sensor 201 to obtain a first electromagnetic wave signal, so as to protect the system from overvoltage damage and ensure that the signal is stably transmitted to the UHF signal detector 204.

[0068] The voltage limiter 202 can be made of solid silicon material to clamp excessive voltage signals by utilizing its nonlinear voltage-current characteristics. The fast response time of the voltage limiter 202 can be configured to be less than 1ns to ensure that when partial discharge occurs inside the gas-insulated switchgear, the generated high voltage signal will not cause damage to the subsequent ultra-high frequency signal detector 204 and data processing unit. The operating voltage of the voltage limiter 202 can be configured to be 5V, and the clamping voltage can be configured to be 5V±0.5V. These configurations enable the voltage limiter 202 to effectively protect the system, prevent equipment damage or data distortion caused by overvoltage, and improve the stability and safety of the system.

[0069] In this embodiment, the coaxial cable 203 can pass through the tank body of the gas insulated switchgear. The coaxial cable 203 is respectively connected to the voltage limiter 202 and the UHF signal detector 204. The coaxial cable 203 can be used to transmit the first electromagnetic wave signal to the UHF signal detector 204.

[0070] The coaxial cable 203 may be a double-shielded coaxial cable, including a double-layer shielding structure of a cable and a wrapped cable, wherein the inner and outer shielding materials of the double-layer shielding structure may be configured as copper braid or copper foil materials to collaboratively provide additional shielding protection. The cable length may be configured to be no more than 10 m to reduce signal attenuation. The double-shielded coaxial cable may be used as a transmission medium to effectively resist external electromagnetic interference and ensure signal integrity and accuracy.

[0071] The frequency range of the coaxial cable 203 can be configured to be 300MHz to 3GHz. Within this frequency range, the attenuation of the cable is less than 3dB / m to ensure the integrity and accuracy of the signal. A seal can be provided at the connection between the coaxial cable 203 and the tank body, and the seal can be, for example, a flange. The connector type of the coaxial cable 203 connected to the voltage limiter 202 and the UHF signal detector 204 can be configured to be SMA type or N type to ensure good compatibility.

[0072] In this embodiment, the UHF signal detector 204 can be connected to the processing device 3, and the UHF signal detector 204 can be used to perform envelope detection processing on the first electromagnetic wave signal to obtain an electromagnetic wave signal, and transmit the electromagnetic wave signal to the processing device 3 for real-time monitoring and analysis, thereby achieving an accurate assessment of the hazard of metal particles inside the gas-insulated switchgear.

[0073] The UHF signal detector 204 can use a Schottky diode to perform envelope detection processing on the first electromagnetic wave signal, and the operating frequency range of the UHF signal detector 204 can be configured to be 100 MHz to 3 GHz, the gain can be configured to be 20 dB ± 2 dB, the noise factor can be configured to be less than 3 dB, and the dynamic range can be configured to be greater than 80 dB. These parameters can ensure that the UHF signal detector 204 can accurately extract the high-frequency electromagnetic wave signal generated by partial discharge and convert it into an electrical signal that can be used for data analysis.

[0074] According to an embodiment of the present invention, the processing device is configured to smooth the first sensing signal of any one of the electromagnetic wave signal and the ultrasonic signal to obtain a second sensing signal; perform cross-correlation operation on the second sensing signal and a standard partial discharge signal corresponding to the second sensing signal to obtain a cross-correlation operation result; and obtain a partial discharge detection result based on the respective cross-correlation operation results of the electromagnetic wave signal and the ultrasonic signal.

[0075] According to an embodiment of the present invention, the first sensing signal may be used to characterize any sensing signal of an electromagnetic wave signal and an ultrasonic signal.

[0076] According to an embodiment of the present invention, the collected electromagnetic wave signals and ultrasonic signals may be preprocessed to ensure the consistency and reliability of the data. The preprocessing method may include smoothing processing and outlier processing.

[0077] According to a specific embodiment of the present invention, outlier processing can be performed on the collected electromagnetic wave signals and ultrasonic signals based on statistical threshold judgment, filtering methods based on signal characteristics (such as median filtering, Kalman filtering, etc.), etc., so as to identify and remove outliers in the signals. The outliers in the electromagnetic wave signals and ultrasonic signals may include extreme data points caused by sensor failure, electromagnetic interference, etc.

[0078] According to a specific embodiment of the present invention, a moving average method may be used to perform weighted averaging on each data point in the first sensing signal and the data points around it, thereby obtaining a smoothed signal and using it as the second sensing signal.

[0079] For example, a moving window size can be set, and the moving window size can be determined based on the number of data points involved in the average, and then the window is moved in sequence, and the data points in each window are averaged to obtain the second sensor signal. Specifically, the second sensor signal is calculated as follows:

[0080] (1);

[0081] In the formula, represents the second sensor signal, N represents the number of moving windows, i represents the moving window sequence number, and t represents time. Represents the first sensor signal.

[0082] According to an embodiment of the present invention, a cross-correlation operation can be performed on the second sensing signal and the standard partial discharge signal corresponding to the second sensing signal to identify whether the second sensing signal (for example, a signal after smoothing) contains features similar to the standard partial discharge signal, thereby determining whether a partial discharge event exists. Each ultrasonic signal and each electromagnetic wave signal corresponds to a standard partial discharge signal. Specifically, the calculation method of the cross-correlation operation result is as follows:

[0083] (2);

[0084] In the formula, represents the result of cross-correlation operation, Represents the standard partial discharge signal, Indicates time delay.

[0085] According to an embodiment of the present invention, a peak value and an average value are extracted from the cross-correlation operation result, wherein the peak value of the cross-correlation operation result can be used to represent the correlation at the time delay where the two signals are most similar, and the average value of the cross-correlation operation result can be used to represent the overall correlation level.

[0086] According to an embodiment of the present invention, based on the peak value of the cross-correlation operation result and the average value of the cross-correlation operation result, a ratio result of the peak value to the average value is calculated, and the ratio result can be used to measure the similarity and consistency of the signal as a partial discharge detection result. Specifically, the calculation method of the ratio result of the peak value to the average value is as follows:

[0087] (3);

[0088] In the formula, R max Represents the peak value of the cross-correlation operation result, R ave represents the average value of the cross-correlation operation results, and H represents the ratio result.

[0089] According to an embodiment of the present invention, a danger threshold can be set, which can be determined based on experimental data, equipment characteristics and experience to distinguish between partial discharge signals and interference signals. When the ratio result exceeds the set danger threshold, it can be considered that the second sensor signal contains features similar to the standard partial discharge signal, so the second sensor signal can be determined as a partial discharge signal. When the ratio result is lower than the danger threshold, it is considered that the second sensor signal is not similar enough to the standard partial discharge waveform, so the second sensor signal is determined as an interference signal.

[0090] Based on this, the embodiment of the present invention conducts a quantitative assessment of the intensity and impact range of partial discharge through comprehensive analysis of multi-sensor signals. The set danger threshold enables the system to timely determine whether the discharge signal is a partial discharge signal or an interference signal, thereby reducing the risk of false alarms and missed alarms. This accurate risk assessment provides an important guarantee for the safe operation of the equipment.

[0091] According to an embodiment of the present invention, the processing device is further configured to: when the local discharge detection result indicates that a local discharge event has occurred, based on the respective voltage amplitudes of the electromagnetic wave signal and the ultrasonic signal, normalize the second sensor signal to obtain a third sensor signal; based on the signal threshold, count the pulses of the third sensor signal to obtain the number of pulses; based on the third sensor signal and the number of pulses, obtain a risk coefficient; based on the third sensor signal and the number of pulses, obtain a risk assessment result of the local discharge event based on the respective risk coefficients of the electromagnetic wave signal and the ultrasonic signal.

[0092] According to an embodiment of the present invention, in partial discharge detection, since different sensors have different sensitivities, response characteristics and measurement ranges, the voltage amplitudes detected by them may be very different. Such differences will bring difficulties to subsequent data analysis and comparison. In order to eliminate such differences and improve the comparability and accuracy of data, the voltage amplitudes detected by the ultrasonic sensor and the UHF sensor can be normalized.

[0093] Specifically, before normalization, a reference partial discharge amount can be selected. This reference partial discharge amount can be determined based on experimental data, equipment characteristics and industry standards to represent a typical partial discharge amount so as to unify the data of different sensors to a standard scale. For example, 10pC can be selected as the reference partial discharge amount.

[0094] In this specific embodiment, for the UHF sensor and the ultrasonic sensor, based on the reference partial discharge amount, the voltage amplitudes of the electromagnetic wave signal and the ultrasonic signal corresponding to the reference partial discharge amount are determined respectively and used as the reference voltage amplitude.

[0095] In this specific embodiment, after the reference voltage is determined, the actual voltage amplitudes of the electromagnetic wave signal and the ultrasonic signal are measured by the UHF sensor and the ultrasonic sensor.

[0096] In this specific embodiment, normalization is performed on the actual voltage amplitudes of the electromagnetic wave signal and the ultrasonic signal to convert the actually measured voltage amplitude into a ratio relative to the reference partial discharge amount. The normalized voltage amplitude can be used as the third sensing signal, and the calculation method is as follows:

[0097] (4);

[0098] (5);

[0099] In the formula, represents the voltage amplitude of the normalized UHF signal, represents the voltage amplitude of the normalized ultrasonic signal, Indicates the actual voltage amplitude of the UHF signal, Indicates the reference voltage amplitude of the UHF signal, Represents the actual voltage amplitude of the ultrasonic signal, Indicates the reference voltage amplitude of the ultrasonic signal.

[0100] In this specific embodiment, the normalized voltage amplitude can be used to represent the ratio of the current partial discharge amount to the reference partial discharge amount. This process ensures the comparability of data from different sensors and facilitates the correspondence between the signal amplitude and the severity of the discharge amount.

[0101] Based on this, the embodiments of the present invention can ensure that the data collected from different sensors can be compared and analyzed under a unified standard through normalization processing. This not only improves the comparability and accuracy of the data, but also facilitates subsequent data processing and analysis. For example, when evaluating the severity of a partial discharge event, the normalized voltage values ​​can be directly compared without considering the differences between sensors. In addition, the normalization process also helps to reduce false positives and false negatives caused by different sensor characteristics, and improves the accuracy and reliability of detection.

[0102] According to an embodiment of the present invention, after the second sensing signal is normalized, the number of discharge pulses can be identified and counted from the normalized local discharge signal based on a pulse number extraction method to evaluate the local discharge activity frequency, which is further used to reflect the activity level of discharge events caused by metal particles inside the GIS.

[0103] Specifically, a signal threshold may be set to process the normalized voltage signal, that is, the third sensing signal, wherein the signal threshold may be set as a multiple of the reference discharge amount, and the specific expression is as follows:

[0104] (6);

[0105] In the formula, represents the signal threshold, k represents the multiple set according to the noise level and detection sensitivity, where k can be set to 1. Represents the third sensor signal.

[0106] In this specific embodiment, a signal peak value exceeding the signal threshold is determined as a valid partial discharge pulse.

[0107] In this specific embodiment, for the UHF sensor and the ultrasonic sensor, the pulse numbers of the UHF signal and the ultrasonic signal in each third sensing signal are extracted respectively. These pulse numbers reflect the frequency of local discharge activity during the detection period, so as to effectively evaluate the frequency of local discharge events and provide a data basis for subsequent risk analysis.

[0108] In this specific embodiment, the third sensing signal is multiplied by the pulse number to obtain a risk coefficient. The risk coefficient can be used to evaluate the risk of a partial discharge event. Specifically, the coefficient can comprehensively reflect the intensity and frequency of the partial discharge and serve as an important parameter for risk analysis. The risk coefficient is calculated as follows:

[0109] (7);

[0110] (8);

[0111] In the formula, represents the risk factor of UHF signal, represents the risk factor of the ultrasound signal, Indicates the number of pulses of the UHF signal, Indicates the pulse number of the ultrasonic signal.

[0112] In this specific embodiment, a higher value of the risk coefficient indicates that the intensity and frequency of partial discharge are greater, and the potential risk of the equipment is also higher.

[0113] According to the embodiments of the present invention, based on the risk coefficients of the electromagnetic wave signal and the ultrasonic signal, a joint risk analysis can be performed to intuitively and quickly determine the risk level of the partial discharge event and obtain a risk assessment result of the partial discharge event.

[0114] Specifically, the risk factors of ultrasonic sensors and UHF sensors can be comprehensively evaluated by constructing a two-dimensional coordinate table. In the two-dimensional coordinate table, the horizontal axis and the vertical axis represent the risk factors of ultrasonic sensors and UHF sensors, respectively. By mapping these risk factors into the two-dimensional table, the risk level of partial discharge events can be quickly determined.

[0115] In this specific embodiment, the risk level can be divided into four levels: low risk, medium risk, high risk and extremely high risk.

[0116] Table 1

[0117]

[0118] As shown in Table 1, the risk factor of UHF signal Less than 100, and the risk factor of the ultrasound signal When it is less than 5, the hazard level is low. For the low-risk level, the risk factors of both sensors are low, indicating that the partial discharge activity is less and the intensity is low, and there will be no obvious threat to the GIS equipment in the short term.

[0119] As shown in Table 1, the risk factor of UHF signal Greater than 100, and the risk factor of the ultrasound signal If the risk factor is less than 5, the risk level is medium. Less than 100, and the risk factor of the ultrasound signal If the value is greater than 5 and less than 50, the risk level is medium. Less than 10, and the risk factor of the ultrasound signal When the value is greater than 50, the hazard level is medium. For medium-risk levels, partial discharge is more frequent and more intense, requiring in-depth inspection and preventive maintenance to avoid further development of faults.

[0120] As shown in Table 1, the risk factor of UHF signal Greater than 100, and the risk factor of the ultrasound signal If the value is greater than 5 and less than 50, the risk level is high. Less than 100 and greater than 10, risk factor of ultrasound signal When the value is greater than 50, the hazard level is high. For high-risk levels, the frequency and intensity of partial discharge events are at a high level, the equipment may face a greater risk of failure, and maintenance measures need to be taken as soon as possible.

[0121] As shown in Table 1, the risk factor of UHF signal Greater than 100, and the risk factor of the ultrasound signal When the value is greater than 50, the hazard level is extremely high. For extremely high hazard levels, the discharge phenomenon is very serious and the equipment is at great risk of failure. It must be shut down immediately and fully inspected and repaired.

[0122] Based on this, the embodiments of the present invention construct a two-dimensional coordinate table and perform a joint hazard analysis combining the data from ultrasonic and UHF sensors. This can intuitively and quickly assess the severity of local discharge events caused by metal particles inside GIS equipment and provide a scientific basis for subsequent fault warnings and equipment maintenance.

[0123] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention may be combined and / or combined in various ways. All of these combinations and / or combinations fall within the scope of the present invention.

[0124] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A partial discharge detection system for a gas insulated switchgear, characterized in that: The partial discharge detection system comprises: An ultrasonic detection device, comprising a plurality of ultrasonic sensors, wherein the ultrasonic sensors are configured to be attached to the bottom of a circuit breaker gas chamber of a gas insulated switchgear, and the ultrasonic detection device is used to collect and obtain ultrasonic signals; A UHF detection device, comprising a UHF sensor, wherein the UHF sensor is configured to be disposed inside the tank of the gas insulated switchgear, and the UHF detection device is used to collect electromagnetic wave signals; a processing device, configured to be connected to the ultrasonic detection device and the UHF detection device respectively, the processing device being used to perform partial discharge detection based on the electromagnetic wave signal and the ultrasonic signal to obtain a partial discharge detection result; The ultrasonic sensor includes a core shaft, and a single-mode bend-sensitive optical fiber wound around the core shaft, the core shaft is configured as an aluminum core shaft, the radius of the aluminum core shaft is configured as 20 mm, the height is configured as 40 mm, and the length of the single-mode bend-sensitive optical fiber is configured as 50 m, wherein the ultrasonic sensor is configured as follows: when the ultrasonic wave generated by the metal particles moving near the ultrasonic sensor is propagated to the aluminum core shaft and the single-mode bend-sensitive optical fiber, based on the high sensitivity of the single-mode bend-sensitive optical fiber to bending changes, when the ultrasonic wave acts on the core shaft, a slight bend of the single-mode bend-sensitive optical fiber is caused, thereby causing a phase change or an intensity change of an optical signal inside the single-mode bend-sensitive optical fiber, so that the ultrasonic sensor captures the slight ultrasonic signal generated by the movement of the metal particles; The UHF detection device further includes a voltage limiter, a coaxial cable and a UHF signal detector, wherein the UHF sensor is a circular disc-cone antenna, the diameter of the circular disc-cone antenna is configured to be 50 mm, the gain is configured to be 11 dBi, and the standing wave ratio is configured to be 1.2; The voltage limiter is configured to be arranged inside the tank of the gas insulated switchgear, the voltage limiter is configured to be connected to the ultra-high frequency sensor, and the voltage limiter is used to clamp the initial electromagnetic wave signal collected by the ultra-high frequency sensor to obtain a first electromagnetic wave signal, wherein the voltage limiter adopts solid silicon material to clamp the high voltage signal by utilizing the nonlinear voltage-current characteristics of the solid silicon material, the fast response time of the voltage limiter is configured to be less than 1ns, the working voltage of the voltage limiter is configured to be 5V, and the clamping voltage is configured to be 5V±0.5V; The coaxial cable is configured to penetrate the tank body of the gas insulated switchgear, the coaxial cable is configured to connect the voltage limiter and the ultra-high frequency signal detector respectively, and the coaxial cable is used to transmit the first electromagnetic wave signal to the ultra-high frequency signal detector, wherein the frequency range of the coaxial cable is configured to be 300 MHz to 3 GHz, and the attenuation of the coaxial cable is configured to be less than 3 dB / m; The UHF signal detector is used to perform envelope detection processing on the first electromagnetic wave signal to obtain the electromagnetic wave signal, wherein the UHF signal detector adopts a Schottky diode, the operating frequency range of the UHF signal detector is configured to be 100 MHz to 3 GHz, the gain of the UHF signal detector is configured to be 20 dB±2 dB, the noise coefficient of the UHF signal detector is configured to be less than 3 dB, and the dynamic range of the UHF signal detector is configured to be greater than 80 dB.

2. The partial discharge detection system according to claim 1, characterized in that: The ultrasonic detection device further comprises an ultrasonic sensing optical path structure and an ultrasonic signal detector, wherein the ultrasonic sensing optical path structure is configured to connect the plurality of ultrasonic sensors and the ultrasonic signal detector; Wherein, the multiple ultrasonic sensors are used to collect and obtain multiple initial ultrasonic signals; The ultrasonic sensing optical path structure is used to generate a plurality of beat frequency signals based on the plurality of initial ultrasonic signals; The ultrasonic signal detector is used to demodulate the multiple beat frequency signals to obtain the ultrasonic signal.

3. The partial discharge detection system according to claim 2, characterized in that: The ultrasonic sensing optical path structure includes a laser, an isolator, a first coupler, an acousto-optic effect unit, a delay optical fiber, a second coupler, a plurality of third couplers, a plurality of photodetectors, a fourth coupler, a plurality of optical fiber circulators and a plurality of Faraday rotators; The laser is used to generate a reference light signal and a detection light signal via the isolator and the first coupler, the reference light signal is configured to be input to the second coupler via the acousto-optic effect unit and the delay optical fiber, and the detection light signal is configured to be input to the fourth coupler; The second coupler is used to divide the reference optical signal into multiple reference photon signals, and the reference photon signals are configured to be input to the first input end of the third coupler; The fourth coupler is used to divide the detection light signal into a plurality of first detection photon signals, and the first detection photon signals are configured to be input to the ultrasonic sensor through the optical fiber circulator; The ultrasonic sensor is used to perform acoustic signal modulation on the first detection photon signal based on the collected initial ultrasonic signal to obtain a second detection photon signal, and the second detection photon signal is configured to be input to the second input end of the third coupler through the optical fiber circulator after being reflected by the Faraday rotator; The third coupler is used to couple the reference photon signal and the second detection photon signal to the photodetector; The photodetector is used to obtain the beat frequency signal based on photodetection of the reference photon signal and the second detection photon signal.

4. The partial discharge detection system according to claim 2, characterized in that: The ultrasonic signal detector includes a data acquisition card and a plurality of ultrasonic signal processing units; The ultrasonic signal processing unit is used to sequentially amplify, demodulate and filter the beat frequency signal to obtain a demodulated signal; The data acquisition card is used to obtain the ultrasonic signal based on the demodulated signals output by each of the ultrasonic signal processing units.

5. The partial discharge detection system according to claim 1, characterized in that: The coaxial cable comprises a cable and a double-layer shielding structure wrapping the cable, wherein the outer shielding structure of the double-layer shielding structure is copper braiding or copper foil, and the inner shielding structure of the double-layer shielding structure is copper braiding or copper foil.

6. The partial discharge detection system according to claim 1, characterized in that: The processing device is configured to: For any one of the first sensing signals of the electromagnetic wave signal and the ultrasonic signal, smoothing the first sensing signal to obtain a second sensing signal; Performing a cross-correlation operation on the second sensor signal and a standard partial discharge signal corresponding to the second sensor signal to obtain a cross-correlation operation result; The partial discharge detection result is obtained based on the cross-correlation operation results of the electromagnetic wave signal and the ultrasonic signal.

7. The partial discharge detection system according to claim 6, characterized in that: The processing device is further configured to: When the partial discharge detection result indicates that a partial discharge event has occurred, normalizing the second sensing signal based on respective voltage amplitudes of the electromagnetic wave signal and the ultrasonic signal to obtain a third sensing signal; Based on the signal threshold, counting the pulses of the third sensor signal to obtain the number of pulses; Obtaining a risk coefficient based on the third sensing signal and the number of pulses; Based on the risk coefficients of the electromagnetic wave signal and the ultrasonic signal, a risk assessment result of the partial discharge event is obtained.

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