Superposition sounder device for surface corona discharge detection of high-voltage electric appliance

Abstract

The invention relates to a superposition sounder device for surface corona discharge detection of a high-voltage electrical appliance, the device comprises an audio frequency module, a power amplifier module, a tweeter and a control module which are connected in sequence, the audio frequency module stores frequency sound data covering a surface discharge frequency band, and plays the frequency sound data according to program setting of the control module; and after the sound is amplified by the power amplifier module, a sound wave signal is actively emitted by the tweeter and is superposed with a surface corona discharge signal of the high-voltage electric appliance. Compared with the prior art, the method has the advantages of avoiding interference, timely and sensitively detecting surface corona discharge, pre-judging the insulation degradation degree and the like.

Description

Technical Field

[0001] The invention relates to the technical field of corona discharge detection along the surface of high-voltage electrical appliances, and in particular to a superimposed sounder device used for corona discharge detection along the surface of high-voltage electrical appliances. Background Art

[0002] In the power system, high-voltage electrical appliances (such as high-voltage switchgear, all-metal busbar boxes, and bushings) will experience partial discharge. The partial discharge phenomenon is the phenomenon of arc discharge or corona discharge in local areas of electrical equipment. When partial discharge occurs, it is mainly accompanied by high-frequency electromagnetic waves, ultra-high frequency electromagnetic waves, and ultrasonic waves, while emitting infrared light, ultraviolet light, and producing gases such as ozone. At present, the commonly used partial discharge live detection technologies include ultrasonic method (AE), transient earth voltage method (TEV) and ultra-high frequency method (UHF). In recent years, live detection technology based on partial discharge detection has been increasingly widely used.

[0003] However, the following deficiencies were found during the on-site partial discharge detection process:

[0004] a) External interference and weak signal: The main reason for the unsatisfactory on-site detection effect is that there are many strong electromagnetic interference sources from the outside world. It is very difficult to eliminate and prevent external electromagnetic interference by relying solely on hardware technology. At the same time, the collected signal is weak and the amplitude is very small, which is easily submerged by background noise.

[0005] b) Fully enclosed metal shielding effect: When weak local discharge occurs in switch cabinets, all-metal bus boxes and all-metal combination electrical appliances, the weak local discharge cannot be discovered and detected in time because the fully enclosed metal container has a shielding effect on electromagnetic waves.

[0006] According to IEEE standards, the frequency range of partial discharge is usually between several thousand hertz and several hundred megahertz. In electrical equipment, partial discharge will generate weak pulse currents. The frequency range of these pulse currents is wide, but mainly concentrated in the frequency band of 30kHz to 500kHz. The frequency range of high-frequency partial discharge (HFPD) is 0.2 to 2GHz, the frequency range of ultra-high frequency partial discharge (UHF PD) is 300MHz to 3GHz, and the frequency range of ultra-high frequency partial discharge (TEV PD) is 20kHz to 500MHz.

[0007] The busbar refers to the connection of various voltage distribution devices in the substation, as well as the connection between electrical equipment such as transformers and corresponding distribution devices. Its function is to connect the various current-carrying branch circuits in the substation and distribution device together, and it plays the role of collecting, distributing and transmitting electric energy. It is an important equipment in the substation.

[0008] At present, the closed busbars used in substations generally have only ordinary sealing functions, which can prevent large foreign objects from entering, but cannot effectively separate sand and dust, moisture in the outside air, and the temperature display inside the busbar box. After running for a period of time, the following faults may occur:

[0009] 1) The surface of the operating support insulator will be degraded due to the accumulation of sand and dust. Under humid or other abnormal weather conditions, external humid air will enter the box. When the bus stops running or the support insulator is cooled by radiation at night and its temperature is lower than the ambient air temperature, the surface of the support insulator will absorb moisture or condense. Condensation can easily form a fully humidified state in all parts of the support insulator. In a humid environment, the ionizable substances in the dirty layer of the dirty insulator will gradually dissolve in water. A layer of conductive water film forms on the surface of the insulator. The ionizable substances in the dirt determine the conductivity of the water film, and the insoluble substances in the dirt can play a role in absorbing moisture. This water film forms a conductive path along the surface of the insulator, allowing the leakage current to pass through the surface of the insulator, resulting in a significant reduction in the insulation performance of the busbar, and then causing partial discharge.

[0010] 2) Condensation on the partitions on the inner column wall of the common box enclosed busbar. This is because the partition is an epoxy resin board, which is mainly composed of epoxy glass fiber, and has the characteristics of non-flame retardant, hard material, and easy to absorb moisture. Especially for the partitions installed on the common wall busbar, due to the pure indoor and outdoor temperature difference, when the busbar operating conditions change, the unit is shut down or the weather changes abnormally, a large amount of condensation water will appear on the surface of the partition. Dew. This condensation seriously affects the operation of the bus. For example, in the cold winter, when the outdoor temperature is -15℃, the saturated water vapor density per cubic meter in the air is 1.73g / M3, and the temperature of the indoor switch room is usually around 20℃. The saturated water vapor density per cubic meter of indoor air is 17.28g / M3. That is to say, when the indoor and outdoor temperature difference is 35℃, 15.55 grams of water will condense per cubic meter of air on the partition surface of the A column wall in the enclosed busbar and become dew adsorbed on it. On the surface of the partition, due to the concentration of condensation water, the partition becomes the weakest point of the insulation of the entire shared box enclosed busbar. This water will seriously affect the insulation of the busbar. (The above data is from the saturated humid air table).

[0011] 3) Each phase conductor of the common box busbar has a layer of insulating paint on it, the purpose is to improve the insulation level between the conductor and the supporting insulator. However, as the service life increases, the insulating layer will gradually age or oxidize, peel off from the conductor, and cause the conductor to leak. When encountering special and special climate and environmental changes, it is easy to cause discharge short circuit accidents.

[0012] Due to dust or dirt on the surface of the supporting insulator in the box busbar, the field strength increases. When the field strength reaches the gas breakdown strength, local discharge will occur in the equipment inside the box. Among them are: Surface discharge: The solid medium used to fix and support the live parts of electrical equipment is mostly in the air. When the voltage exceeds a certain limit, discharge along the surface of the solid medium often occurs at the interface between the solid medium and the air, which is called surface discharge. Air gap discharge: During the processing of the insulating medium, due to defects in the process and materials, impurities or air gaps will exist in the insulator, forming defects in the insulating medium. Generally, the air gap is filled with air or hydrocarbon gas, and the pressure is close to atmospheric pressure. When alternating high voltage is applied externally, local and repeated breakdown will occur at the insulation defect. Corona discharge: Corona discharge often occurs in areas with high electric field strength in non-uniform electric fields. Corona discharge occurs in places where the radius of curvature of the conductor shell is small, especially at the tip, where the charge density is very large. The electric field is proportional to the charge density close to the surface of the charged body, so the field strength is very strong at the tip of the conductor. Therefore, when the potential of the conductor around the air increases, corona discharge may occur at these tips.

[0013] The signals of surface discharge and corona discharge in these partial discharges are very weak and cannot be detected by existing partial discharge detectors and other equipment.

[0014] How to achieve sensitive detection of surface corona discharge in high-voltage electrical equipment has become a technical problem that needs to be solved. Summary of the invention

[0015] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances.

[0016] The purpose of the present invention can be achieved by the following technical solutions:

[0017] According to one aspect of the present invention, there is provided a superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances, the device comprising an audio module, a power amplifier module, a tweeter and a control module connected in sequence, the audio module storing frequency sound data covering the surface discharge frequency band, actively emitting a sound wave signal through the tweeter after the sound is amplified by the power amplifier module, and superimposed with the surface corona discharge signal of the high-voltage electrical appliances, wherein the audio module plays the sound according to the program setting of the control module.

[0018] Preferably, the frequency of the device is 1K to 20KHz.

[0019] More preferably, the frequency of the device also includes multiple frequency ranges, namely 1K~6K, 5K~11K, 10K~16K and 15K~20K.

[0020] Preferably, the control module is also connected to the power amplifier module and the tweeter respectively.

[0021] Preferably, the housing of the device is made of insulating material.

[0022] Preferably, when the surface corona discharge signal is superimposed with the actively emitted sound wave signal in the same frequency band, a frequency superposition effect is generated, that is, the amplitude increases and the waveform is approximately a horizontal line.

[0023] Preferably, when the active emission sound wave signal of the same frequency band is played, the superimposed signal amplitude decreases, the frequency superposition effect is small, and the waveform of the surface corona discharge signal is restored.

[0024] Preferably, the tweeter has a sensitivity greater than 100 dB and a sound emission angle less than 30 degrees.

[0025] Preferably, the efficiency of the power amplifier module is greater than 90%, and the total harmonic distortion plus noise is less than 0.2%.

[0026] Preferably, the opening direction of the tweeter is toward the high-voltage electrical appliance under test and avoids the front of the high-voltage electrical appliance.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) The present invention uses a superposition generator device to emit audio signals near high-voltage equipment suspected of local corona discharge, which can produce a frequency superposition effect at the discharge frequency point, and produce an obvious frequency superposition effect after superimposing the originally weak local discharge, which can avoid interference frequencies and detect surface corona discharge in a timely and sensitive manner.

[0029] 2) The present invention uses multi-band sound waves to perform detection respectively to predict the degree of insulation degradation of local corona discharge. The lower the discharge frequency, the more severe the insulation degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the sound-generating part of the sound generator in the present invention;

[0031] Figure 2 It is a schematic diagram of the frequency acoustic wave characteristics of surface corona discharge in the present invention;

[0032] Figure 3 This is a schematic diagram of the superimposed frequency characteristics after emitting a 50db sound wave;

[0033] Figure 4 This is a schematic diagram of the superimposed frequency characteristics after emitting a 75db sound wave;

[0034] Figure 5 It is a schematic diagram of the structure of the superimposed sound generator device in the present invention;

[0035] Figure 6 It is a schematic diagram of the use process of the superimposed sound generator device in the present invention;

[0036] Figure 7 It is an exploded view of the components of the device of the present invention;

[0037] Figure 8 It is a schematic diagram of the waveform change after the partial discharge and the actively emitted sound wave are superimposed in the present invention;

[0038] In the attached figure, 1. OLED display screen; 2. power switch; 3. volume knob; 4. selection button; 5. upper cover; 6. charging and power amplifier board; 7. touch switch; 8. 12V battery; 9. single-chip microcomputer; 10. audio module; 11. equipment middle board; 12. tweeter; 13. outer shell; 20. power amplifier module; 30. control module. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0040] In response to the above problems, the present invention combines the "superposition principle" with partial discharge detection to indirectly measure the weak discharge in the bus box, while ensuring that the monitoring device will not affect the safe operation of the circuit breaker and the power grid. The research results have a relatively good implementation conclusion in the fully enclosed bus box, which is a new detection method.

[0041] The principle of wave superposition means that when several waves propagate in the same medium, if they meet somewhere in space, the vibration of the particle at the meeting point is the synthesis of the vibrations caused by each wave, and the displacement of the particle at any time is the vector sum of the displacements caused by each wave. After the waves meet, they still maintain their original frequency, wavelength, vibration direction and other characteristics and continue to move forward in the original propagation direction, as if they did not encounter other waves on their way. This is also called the principle of wave independence. Specifically, the waveform superposition principle shows that if there are two waveforms y1(t) and y2(t), their superposition is y(t) = y1(t) + y2(t), where y(t) is the waveform after superposition. This principle can be extended to any number of waveforms. For example, the waveform of the superposition of three waves y1(t), y2(t) and y3(t) is: y(t) = y1(t) + y2(t) + y3(t). The effect of superposition may be enhancement or cancellation, depending on the phase relationship of the waveforms.

[0042] The superposition principle of waves is an important physical principle that describes the way multiple waveforms interact with each other [3]. It has applications in many fields, such as electromagnetic wave communications, acoustics, and optics. In acoustics, the superposition principle of sound waves is used to describe the effect of multiple sound sources on the sound heard by the listener. This principle can also be applied to various types of waveforms, such as electromagnetic waves, sound waves, etc.

[0043] According to the superposition principle of sound waves, when there are two or more sound sources in space, the propagation law of the sound waves emitted by each sound source will not be changed by the existence of other sound waves. However, the fluctuation at a certain position in space is the superposition of the vibrations excited by each sound wave at that point.

[0044] This embodiment relates to a superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances, which is suitable for partial discharge detection of equipment such as 110 kV busbar boxes, high-voltage switch cabinets, and bushings. In order to ensure the safety of detection personnel and prevent static electricity transmission in the operating equipment environment, the housing of the device must be made of insulating material.

[0045] Actively emit a sound wave frequency, which is superimposed with the frequency of local corona discharge. Since the surface corona discharge frequency is mostly concentrated between 6K and 15kHz, it is necessary to actively emit a pure sound wave frequency of 1K to 20KHz. In view of the complexity and difficulty of emitting ultrasonic sound greater than 20KHz, the maximum frequency of the sound wave emitted by the present invention is less than 20KHz. The sound wave can cover the surface corona discharge frequency, and according to the sound wave superposition theory, it is superimposed with the corona discharge sound frequency signal. When working, the pure sound wave frequency of 1K to 20KHz is pre-recorded to the audio module, and then amplified by the power amplifier and played by the matching speaker.

[0046] Because the frequency of surface corona discharge is mostly concentrated between 6K and 15kHz, the maximum frequency of the sound waves superimposed by the sound generator device is about 20KHz. A tweeter that can emit clear high frequencies and has high sensitivity, low impedance and easy driving technical requirements should be selected.

[0047] For high-voltage electrical equipment such as enclosed box-type busbars, the sound-emitting part of the sound generator is required to be flat. Figure 1 This is a schematic diagram of the sound-producing part of the sound generator.

[0048] In the process of superposition effect of an actively emitted sound wave frequency and the sound wave frequency generated by local surface corona discharge, the decibel size of the actively emitted superimposed sound wave frequency has a significant impact on the amplitude effect of the superimposed frequency band. The higher the decibel, the more obvious the amplitude change of the superimposed band. Figure 2 is the frequency acoustic wave characteristic of surface corona discharge, Figure 3 The 50db superimposed frequency characteristics of the emission, Figure 4The 75db superimposed frequency characteristic of the emission is calculated as follows:

[0049] Lg(n1+Δn)>Lgn1

[0050] Where n1 is the amplitude of the surface corona discharge sound wave, in decibels, and Δn is the amplitude of the external superimposed sound, in decibels.

[0051] like Figure 5 The superimposed sound generator device includes an audio module 10, a power amplifier module 20 and a tweeter (12) connected in sequence, and also includes a control module 30 connected to the audio module 10, the power amplifier module 20, and the tweeter (12) respectively.

[0052] The audio module 10 is used to store multi-band sound data and play it according to the program setting of the control module 30. After the sound is amplified by the power amplifier module 20, it is played through the tweeter (12). The sound data stored in the audio module 10 is the frequency sound data of the surface discharge frequency band, and has the characteristic of storing the sound of the surface corona discharge frequency band with high fidelity.

[0053] The housing 13 of the device is an insulating housing. The power amplifier module 20 includes a charging and power amplifier board 6 .

[0054] The control module 30 includes a single chip microcomputer 9, which is used to control the sound playing program. The sound volume is adjusted by the sound knob 3, and the sound starts to play after the selection button 4 is pressed.

[0055] According to the above superposition amplitude decibel, because the main superposition effect is above 5KHz, the influence of low frequency on the tweeter is not considered. The decibel of the superposition sounder device requires the use of a high-power power amplifier and a high-power tweeter.

[0056] The tweeter (12) uses a 100W 8-horn, a frequency range of 1.5 to 20KHz, a sensitivity greater than 100dB, and a sounding angle less than 30 degrees to improve directivity.

[0057] The power amplifier module 20 uses a high-quality digital power amplifier board with an efficiency of >90% and a total harmonic distortion plus noise of <0.2%.

[0058] The control module 30 adopts the ESP8266 chip, the main frequency supports 80-160Mhz, supports RTOS, and integrates an onboard antenna with WI-FI MAC / BB / RF / PA / LNA.

[0059] Power consumption of the whole machine: standby 1W, maximum power 20W, powered by DC12V lithium battery.

[0060] like Figure 7The exploded diagram of the device includes an OLED display screen 1, a power switch 2, a volume knob 3, a selection button 4, an upper cover 5, a charging and power amplifier board 6, a touch switch 7, a 12V lithium battery 8; a single-chip microcomputer 9, an audio module 10, a device middle board 11, a tweeter (12), and an insulating shell 13.

[0061] The device uses multiple frequency bands for transmission. In this embodiment, five frequency bands are used for transmission: 1-6K, 5-11K, 10-16K, 15-20K and 1-20K. Due to the high-frequency sinusoidal pulse of partial discharge, the superposition sounder does not need to consider the phase of the sound wave.

[0062] The usage process of the superposition generator device is as follows Figure 6 After power-on, the timer and IO port are initialized first. After the selection button is pressed, it is determined whether multi-band switching is performed. If yes, the audio module 10 and the power amplifier module 20 are called to play the sound signal through the tweeter (12).

[0063] Benefits of multi-band settings: If a high-voltage electrical appliance has multiple partial discharges, such as dirty surface corona discharge on a 35KV high-voltage bushing, and corona discharge on multiple skirts, if a traditional partial discharge instrument is used, it can only measure the discharge index or waveform, but cannot show how many discharges there are. In contrast, this device uses multiple frequency segments for superposition testing, which can easily determine the number of discharges and the number of superposition waveforms that have occurred. Using multiple superposition frequencies to output separately, the degree of insulation degradation of local corona discharge can be predicted. Generally speaking, the lower the discharge frequency, the more severe the insulation degradation.

[0064] This embodiment also involves the application of a superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances. The project team conducted local surface corona discharge superimposed detection work at a 35 kV station.

[0065] On-site inspections revealed that a slight local discharge and surface corona discharge occurred in the middle and lower part of the porcelain bottle supporting the 35 kV B-phase bushing in the station's lead-in warehouse. On-site detection results from a partial discharge detector showed that the B-phase bushing had obvious local discharge waveforms.

[0066] The project team placed the superimposed sounder device of the present invention in front of the lead bin, with the speaker opening of the superimposed sounder device facing the inside of the station lead bin, but not directly facing it to avoid interference, such as deviating from the set angle A or set distance directly opposite the high-voltage electrical appliance under test.

[0067] First, the superimposed sounder device emits a frequency of 1K to 20K. The waveform of phase B on the partial discharge detector fluctuates significantly and becomes approximately a horizontal line. At the same time, the amplitude increases and is significantly greater than the amplitude of the unsuperimposed detection frequency. After the audio in the frequency band of the partial discharge is played, the waveform recovers. Figure 8. The detection frequency waveform of the normal A and C phases without corona discharge is a normal sine wave signal. At the same time, using a high-sensitivity full-frequency detection instrument, it is found that starting from the superimposed starting frequency, the frequency spectrum will gradually rise and fall, and near a certain frequency point, each frequency spectrum will rise and fall in sections, which is consistent with the detection results of the partial discharge detector.

[0068] Next, the superposition sounder device was used for superposition detection at four frequencies: 1K~5K, 5~10K, 10~15K, and 15~20K. It was found that the surface corona discharge frequency of the B-phase bushing in the building changed significantly after superposition in the range of 6K~8K, which was similar to the effect of a horizontal line.

[0069] Through on-site superposition detection, it was found that in a fully enclosed metal space (busbar box), when local corona discharge occurs, the sound of the same frequency band is used to produce a superposition effect, generating a superimposed audio frequency with an amplitude greater than the discharge frequency, which can be easily detected by a local discharge meter or a global audio detection instrument.

[0070] The device of the present invention can solve the problem of weak local discharge occurring in a fully enclosed metal high-voltage box-type busbar. Due to the shielding effect of the fully enclosed metal container on electromagnetic waves, the existing local discharge instrument detection cannot keenly and clearly measure the weak local discharge; and based on the existing direct local discharge detection, a new method is innovatively proposed that combines the acoustic superposition characteristics with the local discharge detection principle to obtain the characteristics of the local discharge surface insulation discharge effect, and conducts on-site measurement statistical analysis research based on theoretical verification.

[0071] In a partial discharge detection environment with severe background electromagnetic wave interference (such as near a mobile phone GPS signal transmission tower), high-frequency signals interfere with the partial discharge detector, which manifests as the partial discharge measurement of the partial discharge detector exceeding the standard, high background partial discharge measurement values, and inaccurate measurement data. After using the method of the present invention, a full-band audio signal is emitted at the suspected partial corona discharge site, which can produce a frequency superposition effect at the discharge frequency point, thereby avoiding the interference frequency and drawing an accurate abnormal discharge conclusion.

[0072] When corona discharge occurs in high-voltage electrical equipment, the location of the corona discharge cannot be accurately located. For example, in a station through-building bushing, the partial discharge detector roughly detects abnormal discharge waveforms of phases A, B, and C outside the position of the live equipment, and corona discharge occurs in the upper, middle, and lower parts of the phase B bushing, which cannot be accurately located. After using this method, full-band audio signals can be emitted on three sides of the bushing (avoiding front emission), and the partial discharge detector is used to detect and record the waveform superposition time in the fourth direction, and the location of the bushing discharge is obtained based on the waveform superposition time and intensity.

[0073] Superposition effect, weak partial discharge occurs in the fully enclosed metal high-voltage box busbar. Due to the shielding effect of the fully enclosed metal container on electromagnetic waves, when weak discharge occurs in the busbar box, the partial discharge detector cannot detect it very sensitively. After using this method, as long as the front of the busbar box is avoided, the full-band audio signal is emitted from the side and back, which can produce a frequency superposition effect at the discharge frequency point, and thus timely grasp the weak discharge in the high-voltage busbar box.

[0074] Partial discharge positioning, because the partial discharge detector passively receives partial discharge corona discharge electromagnetic waves, it cannot accurately locate the location of corona discharge when corona discharge occurs in high-voltage electrical equipment. For example, in the bushing through the building of Wangxin Station, the partial discharge detector roughly detected abnormal discharge waveforms of phases A, B, and C outside the position of the energized equipment, and corona discharge occurred in the upper, middle and lower parts of the phase B bushing, which could not be accurately located. After using this method, full-band audio signals can be emitted in multiple directions of the bushing, and the partial discharge detector can be used to detect and record the time of waveform superposition. The location of the bushing discharge can be obtained based on the location and intensity of the waveform superposition time. This method is also the first method to solve the problem that partial discharge detection cannot locate the location of corona discharge.

[0075] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances, characterized in that: The device comprises an audio module (10), a power amplifier module (20), a tweeter (12) and a control module (30) which are connected in sequence. The audio module (10) stores frequency sound data covering the frequency range of surface discharge. After the sound is amplified by the power amplifier module (20), a sound wave signal is actively emitted through the tweeter (12) to be superimposed on the surface corona discharge signal of the high-voltage electrical appliance. The audio module (10) plays the sound according to the program setting of the control module (30).

2. A superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 1, characterized in that: The frequency of the device is 1K to 20KHz.

3. A superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 2, characterized in that: The frequency of the device also includes multiple frequency sections, namely 1K~6K, 5K~11K, 10K~16K and 15K~20K.

4. A superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 1, characterized in that: The control module (30) is also connected to the power amplifier module (20) and the tweeter (12) respectively.

5. The superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 1, characterized in that: The shell of the device is made of insulating material.

6. A superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 1, characterized in that: When the surface corona discharge signal is superimposed with the actively emitted sound wave signal of the same frequency band, a frequency superposition effect is generated, that is, the amplitude increases and the waveform is approximately a horizontal line.

7. A superimposed sounder device for detecting surface corona discharge of high voltage electrical appliances according to claim 1, characterized in that: When the active emission sound wave signal in the same frequency band is finished playing, the superimposed signal amplitude decreases, the frequency superposition effect is small, and it recovers to the surface corona discharge signal waveform.

8. The superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 1, characterized in that: The tweeter (12) has a sensitivity greater than 100 dB and a sound emission angle less than 30 degrees.

9. The superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 1, characterized in that: The efficiency of the power amplifier module (20) is greater than 90%, and the total harmonic distortion plus noise is less than 0.2%.

10. The superimposed sounder device for detecting surface corona discharge of high-voltage electrical appliances according to claim 1, characterized in that: The opening direction of the tweeter (12) faces the high-voltage electrical appliance to be tested and avoids the front side of the high-voltage electrical appliance.

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