Non-intrusive monitoring system and method for internal pressure in arcing process of oil-immersed mutual inductor based on sound wave information

Abstract

The invention relates to the field of high-voltage tests of power equipment, and discloses a non-intrusive monitoring system and method for internal pressure in the arcing process of an oil-immersed mutual inductor based on sound wave information, and the system comprises a pulse signal generator, and the pulse signal output end of the pulse signal generator is connected with an ultrasonic transmitting probe. An ultrasonic receiving probe used for receiving ultrasonic signals is arranged at the position opposite to the ultrasonic transmitting probe, the ultrasonic receiving probe is connected to a data acquisition card, the data card is connected to a data processing unit, and the data processing unit can obtain pressure information in the oil-immersed transformer according to data output by the data acquisition card. According to the invention, a non-intrusive detection method can be adopted to detect the pressure change condition in the testing process of the mutual inductor, the equipment structure is not damaged, and the reliability of the testing result is ensured; the ultrasonic sensing probe is arranged outside the mutual inductor and is not influenced by strong electromagnetic interference of electric arc generated in equipment during testing.

Description

Technical Field

[0001] The invention relates to the field of high-voltage testing of electric power equipment, and in particular to a non-intrusive monitoring system and method for the internal pressure of an oil-immersed mutual inductor during an arcing process based on acoustic wave information. Background Art

[0002] When a serious arc fault occurs inside an oil-immersed transformer, the transformer oil inside the tank will crack rapidly in a short period of time under the action of the high-temperature arc, producing a large amount of mixed gases such as hydrocarbons, hydrogen, and carbon dioxide, causing the internal pressure of the tank to rise sharply. Under the action of internal pressure, the tank body will undergo a certain degree of elastic or even plastic deformation. When the local stress exceeds the strength limit of the tank material, the tank will rupture, causing a combustion and explosion accident, resulting in serious economic losses. Therefore, it is urgent to carry out internal arc tests on oil-immersed power equipment and accurately detect the changes in the internal pressure of the transformer equipment during the arcing process, so as to complete the effective evaluation of the reliability and safety of the oil-immersed transformer under arc faults and ensure the safe and stable operation of power equipment.

[0003] Conventional pressure test instruments need to punch holes in the transformer shell so that the pressure sensor can directly contact the internal liquid to complete the pressure measurement. However, during the transformer arc test, if a hole is punched in its shell, it will lead to structural weaknesses, causing the shell of the equipment to burst under internal pressure. Therefore, it is urgent to study a non-invasive oil-immersed transformer internal pressure detection technology to provide key technical support for oil-immersed transformer arc test evaluation. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a non-intrusive monitoring system and method for the internal pressure of an oil-immersed transformer during arcing based on acoustic wave information. The present invention does not require drilling holes in the transformer housing to measure the internal pressure of the transformer housing.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A non-intrusive monitoring system for the internal pressure of an oil-immersed transformer during an arcing process based on acoustic wave information comprises a pulse signal generator, a pulse signal output end of the pulse signal generator is connected to an ultrasonic transmitting probe, an ultrasonic receiving probe is provided at a position opposite to the ultrasonic transmitting probe for receiving the ultrasonic signal emitted by the output end of the ultrasonic transmitting probe, the ultrasonic receiving probe is connected to a data acquisition card, the data card is connected to a data processing unit, and the data processing unit can obtain pressure information in the oil-immersed transformer according to data output by the data acquisition card.

[0006] Preferably, the pulse signal output terminal of the pulse signal generator is also connected to the external trigger interface of the data acquisition card to trigger the clock of the data acquisition card to reset to zero.

[0007] Preferably, the data processing unit includes a fiber optic data transmitting module, a fiber optic data receiving module and a computing unit connected in sequence, the fiber optic data transmitting module is used to convert the electrical signal output by the data acquisition card into an optical signal, the fiber optic data receiving module is used to convert the optical signal output by the fiber optic data transmitting module into an electrical signal, and the computing unit can obtain the pressure information in the oil-immersed transformer according to the optical signal output by the fiber optic data receiving module.

[0008] The present invention also provides a non-intrusive monitoring method for the internal pressure of an oil-immersed transformer during arcing based on acoustic information. The monitoring method is performed using the monitoring system of the present invention as described above. The detection method includes: An ultrasonic transmitting probe is arranged on the shell of the transformer sample to be tested, and an ultrasonic receiving probe is arranged on the other side of the shell of the transformer sample to be tested, so that the ultrasonic receiving probe is directly opposite to the ultrasonic transmitting probe; The ultrasonic transmitting probe is stimulated by a pulse signal generator to emit a pulse ultrasonic signal, the ultrasonic receiving probe receives the pulse ultrasonic signal emitted by the ultrasonic transmitting probe, the data acquisition card acquires the waveform of the pulse ultrasonic signal received by the ultrasonic receiving probe, and the data processing unit obtains the pressure information in the oil-immersed transformer according to the waveform of the pulse ultrasonic signal acquired by the data acquisition card.

[0009] Preferably, the repetition period T of the periodic pulses emitted by the pulse signal generator satisfies the following relationship:

[0010] Where, L is the diameter of the transformer sample under test, c 0 is the sound velocity of the transformer oil of the tested transformer sample at normal temperature and pressure.

[0011] Preferably, the pulse width of the periodic pulse emitted by the pulse signal generator satisfies the following relationship:

[0012] Where, L is the diameter of the transformer sample housing under test, c 0 is the sound velocity of the transformer oil of the tested transformer sample at normal temperature and pressure.

[0013] Preferably, the pressure in the transformer sample under test is P The speed of sound c Satisfies the following relationship: c = f ( P ) In the formula, P is the internal pressure of the transformer sample under test, cis the speed of sound at that pressure.

[0014] Preferably, the pressure in the transformer sample under test is P The speed of sound c The calibration methods include: Transformer oil is filled in a cylindrical pressure vessel, and ultrasonic transmitting and receiving probes are placed on both sides of the pressure vessel. By applying different pressures to the pressure vessel, the sound velocity in the transformer oil under the corresponding pressure conditions is measured, the change law of the sound velocity is analyzed and tested, and a calibration curve between the sound velocity and pressure is established. The pressure information in the oil-immersed transformer can be obtained through the calibration curve between the sound velocity and pressure.

[0015] Preferably, the data acquisition card adopts a communication serial bus format.

[0016] Preferably, the analog bandwidth of the data acquisition card is not less than 150 MHz.

[0017] The present invention has the following beneficial effects: In the non-invasive monitoring system for internal pressure of the arcing process of the oil-immersed transformer based on acoustic wave information of the present invention, a pulse signal generator is used to enable an ultrasonic transmitting probe to emit a pulse ultrasonic signal, and an ultrasonic receiving probe is used to receive the pulse ultrasonic signal emitted by the ultrasonic transmitting probe. When in use, the ultrasonic transmitting probe is set on the shell of the transformer sample to be tested, and the ultrasonic receiving probe is set on the other side of the shell of the transformer sample to be tested. The ultrasonic receiving probe is directly opposite to the ultrasonic transmitting probe. The present invention uses the signal change when the pulse ultrasonic signal passes through the transformer sample to obtain the pressure information in the transformer sample to be tested, thereby providing key technical support for the arc test evaluation of the oil-immersed transformer. The present invention can use a non-invasive detection method to detect the pressure change during the transformer test, without causing damage to the equipment structure, and ensures the reliability of the test results; the ultrasonic sensor probe (i.e., the ultrasonic transmitting probe and the ultrasonic receiving probe) are arranged outside the transformer, and are not affected by the strong electromagnetic interference generated by the arc inside the equipment during the test, thereby improving the accuracy and stability of the perception of the pressure change. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall system layout of the non-intrusive monitoring system for the internal pressure of the oil-immersed transformer during the arcing process based on acoustic wave information of the present invention; Figure 2 It is a graph of ultrasonic pulse emission, receiving waveform and pressure change curve in an embodiment of the present invention.

[0019] In the figure, 1-pulse signal generator, 2-transmitting probe tail cable, 3-ultrasonic transmitting probe, 4-tested transformer sample, 5-ultrasonic receiving probe, 6-receiving probe tail cable, 7-data acquisition card, 8-signal transmission coaxial cable, 9-output USB line, 10-optical fiber data transmitting module, 11-signal transmission optical fiber, 12 optical fiber data receiving module, 13 optical fiber receiver output USB line, 14 host computer display system. DETAILED DESCRIPTION

[0020] The present invention is described clearly and completely below in conjunction with the accompanying drawings and embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, not all embodiments.

[0021] The non-intrusive monitoring system and method for the internal pressure of an oil-immersed transformer during an arcing process based on acoustic wave information provided by the present invention can perform real-time and reliable monitoring of the changes in the internal pressure of the transformer during the arcing process, and reliably transmit the signal to a control room for real-time reading and display, so as to solve the technical problem that the changes in the internal pressure of the equipment in the current transformer arc test cannot be effectively measured, and thus it is difficult to complete the evaluation of the transformer's arc resistance reliability. At the same time, it also avoids the problem that conventional pressure testing instruments need to punch holes in the transformer housing so that the pressure sensor is in direct contact with the internal liquid to complete the pressure measurement.

[0022] The exemplary embodiments of the present invention are implemented by the following technical solutions: Reference Figure 1 In the non-intrusive monitoring system for internal pressure of an oil-immersed transformer arcing process based on acoustic information of the present invention, an ultrasonic transmitting probe 3 is connected to a pulse signal generator 1 through a transmitting probe cable tail cable 2, the ultrasonic transmitting probe 3 is closely attached to the shell of a transformer sample 4 under test, and an ultrasonic receiving probe 5 is closely attached to the other side of the transformer sample 4 under test, facing the ultrasonic transmitting probe 3. The ultrasonic receiving probe 5 receives the ultrasonic signal after passing through the transformer sample 4 under test and is connected to a data acquisition card 7 through a receiving probe tail cable 6, and the data acquisition card 7 collects the ultrasonic signal received by the ultrasonic receiving probe 5. The external trigger signal of the data acquisition card 7 is connected to the pulse signal generator 1 through a signal transmission coaxial cable 8. The output USB line 9 of the data acquisition card 7 is connected to the optical fiber data transmitting module 10, and the optical fiber data transmitting module 10 converts the electrical signal collected by the data acquisition card 7 into an optical signal, and transmits it through a signal transmission optical fiber 11, and finally is received and converted into an electrical signal by an optical fiber data receiving module 12, and the electrical signal converted by the optical fiber data receiving module 12 is connected to a host computer display system 14 by an optical fiber receiver output USB line 13.

[0023] During the test, the ultrasonic transmitting probe 3 and the ultrasonic receiving probe 5 are respectively arranged on the opposite sides of the oil-immersed transformer housing, and the sound waves emitted by the ultrasonic transmitting probe 3 pass through the oil-immersed transformer and are received by the ultrasonic receiving probe 5 .

[0024] The ultrasonic transmitting probe 3 is excited by the pulse signal generator 1 to emit periodic, high-frequency pulse sound waves. In order to achieve high-performance pressure detection, the repetition period T of the periodic pulses emitted by the pulse signal generator 1 meets the following conditions:

[0025] Where L is the diameter of the transformer to be tested, c 0 is the sound velocity of transformer oil at normal temperature and pressure; The pulse width of the periodic pulse emitted by the pulse signal generator 1 T p The following conditions must be met:

[0026] The output of the pulse signal generator 1 is divided into two paths. One signal is input into the ultrasonic generating probe 3 through the transmitting probe tail cable 2 to excite periodic pulse ultrasonic waves. The other signal is input into the external trigger interface of the data acquisition card 7 through the signal transmission cable 8 to trigger the clock of the data acquisition card 7 to reset to zero.

[0027] The data acquisition card 7 collects and receives the pulsed ultrasonic waveform received by the ultrasonic probe 5, and transmits it to the host computer through the optical fiber transmission device for analysis.

[0028] The pressure monitoring principle of the above monitoring system is: the propagation speed of sound waves in the medium is related to the density of the material. When the pressure inside the transformer increases, the density of the transformer oil will change, and the propagation speed of the sound waves will also change accordingly, showing a monotonic function relationship: c = f ( P ) P is the internal pressure of the transformer, c is the speed of sound under the pressure, and the functional relationship is obtained through calibration. By analyzing the speed of sound waves transmitted inside the transformer, the pressure can be analyzed.

[0029] The transmission speed of the sound wave in the transformer oil inside the transformer can be obtained by analyzing the time it takes the ultrasonic receiving probe 5 to receive each ultrasonic pulse. The specific implementation method is as follows: the ultrasonic transmitting probe 3 and the ultrasonic receiving probe 5 are respectively placed on both sides of the transformer housing so that they are in the same radial direction. The distance between the two ultrasonic transmitting probes 3 and the ultrasonic receiving probe 5 is the diameter of the transformer. The transmitting probe transmits a repetition period of T, and the pulse width is Tp The receiving probe receives the ultrasonic pulse signals in sequence and obtains the transmission time of each pulse in the pulse sequence, which is expressed as

[0030] According to the relationship between the speed of sound waves and distance:

[0031] The corresponding speed of sound can be obtained:

[0032] Thus according to c = f ( P ) to get the corresponding pressure value:

[0033] In the formula, R For each acoustic pulse transmission time data set inside the transformer, t n represents the transmission time of the nth pulse in the pulse train, L is the sound wave transmission distance, t is the sound wave transmission time, C For each acoustic pulse transmission speed data set in the transformer, c n Indicates the transmission speed of the nth pulse in the pulse train, P In order to calculate the internal pressure data set of the transformer corresponding to each pulse transmission moment, P n It indicates the pressure value inside the transformer when the nth pulse in the pulse train is transmitted inside the transformer.

[0034] Said c = f ( P ) is as follows: transformer oil is filled into a cylindrical pressure vessel, and an ultrasonic transmitting probe 3 and an ultrasonic receiving probe 5 are placed on both sides of the pressure vessel respectively. By applying different pressures to the pressure vessel, the sound velocity in the transformer oil under the corresponding pressure conditions is measured, the variation law of the sound velocity is analyzed and tested, and a calibration curve between the sound velocity and pressure is established.

[0035] Considering that the high-voltage test hall and the control room are generally far apart, the signal transmission should adopt digital transmission, and the high and low voltage insulation isolation should be completed to ensure the insulation safety in the control room. The present invention proposes to use an optical fiber data transmission system to complete the signal transmission of the ultrasonic receiving probe output signal to the control room host computer, as well as the control of the acquisition system in the test hall. The specific implementation method is: when the sensor signal is transmitted, the output voltage signal of the ultrasonic receiving probe 5 is collected and converted into a digital signal by the data acquisition card 7. The data acquisition card 7 adopts the communication serial bus format and transmits the data to the optical fiber data transmitting module 10 through USB. The optical fiber data transmitting module 10 converts the digital signal into an optical digital signal and transmits it to the light data receiving module 12 in the control room along the signal transmission optical fiber. Preferably, the present invention adopts the data acquisition card 7 analog bandwidth not less than 150MHz to ensure the broadband acquisition of the vibration signal, the communication bandwidth of the two optical fiber communication modules is not less than 500 MHz, and the transmission optical fiber length is greater than 1 km. The optical fiber receiver end transmits the received signal to the host computer for display, data processing and analysis. The optical fiber receiver can also send a control signal to the sensor system on the host computer to control the start and stop of the system acquisition.

[0036] This embodiment detects the internal pressure signal of a 220 kV oil-immersed current transformer during the arcing process. The ultrasonic transmitting probe 3 is connected to the pulse signal generator 1 through the transmitting probe tail cable 2. The ultrasonic transmitting probe 3 is closely attached to the shell of the transformer sample 4 under test, and the ultrasonic receiving probe 5 is closely attached to the other side of the transformer 4 under test, facing the ultrasonic transmitting probe 3. The ultrasonic receiving probe 5 receives the ultrasonic signal and connects it to the data acquisition card 7 through the receiving probe tail cable 6 for collection. The external trigger signal of the data acquisition card 7 is connected to the pulse signal generator 1 through the signal transmission coaxial cable 7. The data acquisition card 7 outputs a USB line 9 to connect to the optical fiber data transmitting module 10, and the optical fiber data transmitting module 10 converts the electrical signal of the data acquisition card into an optical signal, and transmits it through the transmission optical fiber 11, which is preferably received by the optical fiber data receiving module 12, converted into an electrical signal, and output by the optical fiber receiver. The USB line 13 is connected to the upper computer display system 14.

[0037] In this embodiment, the repetition period of the pulse signal generated by the pulse signal generator 1 is , the pulse signal width adopts In this embodiment, the diameter of the transformer is 500 mm, so the repetition of the pulse signal is 0.4 ms and the width of the pulse signal is 0.004 ms.

[0038] The pulse waveform of the pulse signal generator 1 and the ultrasonic receiving probe 5 and the pressure change curve are displayed in the upper computer display system 14 as shown in FIG. Figure 2As shown. Since the excitation source of the ultrasonic transmitting probe 3 is the pulse signal generator 1, and the output signal frequencies of the two are the same, the waveform of the pulse signal generator 1 can be regarded as the ultrasonic input waveform. When no arc is generated inside the transformer, the internal pressure does not change, and the time interval between the ultrasonic input pulse and the output pulse remains constant; after an arc is generated inside the transformer, the transformer oil is cracked to produce a mixed gas, causing the pressure inside the transformer to change, and the sound speed therein also changes, and the time interval between the ultrasonic input pulse and the output pulse changes. According to the functional relationship between the sound speed and the pressure, a pressure change curve can be drawn.

[0039] In the above scheme of the present invention, the optical fiber communication system is used to transmit the sensing signal and send the control signal, which not only completes the high and low voltage insulation isolation, but also realizes the two-way communication of information. The operator can realize the control acquisition system acquisition in the control room and read the field test vibration data in real time without field operation, thereby avoiding danger to the operator, and can improve the anti-interference ability, so that the control accuracy is improved, and the reliability of the internal arc process record is improved.

[0040] Finally, it should be noted that the above preferred embodiments are only for illustrating the technical solutions of the present invention and are not limited thereto. For those skilled in the art, various changes such as modification, replacement or optimization can be made in terms of form and details without departing from the scope defined in the claims.

Claims

1. A non-intrusive monitoring system for internal pressure of an oil-immersed transformer during arcing based on acoustic information, characterized in that: The invention comprises a pulse signal generator (1), wherein the pulse signal output end of the pulse signal generator (1) is connected to an ultrasonic transmitting probe (3), and an ultrasonic receiving probe (5) for receiving an ultrasonic signal emitted by the output end of the ultrasonic transmitting probe (3) is provided at a position opposite to the ultrasonic transmitting probe (3), wherein the ultrasonic receiving probe (5) is connected to a data acquisition card (7), and the data card (7) is connected to a data processing unit, and the data processing unit can obtain pressure information in the oil-immersed transformer according to data output by the data acquisition card (7).

2. According to claim 1, a non-intrusive monitoring system for internal pressure of an oil-immersed transformer during arcing based on acoustic wave information, characterized in that: The pulse signal output end of the pulse signal generator (1) is also connected to the external trigger interface of the data acquisition card (7) and is used to trigger the clock of the data acquisition card (7) to reset to zero.

3. The non-intrusive monitoring system for internal pressure of an oil-immersed transformer during arcing process based on acoustic wave information according to claim 1 is characterized in that: The data processing unit comprises an optical fiber data transmitting module (8), an optical fiber data receiving module (12) and a computing unit which are connected in sequence, the optical fiber data transmitting module (8) being used to convert an electrical signal output by a data acquisition card (7) into an optical signal, the optical fiber data receiving module (12) being used to convert an optical signal output by the optical fiber data transmitting module (8) into an electrical signal, and the computing unit being capable of obtaining pressure information in the oil-immersed transformer according to the optical signal output by the optical fiber data receiving module (12).

4. A non-intrusive monitoring method for the internal pressure of an oil-immersed transformer during arcing based on acoustic information, characterized in that: The monitoring method is performed using the monitoring system according to any one of claims 1 to 3, and the detection method comprises: An ultrasonic transmitting probe (3) is arranged on the shell of the transformer sample (4) to be tested, and an ultrasonic receiving probe (5) is arranged on the other side of the shell of the transformer sample (4) to be tested, so that the ultrasonic receiving probe (5) is directly opposite to the ultrasonic transmitting probe (3); The pulse signal generator (1) excites the ultrasonic transmitting probe (3) to emit a pulse ultrasonic signal, the ultrasonic receiving probe (5) receives the pulse ultrasonic signal emitted by the ultrasonic transmitting probe (3), the data acquisition card (7) acquires the waveform of the pulse ultrasonic signal received by the ultrasonic receiving probe (5), and the data processing unit obtains the pressure information in the oil-immersed transformer according to the waveform of the pulse ultrasonic signal acquired by the data acquisition card (7).

5. The non-intrusive monitoring method for internal pressure of an oil-immersed transformer during arcing process based on acoustic wave information according to claim 4 is characterized in that: The repetition period T of the periodic pulses emitted by the pulse signal generator (1) satisfies the following relationship: Where L is the diameter of the transformer sample (4) under test, c 0 is the sound velocity of the transformer oil of the tested transformer sample (4) at normal temperature and pressure.

6. The non-intrusive monitoring method for internal pressure of an oil-immersed transformer during arcing process based on acoustic wave information according to claim 4 is characterized in that: The pulse width of the periodic pulse emitted by the pulse signal generator (1) satisfies the following relationship: Where L is the diameter of the casing of the transformer sample (4) under test, c 0 is the sound velocity of the transformer oil of the tested transformer sample (4) at normal temperature and pressure.

7. The non-intrusive monitoring method for internal pressure of an oil-immersed transformer during arcing process based on acoustic wave information according to claim 4 is characterized in that: Pressure in the transformer sample (4) under test P The speed of sound c Satisfies the following relationship: c = f ( P ) In the formula, P is the internal pressure of the transformer sample (4) under test, c is the speed of sound at that pressure.

8. The non-intrusive monitoring method for internal pressure of an oil-immersed transformer during arcing process based on acoustic wave information according to claim 4 is characterized in that: Pressure in the transformer sample (4) under test P The speed of sound c The calibration methods include: Transformer oil is filled in a cylindrical pressure vessel, and ultrasonic transmitting and receiving probes are placed on both sides of the pressure vessel. By applying different pressures to the pressure vessel, the sound velocity in the transformer oil under the corresponding pressure conditions is measured, the change law of the sound velocity is analyzed and tested, and a calibration curve between the sound velocity and pressure is established. The pressure information in the oil-immersed transformer can be obtained through the calibration curve between the sound velocity and pressure.

9. The non-intrusive monitoring method for internal pressure of an oil-immersed transformer during arcing process based on acoustic wave information according to claim 4 is characterized in that: The data acquisition card (7) adopts a communication serial bus format.

10. The non-intrusive monitoring method for internal pressure of an oil-immersed transformer during arcing process based on acoustic wave information according to claim 4, characterized in that: The analog bandwidth of the data acquisition card (7) shall not be less than 150 MHz.

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