System, method and device for detecting vacuum bubble of vacuum on-load tap-changer

Abstract

The invention provides a system, a method and a device for detecting a vacuum bubble of a vacuum on-load tap-changer, and belongs to the field of detection of the vacuum bubble of the vacuum on-load tap-changer. The system comprises a crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photoelectric detector and an oscilloscope. Wherein the crystal sensor is arranged on the inner wall of an oil chamber of the vacuum on-load tap-changer; the voltage regulator is connected with the isolation transformer; the output end of the isolation transformer is connected to two ends of the vacuum bubble; the mains supply applies high voltage to the two ends of the vacuum bubble through the voltage regulator and the isolation transformer; the vacuum bubble, the crystal sensor and the flat ground electrode are placed in transformer oil, and a detection potential is generated after the shielding cover is pressurized; an optical fiber for detecting electric field change surrounds the crystal sensor and is connected with a laser, and the other end of the optical fiber is connected with a photoelectric detector for obtaining phase difference and an oscilloscope. The vacuum degree of the vacuum bubble can be determined through phase difference observation, and the detection accuracy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid control, and in particular to a detection system, method and device for a vacuum bubble of a vacuum on-load tap changer. Background Art

[0002] On-Load Tap Changers (OLTC) are key components of transformers. According to the arc extinguishing method, they can be divided into oil arc extinguishing and vacuum arc extinguishing. Compared with the traditional oil arc extinguishing OLTC, the arc breaking of vacuum OLTC is completed by vacuum bubble, which has the advantages of strong breaking capacity, avoiding oil pollution, long electrical and mechanical life, strong short circuit and overload resistance, etc.

[0003] The arc extinguishing ability of the vacuum bubble (vacuum interrupter) is crucial to the switching process of OLTC. During operation, the vacuum degree may be reduced due to sealing problems, mechanical damage, material degassing, etc., resulting in the inability to extinguish the arc. In severe cases, it may cause interstage short circuits and cause explosion accidents. Traditional vacuum bubble status detection relies on offline detection during regular maintenance, which has time delays and low efficiency. It is difficult to detect faults such as vacuum bubble leakage during operation in a timely manner.

[0004] Patent CN 209822553 U discloses an online monitoring device for the vacuum degree of a high-voltage vacuum circuit breaker, which solves the problem that the vacuum degree monitoring operation of the vacuum interrupter in the high-voltage vacuum circuit breaker is complicated and difficult to monitor in real time. However, when performing detection according to this technical solution, once a vacuum leak is found, the arc extinguishing ability of the vacuum bubble has been reduced. Therefore, the accuracy of the vacuum degree detection of the vacuum bubble of the vacuum on-load tap changer still needs to be further improved. Summary of the invention

[0005] The embodiments of the present invention provide a system, method and device for detecting a vacuum bubble of a vacuum on-load tap changer, so as to solve the problem that the accuracy of vacuum degree detection of the vacuum bubble of the vacuum on-load tap changer still needs to be further improved.

[0006] In a first aspect, an embodiment of the present invention provides a vacuum bubble detection system for a vacuum on-load tap changer, comprising: a crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photodetector, and an oscilloscope; Wherein, the crystal sensor is installed on the inner wall of the vacuum on-load tap changer oil chamber; One end of the voltage regulator is connected to the mains, and the other end is connected to the input end of the isolation transformer; the output end of the isolation transformer is connected to the two ends of the vacuum bubble; the mains applies high voltage to the two ends of the vacuum bubble through the voltage regulator and the isolation transformer; The flat ground electrode is connected between one end of the vacuum bubble and the isolation transformer; the vacuum bubble, the crystal sensor and the flat ground electrode are placed in transformer oil so that the shielding cover will generate a detection potential after pressurization; The crystal sensor is surrounded by an optical fiber for detecting electric field changes. One end of the optical fiber is connected to the laser, and the other end is connected to the photodetector and the oscilloscope in sequence; the photodetector and the oscilloscope are used to obtain phase difference.

[0007] In a second aspect, an embodiment of the present invention provides a method for detecting vacuum bubbles of a vacuum on-load tap changer, comprising: Obtaining structural parameters, vacuum degree and shielding cover potential of the vacuum on-load tap changer vacuum bubble; wherein the structural parameters include: contact radius, shielding cover inner diameter, distance between the shielding cover and the transformer oil tank and conductive rod length; Constructing an equivalent model of the vacuum bubble according to the structural parameters, and determining a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential; Input the detection voltage and obtain the real-time phase difference collected by the photodetector; The vacuum degree of the vacuum bubble of the vacuum on-load tap changer is determined according to the reference association relationship and the real-time phase difference.

[0008] In a third aspect, an embodiment of the present invention provides a device for detecting vacuum bubbles of a vacuum on-load tap changer, comprising: An acquisition module is used to acquire the structural parameters, vacuum degree and shielding cover potential of the vacuum bubble of the vacuum on-load tap changer; wherein the structural parameters include: contact radius, shielding cover inner diameter, distance between the shielding cover and the transformer oil tank and conductive rod length; A relationship building module, used to build an equivalent model of the vacuum bubble according to the structural parameters, and determine a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential; A detection control module is used to input a detection voltage and obtain a real-time phase difference collected by a photoelectric detector; The vacuum degree determination module is used to determine the vacuum degree of the vacuum bubble of the vacuum on-load tap changer according to the reference association relationship and the real-time phase difference.

[0009] The embodiment of the present invention provides a detection system, method and device for a vacuum bubble of a vacuum load tap changer. The detection system for the vacuum bubble of a vacuum load tap changer is constructed by a crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photodetector and an oscilloscope. The real-time monitoring of the vacuum bubble state is realized based on the crystal sensor built into the vacuum bubble. The crystal sensor is arranged on the inner wall of the oil chamber of the vacuum load tap changer. The optical fiber for detecting the change of the electric field is surrounded by the crystal sensor, and enters and exits from the elbow at the top of the oil chamber, thereby reducing the structural complexity of the detection system of the vacuum bubble of the vacuum load tap changer and improving the detection efficiency. The voltage regulator, the isolation transformer and the optical fiber cooperate to convert the electric field change of the vacuum bubble shielding cover into the detection of the optical signal, which not only realizes the amplification of the signal, improves the detection sensitivity, but also increases the anti-interference ability of the measurement signal. The embodiment of the present application can accurately determine the vacuum degree and monitor the change of the vacuum degree during the use of the vacuum bubble, take countermeasures in time before the vacuum leak occurs, and ensure the stability of the operation of the power grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 is a structural schematic diagram of a vacuum on-load tap changer provided by an embodiment of the present invention; Figure 2 1 is a schematic structural diagram of a vacuum bubble detection system for a vacuum on-load tap changer provided by an embodiment of the present invention; Figure 3 1 is a schematic structural diagram of a vacuum bubble detection system for a vacuum on-load tap changer provided by an embodiment of the present invention; Figure 4 is a flow chart of a method for detecting vacuum bubbles of a vacuum on-load tap changer provided by an embodiment of the present invention; Figure 5 The invention is a schematic structural diagram of a vacuum bubble detection device for a vacuum on-load tap changer provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0012] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0013] The vacuum degree of the vacuum bulb of the vacuum on-load tap changer is usually within the high vacuum range, generally 1.33×10 -2 -1.33×10 -5 As the service time goes by, the internal air pressure will gradually increase. Once the air pressure is higher than 1.33×10 -2 After Pa, the vacuum bubble will lose its arc extinguishing ability. The basic structure of the vacuum bubble is as follows Figure 1 As shown, it is composed of an insulating shell, a moving and static cover plate, moving and static contacts, a conductive rod, a shielding cover, and a bellows. Among them, the shielding cover is installed around the moving and static contacts, which has the functions of improving the electric field distribution, condensing metal vapor, and improving the arc breaking ability of the arc extinguishing chamber.

[0014] During the normal operation of the vacuum on-load tap-changer, due to the potential difference between the current-carrying contacts and the shielding cover, the electron current is caused by field emission between the energized contacts and the shielding cover, and the absorption and accumulation effect of the shielding cover on the electrons will form an electric potential on its surface. When the vacuum degree inside the vacuum bubble changes, the vacuum dielectric constant changes accordingly, resulting in a change in the capacitance between the contact-shielding cover-ground, that is, the potential of the shielding cover will change with the change in the vacuum degree.

[0015] The electrostrictive effect is a phenomenon in which a material undergoes mechanical deformation under the action of an electric field. Specifically, when a dielectric material is subjected to an electric field, polarization occurs inside it, causing the molecules or atoms inside the material to rearrange, thus causing mechanical deformation of the material. This effect is reversible, that is, after the electric field is removed, the material will return to its original shape.

[0016] Mach-Zehnder interferometry is a method for precisely measuring the phase difference of light. A coherent light source is split into two beams of light. One beam of test light passes through the test area, and the other beam of reference light does not. The two beams are then combined after traveling the same propagation distance. The combined beams will interfere, thereby reflecting the optical path difference between the two beams (i.e., the change in optical path introduced by the test area).

[0017] The present invention aims to provide a method for detecting the vacuum degree of vacuum bubbles in a vacuum on-load tap changer based on Mach-Zehnder interference and electrostrictive effect, which can realize online monitoring of vacuum bubbles, timely discover abnormal conditions such as vacuum degree drop, improve the operation and maintenance efficiency and fault warning capability of the vacuum on-load tap changer, and ensure the safe and stable operation of the equipment.

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0019] Figure 2 The structure diagram of the vacuum bubble detection system of the vacuum on-load tap changer provided by the embodiment of the present invention is based on the vacuum bubble detection method of the vacuum on-load tap changer provided by the embodiment of the present invention. Figure 2 The vacuum bubble detection system of the vacuum on-load tap-changer is used for detection.

[0020] like Figure 2 As shown, the detection system of the vacuum bubble of the vacuum on-load tap changer includes: a crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photoelectric detector and an oscilloscope.

[0021] The crystal sensor is installed on the inner wall of the vacuum on-load tap changer oil chamber, which is filled with insulating oil.

[0022] One end of the voltage regulator is connected to the mains (220V), and the other end is connected to the input end of the isolation transformer; the output end of the isolation transformer is connected to the two ends of the vacuum bubble. The mains applies high voltage to the two ends of the vacuum bubble through the voltage regulator and the isolation transformer.

[0023] The flat ground electrode is connected between one end of the vacuum bubble and the isolation transformer; the vacuum bubble, the crystal sensor and the flat ground electrode are placed in transformer oil (i.e., insulating oil) so that the shielding cover will generate a detection potential after pressurization.

[0024] The crystal sensor is surrounded by an optical fiber that detects changes in the electric field. One end of the optical fiber is connected to the laser, and the other end is connected to a photodetector and an oscilloscope in sequence; the photodetector and oscilloscope are used to obtain the phase difference.

[0025] In one possible implementation, Figure 3 As shown, the detection system of the vacuum bubble of the vacuum on-load tap changer also includes: two 3dB couplers and an electromagnetic shielding structure.

[0026] Among them, one 3dB coupler is connected between the crystal sensor and the laser; another 3dB coupler is connected between the crystal sensor and the photoelectric detector; and the electromagnetic shielding structure is connected between the two 3dB couplers.

[0027] In this embodiment, two 3dB couplers are used for connecting and transmitting signals respectively. In order to ensure the stability of signal transmission and reduce the influence of external electromagnetic interference, an electromagnetic shielding structure is arranged between the two 3dB couplers to play a shielding and protective role.

[0028] In a possible implementation, the crystal sensor is a lithium niobate LiNbO3 crystal sensor; and the laser is a He-Ne laser.

[0029] In this embodiment, the LiNbO3 crystal sensor has excellent electro-optical effect and high sensitivity, and can convert the received optical signal into an electrical signal, thereby realizing real-time monitoring of the vacuum bubble state. In addition, the He-Ne laser, as a gas laser, has stable output power and a long service life, and can provide a stable light source to ensure the reliability and accuracy of the detection system.

[0030] based on Figure 2 and Figure 3 The test circuit of the vacuum bubble detection system of the vacuum on-load tap changer shown in the figure summarizes the principle of the vacuum bubble detection method of the vacuum on-load tap changer provided by the embodiment of the present invention as follows: when the vacuum degree of the vacuum bubble of the vacuum on-load tap changer changes, the potential of the shielding cover changes, resulting in a change in the surrounding electric field strength; through the LiNbO3 crystal sensor installed on the inner wall of the oil chamber of the vacuum on-load tap changer, the change of the electric field is converted into a change of the optical fiber length based on the electrostrictive effect, and then the Mach-Zehnder interferometer method is used to obtain the phase difference, so as to detect the change of the vacuum degree of the vacuum bubble.

[0031] Specifically, 220V mains electricity applies high voltage to both ends of the vacuum bubble through a voltage regulator and an isolation transformer. To simulate the actual state of the vacuum bubble in operation, a flat ground electrode is set to simulate the transformer oil tank. The vacuum bubble, sensor and ground electrode are all placed in the transformer oil. After pressurization, a potential will be generated on the shielding cover, and a horizontal electric field will be formed between it and the ground electrode, so that the lithium niobate crystal sensor surrounding the optical fiber can be used to detect changes in the electric field.

[0032] In this embodiment, a detection system for a vacuum bubble of a vacuum load-changing switch is constructed by a crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photodetector and an oscilloscope. The real-time monitoring of the vacuum bubble state is realized based on the crystal sensor built into the vacuum bubble. The crystal sensor is arranged on the inner wall of the oil chamber of the vacuum load-changing switch. The optical fiber for detecting the change of the electric field is surrounded by the crystal sensor, and enters and exits from the elbow at the top of the oil chamber, which reduces the structural complexity of the detection system of the vacuum bubble of the vacuum load-changing switch and improves the detection efficiency. The voltage regulator, the isolation transformer and the optical fiber cooperate to convert the electric field change of the vacuum bubble shielding cover into the detection of the optical signal, which not only realizes the amplification of the signal, improves the detection sensitivity, but also increases the anti-interference ability of the measurement signal. The embodiment of the present application can accurately determine the vacuum degree and monitor the change of the vacuum degree during the use of the vacuum bubble, and take countermeasures in time before the vacuum leak occurs to ensure the stability of the operation of the power grid system.

[0033] Figure 4 The implementation flow chart of the method for detecting vacuum bubbles of a vacuum on-load tap changer provided by the embodiment of the present invention is described in detail as follows: Step S401, obtaining the structural parameters, vacuum degree and shielding cover potential of the vacuum bulb of the vacuum on-load tap changer, wherein the structural parameters include: contact radius, shielding cover inner diameter, distance between the shielding cover and the transformer oil tank and conductive rod length.

[0034] In the specific implementation process, the vacuum bulb of the vacuum on-load tap changer has different basic parameters depending on the manufacturer or model. Therefore, before detecting the vacuum degree of the vacuum bulb, it is necessary to obtain the basic structural parameters of the vacuum bulb and determine the reference model or reference value based on the basic structural parameters to determine the vacuum degree of the vacuum bulb based on the measured value and the reference value.

[0035] Step S402: construct an equivalent model of the vacuum bubble according to the structural parameters, and determine a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential.

[0036] Combined with the above introduction, during the normal operation of the vacuum on-load tap changer, due to the potential difference between the current-carrying contacts and the shielding cover, the electron current is caused by field emission between the energized contacts and the shielding cover, and the absorption and cumulative effect of the shielding cover on the electrons will form an electric potential on its surface. Therefore, in the embodiment of the present application, before the vacuum degree detection, an equivalent model of the vacuum bubble is constructed according to the structural parameters to determine the equivalent capacitance between the shielding cover and the conductive rod, the equivalent capacitance between the shielding cover and the transformer tank, and the mean free path of the electrons, so as to facilitate the determination of the shielding cover potential based on the actual detection data and the equivalent model.

[0037] In addition, the reference correlation between the vacuum degree and the shielding cover potential is determined according to the structural parameters, the vacuum degree and the shielding cover potential, so that the vacuum degree of the vacuum bubble can be inferred according to the reference correlation, and more accurate quantitative detection of the vacuum degree of the vacuum bubble can be achieved, thereby effectively determining the state of the vacuum bubble.

[0038] Step S403, input the detection voltage, and obtain the real-time phase difference collected by the photoelectric detector.

[0039] Step S404: determining the vacuum degree of the vacuum bubble of the vacuum on-load tap changer according to the reference association relationship and the real-time phase difference.

[0040] Among them, based on Figure 2 and Figure 3 The vacuum bubble detection system of the vacuum on-load tap changer shown in the figure inputs the detection voltage through the voltage regulator and the isolation transformer, and collects the real-time phase difference through the photoelectric detector, which can be displayed through the oscilloscope, so that the staff can quickly and intuitively predict the state of the vacuum bubble according to the phase display result in a timely and intuitive manner.

[0041] In this embodiment, a vacuum bubble detection system for a vacuum on-load tap changer is constructed based on a crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photodetector, and an oscilloscope. The voltage regulator, the isolation transformer, and the optical fiber cooperate to control the detection voltage input by the voltage regulator, obtain the phase difference collected by the photodetector, improve the detection sensitivity, and increase the anti-interference ability of the measurement signal. Furthermore, the vacuum degree of the vacuum bubble is reversely calculated based on the reference correlation between the vacuum degree and the potential of the shielding cover, the real-time phase difference collected by the photodetector, and the equivalent model of the vacuum bubble constructed in advance, so as to monitor the change of the vacuum degree with precision, take timely countermeasures before vacuum leakage occurs, and ensure the stability of the operation of the power grid system.

[0042] In a possible implementation, determining the vacuum degree of the vacuum bubble of the vacuum on-load tap changer according to the reference association relationship and the real-time phase difference includes: Infer the change in the length of the optical fiber based on the real-time phase difference; The real-time shield potential corresponding to the real-time phase difference is inferred based on the length change; The vacuum degree of the vacuum bubble of the vacuum on-load tap changer is determined according to the real-time shielding cover potential and the reference correlation relationship.

[0043] In this embodiment, the precise measurement of the change in optical fiber length and the real-time monitoring of the shielding cover potential, through the combination of these data with the reference correlation relationship, can effectively evaluate and monitor the vacuum state in the vacuum bubble to ensure the normal operation and safety of the equipment.

[0044] In the specific implementation process, in order to facilitate the accurate measurement of the change in optical fiber length and the real-time monitoring of the shielding cover potential, it is necessary to construct an equivalent model of the vacuum bubble according to the structural parameters in advance, so as to quickly determine the vacuum degree of the vacuum bubble based on the detection data.

[0045] In a possible implementation, an equivalent model of a vacuum bubble is constructed according to structural parameters, including: The equivalent capacitance between the shield and the conductive rod is:

[0046] The equivalent capacitance between the shield and the transformer tank is:

[0047] The mean free path of electrons is:

[0048] In the formula, is the Boltzmann constant; is the internal temperature; is the effective diameter of the gas molecule; is the internal pressure of the vacuum bubble; is the length of the conductive rod; is the contact radius; is the inner diameter of the shield; is the distance between the shielding cover and the transformer tank.

[0049] In one possible implementation, the Boltzmann constant About 1.38×10 -23 J / K; internal temperature is 293K; the effective diameter of the gas molecule About 3.6×10 -10 m.

[0050] In actual implementation, under the normal working pressure of the vacuum bubble, the mean free path is much larger than the geometric size of the vacuum bubble, and collision ionization hardly occurs.

[0051] In a possible implementation, an equivalent model of a vacuum bubble is constructed according to structural parameters, including: The reference correlation relationship between the vacuum degree and the shielding cover potential is determined according to the structural parameters, the vacuum degree and the shielding cover potential, including: The electric field strength between the contact and the shield is:

[0052] The current density caused by field emission is:

[0053] When the gas pressure inside the vacuum bubble rises, the relationship between the induced current density and the field emission current density is:

[0054] The relationship between the potential on the shield and the vacuum degree of the vacuum bubble of the vacuum on-load tap-changer is:

[0055] In the formula, is the charge density; is the work function of the conductive rod and the contact surface; A and B are constants; a and b are constants; is the contact radius; is the inner diameter of the shield; It is the equivalent capacitance between the shielding cover and the transformer oil tank.

[0056] In a possible implementation, the conductive rod and the contact are generally made of copper, and the voltage is taken as 4.3 eV. A and B are constants, and A=1.54×10 -6 A∙eV / V 2 , B=6.83×10 9 V / (m∙eV -3 / 2 ).

[0057] The specific relationship between the above current density and field emission current density and the relationship between the potential on the shielding cover and the vacuum degree of the vacuum bubble of the vacuum on-load tap-changer are derived as follows: When the gas pressure inside the vacuum bubble rises, the mean free path decreases and Thomson discharge may occur. The relationship between the induced current density and the field emission current density is:

[0058] pressure and ionization coefficient The relationship between them is:

[0059] In the formula, a and b are constants; That is:

[0060] Potential on the shield U t It can be expressed as:

[0061] Thus, the correlation between the shielding cover potential and the vacuum degree is established.

[0062] The lithium niobate crystal sensor wrapped around the optical fiber converts the potential change of the shield into the change of the optical fiber length under the action of the electrostrictive effect. The cylindrical lithium niobate crystal undergoes radial deformation under the action of the electric field, and its radial electrostrictive coefficient κ≈2.0×10-16m 2 / V 2 , radial strain With electric field strength The relationship can be expressed as: .

[0063] In a possible implementation, inferring the length change of the optical fiber according to the real-time phase difference includes: The change in optical fiber length is determined according to the following formula:

[0064] In the formula, is the change in optical fiber length; is the phase difference, ; is the wavelength of the laser light source.

[0065] In a possible implementation, the relationship between the length change and the real-time shield potential is as follows:

[0066]

[0067] In the formula, is the number of turns of the optical fiber; is the initial radius of the crystal sensor; is the radial electrostriction coefficient; is the electric field strength; is the real-time shield potential; is the dielectric constant of vacuum; is the equivalent capacitance between the shield and the conductive rod; is the contact radius; is the length of the conductive rod.

[0068] In the actual implementation process, the Mach-Zehnder interferometer method is used to obtain the phase difference to obtain the change in the length of the detection optical fiber, thereby realizing sensitive perception of the vacuum degree in the vacuum bubble. The derivation process of the length change of the optical fiber in the above embodiment is as follows.

[0069] Take the He-Ne fiber laser as an example. The He-Ne fiber laser is a coherent light source, which is divided into test light and reference light after passing through a 3dB coupler. The test fiber is wound on a lithium niobate crystal. The length of the reference fiber is consistent with that of the test fiber. To avoid the influence of the electric field in space, the reference fiber is equipped with an electromagnetic shield after winding.

[0070] The two combined beams will produce interference, and the interference intensity can be expressed as:

[0071] In the formula, I 1 and I 2 are the intensities of the test light and the reference light, Δ θ is the phase difference between the two beams.

[0072] The light intensity of the strongest point (maximum value) and the weakest point (minimum value) of the interference fringes are measured by a photodetector and recorded as I max and I min :

[0073]

[0074] Contrast of interference fringes It can be expressed as:

[0075] The phase difference between the two beams of light can be inferred from the contrast. When the intensities of the two beams of light are equal, the phase difference can be expressed as:

[0076] After obtaining the phase difference, the optical path difference can be inferred , that is, the change in fiber length:

[0077] Where: λ 0 is the wavelength of the laser light source.

[0078] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0079] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0080] Figure 5 The structure diagram of the vacuum bubble detection device of the vacuum on-load tap changer provided by the embodiment of the present invention is shown. For the convenience of description, only the part related to the embodiment of the present invention is shown, which is described in detail as follows: like Figure 5As shown, the vacuum bubble detection device 5 of the vacuum on-load tap changer comprises: The acquisition module 501 is used to acquire the structural parameters, vacuum degree and shielding cover potential of the vacuum on-load tap changer vacuum bubble; wherein the structural parameters include: contact radius, shielding cover inner diameter, distance between the shielding cover and the transformer oil tank and conductive rod length; A relationship building module 502 is used to build an equivalent model of the vacuum bubble according to the structural parameters, and determine a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential; The detection control module 503 is used to input the detection voltage and obtain the real-time phase difference collected by the photoelectric detector; The vacuum degree determination module 504 is used to determine the vacuum degree of the vacuum bubble of the vacuum on-load tap changer according to the reference association relationship and the real-time phase difference.

[0081] In a possible implementation, the vacuum degree determination module 504 is specifically configured to: Infer the change in the length of the optical fiber based on the real-time phase difference; The real-time shield potential corresponding to the real-time phase difference is inferred based on the length change; The vacuum degree of the vacuum bubble of the vacuum on-load tap changer is determined according to the real-time shielding cover potential and the reference correlation relationship.

[0082] In a possible implementation, when the relationship building module 502 is used to build an equivalent model of the vacuum bubble according to the structural parameters, the equivalent capacitance between the shielding cover and the conductive rod is:

[0083] The equivalent capacitance between the shield and the transformer tank is:

[0084] The mean free path of electrons is:

[0085] In the formula, is the Boltzmann constant; is the internal temperature; is the effective diameter of the gas molecule; is the internal pressure of the vacuum bubble; is the length of the conductive rod; is the contact radius; is the inner diameter of the shield; is the distance between the shielding cover and the transformer tank.

[0086] In a possible implementation, the relationship building module 502 is used to determine a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential when building an equivalent model of the vacuum bubble according to the structural parameters, including: The electric field strength between the contact and the shield is:

[0087] The current density caused by field emission is:

[0088] When the gas pressure inside the vacuum bubble rises, the relationship between the induced current density and the field emission current density is:

[0089] The relationship between the potential on the shield and the vacuum degree of the vacuum bubble of the vacuum on-load tap-changer is:

[0090] In the formula, is the charge density; is the work function of the conductive rod and the contact surface; A and B are constants; a and b are constants; is the contact radius; is the inner diameter of the shield; It is the equivalent capacitance between the shielding cover and the transformer oil tank.

[0091] In a possible implementation, the vacuum degree determination module 504 is specifically configured to: The change in optical fiber length is determined according to the following formula:

[0092] In the formula, is the change in optical fiber length; is the phase difference, ; is the wavelength of the laser light source.

[0093] In a possible implementation, the relationship between the length change and the real-time shield potential is as follows:

[0094]

[0095] In the formula, is the number of turns of the optical fiber; is the initial radius of the crystal sensor; is the radial electrostriction coefficient; is the electric field strength; is the real-time shield potential; is the dielectric constant of vacuum; is the equivalent capacitance between the shield and the conductive rod; is the contact radius; is the length of the conductive rod.

[0096] In this embodiment, a vacuum bubble detection system for a vacuum on-load tap changer is constructed based on a crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photodetector, and an oscilloscope. The voltage regulator, the isolation transformer, and the optical fiber cooperate to control the detection voltage input by the voltage regulator, obtain the phase difference collected by the photodetector, improve the detection sensitivity, and increase the anti-interference ability of the measurement signal. Furthermore, the vacuum degree of the vacuum bubble is reversely calculated based on the reference correlation between the vacuum degree and the potential of the shielding cover, the real-time phase difference collected by the photodetector, and the equivalent model of the vacuum bubble constructed in advance, so as to monitor the change of the vacuum degree with precision, take timely countermeasures before vacuum leakage occurs, and ensure the stability of the operation of the power grid system.

[0097] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0098] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0099] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned vacuum on-load tap changer vacuum bubble detection method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A vacuum bubble detection system for a vacuum on-load tap changer, characterized in that: include: A crystal sensor, a voltage regulator, an isolation transformer, a vacuum bubble, a flat ground electrode, transformer oil, an optical fiber, a laser, a photodetector and an oscilloscope; wherein the crystal sensor is mounted on the inner wall of the vacuum on-load tap changer oil chamber; one end of the voltage regulator is connected to the mains, and the other end is connected to the input end of the isolation transformer; the output end of the isolation transformer is connected to both ends of the vacuum bubble; the mains applies high voltage to both ends of the vacuum bubble through the voltage regulator and the isolation transformer; the flat ground electrode is connected between one end of the vacuum bubble and the isolation transformer; the vacuum bubble, the crystal sensor and the flat ground electrode are placed in transformer oil so that the shielding cover will generate a detection potential after pressurization; the crystal sensor is surrounded by an optical fiber for detecting electric field changes, one end of the optical fiber is connected to the laser, and the other end is connected to the photodetector and the oscilloscope in sequence; the photodetector and the oscilloscope are used to obtain phase difference.

2. The vacuum bubble detection system of the vacuum on-load tap changer according to claim 1, characterized in that: Also includes: Two 3dB couplers and an electromagnetic shielding structure; Among them, one of the 3dB couplers is connected between the crystal sensor and the laser; another of the 3dB couplers is connected between the crystal sensor and the photoelectric detector; and the electromagnetic shielding structure is connected between the two 3dB couplers.

3. The vacuum bubble detection system of vacuum on-load tap changer according to claim 1, characterized in that: The crystal sensor is a LiNbO3 crystal sensor; the laser is a He-Ne laser.

4. A method for detecting a vacuum bubble of a vacuum on-load tap changer based on the vacuum bubble detection system of a vacuum on-load tap changer according to any one of claims 1 to 3, characterized in that: include: Obtaining structural parameters, vacuum degree and shielding cover potential of the vacuum on-load tap changer vacuum bubble; wherein the structural parameters include: contact radius, shielding cover inner diameter, distance between the shielding cover and the transformer oil tank and conductive rod length; Constructing an equivalent model of the vacuum bubble according to the structural parameters, and determining a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential; Input the detection voltage and obtain the real-time phase difference collected by the photodetector; The vacuum degree of the vacuum bubble of the vacuum on-load tap changer is determined according to the reference association relationship and the real-time phase difference.

5. The method for detecting vacuum bubbles of a vacuum on-load tap changer according to claim 4, characterized in that: The step of determining the vacuum degree of the vacuum bubble of the vacuum on-load tap changer according to the reference association relationship and the real-time phase difference comprises: Inversely infer the length change of the optical fiber according to the real-time phase difference; Inversely derive the real-time shield potential corresponding to the real-time phase difference according to the length change; The vacuum degree of the vacuum bubble of the vacuum on-load tap changer is determined according to the real-time shielding cover potential and the reference association relationship.

6. The method for detecting vacuum bubbles of a vacuum on-load tap changer according to claim 4 or 5, characterized in that: The equivalent model of the vacuum bubble is constructed according to the structural parameters, comprising: The equivalent capacitance between the shield and the conductive rod is: The equivalent capacitance between the shielding cover and the transformer oil tank is: The mean free path of electrons is: In the formula, is the Boltzmann constant; is the internal temperature; is the effective diameter of the gas molecule; is the internal pressure of the vacuum bubble; is the length of the conductive rod; is the contact radius; is the inner diameter of the shield; is the distance between the shielding cover and the transformer tank.

7. The method for detecting vacuum bubbles of a vacuum on-load tap changer according to claim 6, characterized in that: The equivalent model of the vacuum bubble is constructed according to the structural parameters, comprising: The step of determining a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential comprises: The electric field strength between the contact and the shield is: The current density caused by field emission is: When the gas pressure inside the vacuum bubble rises, the relationship between the induced current density and the field emission current density is: The relationship between the potential on the shield and the vacuum degree of the vacuum bubble of the vacuum on-load tap-changer is: In the formula, is the charge density; is the work function of the conductive rod and the contact surface; A and B are constants; a and b are constants; is the contact radius; is the inner diameter of the shield; is the equivalent capacitance between the shielding cover and the transformer oil tank.

8. The method for detecting vacuum bubbles of a vacuum on-load tap changer according to claim 7, characterized in that: The method of inferring the length change of the optical fiber according to the real-time phase difference comprises: The change in optical fiber length is determined by the following formula: In the formula, is the change in optical fiber length; is the phase difference, ; is the wavelength of the laser light source.

9. The method for detecting vacuum bubbles of a vacuum on-load tap changer according to claim 8, characterized in that: The relationship between the length change and the real-time shield potential is as follows: In the formula, is the number of turns of the optical fiber; is the initial radius of the crystal sensor; is the radial electrostriction coefficient; is the electric field strength; is the real-time shield potential; is the dielectric constant of vacuum; is the equivalent capacitance between the shield and the conductive rod; is the contact radius; is the length of the conductive rod.

10. A vacuum bubble detection device for a vacuum on-load tap changer for executing the vacuum bubble detection method for a vacuum on-load tap changer according to any one of claims 4 to 9, characterized in that: include: An acquisition module is used to acquire the structural parameters, vacuum degree and shielding cover potential of the vacuum bubble of the vacuum on-load tap changer; wherein the structural parameters include: contact radius, shielding cover inner diameter, distance between the shielding cover and the transformer oil tank and conductive rod length; A relationship building module, used to build an equivalent model of the vacuum bubble according to the structural parameters, and determine a reference correlation relationship between the vacuum degree and the shielding cover potential according to the structural parameters, the vacuum degree and the shielding cover potential; A detection control module is used to input a detection voltage and obtain a real-time phase difference collected by a photoelectric detector; The vacuum degree determination module is used to determine the vacuum degree of the vacuum bubble of the vacuum on-load tap changer according to the reference association relationship and the real-time phase difference.

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