Transformer bushing leakage ultra-high frequency signal detection and diagnosis device and method

Abstract

The present invention discloses a device and method for detecting and diagnosing ultra-high frequency (UHF) signals of transformer bushing leakage, belonging to the technical field of online monitoring of electrical equipment. The specific method includes: collecting the time when the UHF signal arrives at each UHF sensor in the UHF sensor array and the effective value of the UHF signal within a time period t1 starting from the arrival time; judging whether it is a UHF signal leaking from a single bushing based on the number of UHF signals with a time width of t1 collected by each UHF sensor within a time period t2, solving the confidence level of the UHF signal in combination with the attenuation trend of the UHF signal, comparing it with a set threshold, diagnosing whether the UHF signal is a partial discharge inside the bushing, obtaining a diagnosis result, and realizing detection and diagnosis of UHF signals of transformer bushing leakage. The present invention simultaneously detects the electromagnetic waves of the partial discharge of the three-phase bushing, and diagnoses the partial discharge in combination with the propagation law of the electromagnetic waves of the bushing leakage, thereby improving the safe operation level of the transformer.

Description

Technical Field

[0001] The present invention belongs to the technical field of online monitoring of electrical equipment, and in particular relates to a device and method for detecting and diagnosing ultra-high frequency signals leaking from transformer bushings. Background Art

[0002] Partial discharge is the primary cause of sudden failures such as arcing caused by insulation degradation in power transformers. Ultra-high frequency (UHF) antennas detect PD by detecting ultra-high frequency (300MHz-3GHz) electromagnetic waves generated by PD. These antennas offer advantages such as high sensitivity and strong anti-interference capabilities. However, the metal structure of the transformer housing significantly blocks UHF electromagnetic waves. Therefore, a commonly used approach is to install a UHF antenna within the transformer's oil drain valve. However, this approach requires internal modifications to the transformer itself, resulting in complex construction and potential risks, hindering its application in engineering projects. Recent research indicates that UHF electromagnetic waves within the transformer can propagate outward through the transformer bushing, primarily through the capacitor core port at the top of the bushing into free space. Their propagation direction tends to be parallel to the porcelain bushing, and the signal attenuates rapidly with increasing distance from the bushing. Furthermore, transformer bushings are one of the most fault-prone components in transformers. Because bushings are oil-poor, their insulation condition is difficult to detect using oil chromatography. Currently, there is a lack of effective bushing insulation defect detection solutions.

[0003] Prior art document 1 (CN110927538A) discloses a transformer bushing partial discharge monitoring system and method. However, its disadvantage is that it cannot distinguish whether the discharge is generated inside the transformer or inside the bushing, and is easily interfered by external line discharge, which limits the diagnostic accuracy. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention provides a device and method for detecting and diagnosing ultra-high frequency (UHF) signals from transformer bushing leakage. The device comprises a sensor array consisting of an ultra-high frequency (UHF) antenna, a signal conditioning circuit, a processor, a wireless communication module, a directional communication antenna, a power management module, an electromagnetic shielding module, an electromagnetic energy harvesting unit, and a central connecting rod. The sensor array, mounted on a support rod atop the transformer and positioned perpendicular to the terminals of the bushing capacitor core, features at least two measuring points. This allows for simultaneous detection of electromagnetic waves from partial discharge (PD) leaks from three-phase bushings, helping to improve transformer safety.

[0005] The present invention adopts the following technical solutions.

[0006] The first aspect of the present invention provides a transformer bushing leakage ultra-high frequency signal detection and diagnosis device, comprising an ultra-high frequency sensor array, a support column, a bushing module, and a transformer body, specifically comprising:

[0007] The UHF sensor array includes a first array element, a second array element, a third array element, a left connecting rod, a right connecting rod, and a central connecting rod. The first array element and the second array element are connected at both ends of the central connecting rod and are symmetrically located on both sides of the support column. The first array element is connected to the third array element through the left connecting rod, and the second array element is connected to the third array element through the right connecting rod. The third array element is located on the support column below the center line of the first and second array elements.

[0008] The left and right connecting rods are the same length as the central connecting rod. The first, second, and third array elements are used to detect ultra-high frequency signals leaking from the transformer bushing. Together with the left, right, and central connecting rods, they form an equilateral triangle and are parallel to the connection lines of the A-phase bushing, B-phase bushing, and C-phase bushing in the bushing module.

[0009] The bushing module is vertical to the top of the transformer body. The A-phase bushing, B-phase bushing and C-phase bushing are located on the same straight line. The B-phase bushing is located between the A-phase bushing and the C-phase bushing.

[0010] The support column is located vertically above the transformer body and parallel to the B-phase bushing.

[0011] Preferably, the first array element, the second array element, and the third array element respectively include a first UHF sensor, a second UHF sensor, and a third UHF sensor. The first UHF sensor is located between the top of the A-phase bushing and the top of the B-phase bushing of the transformer, the second UHF sensor is located between the top of the B-phase bushing and the top of the C-phase bushing, and the third UHF sensor is located in the middle of the top of the B-phase bushing. The first UHF sensor and the second UHF sensor are used to locate the position of the bushing leaking the UHF signal, and the third UHF sensor is used to determine the axial attenuation trend of the bushing.

[0012] The first UHF sensor, the second UHF sensor and the third UHF sensor each include an UHF antenna and an electromagnetic shielding module;

[0013] The output ends of the UHF antennas are connected to the signal conditioning circuit in the central connecting rod via connecting wires, which are wrapped in an electromagnetic shielding module;

[0014] The electromagnetic shielding module includes a copper mesh and a nickel mesh, is located in the first UHF sensor, the second UHF sensor and the third UHF sensor, and is used to shield other incoming waves except the UHF antenna detection surface.

[0015] Preferably, the central connecting rod includes an electromagnetic shielding module, a signal conditioning circuit, a processor, a wireless communication module and a power management module, specifically including:

[0016] The electromagnetic shielding module is located inside the central connecting rod and outside the signal conditioning circuit, processor, wireless communication module and power management module, and is used to shield the partial discharge ultra-high frequency signal outside the central connecting rod;

[0017] The signal conditioning circuit includes a diode detection circuit for extracting the envelope signal of the UHF antenna; the processor receives the signal output by the signal conditioning circuit for diagnosing partial discharge and outputs the diagnosis result to the wireless communication module;

[0018] The wireless communication module is connected to the directional communication antenna, and is used to transmit the diagnostic results output by the processor to the ground communication terminal through the external directional copper tube communication antenna of the wireless communication module;

[0019] The power management module, which includes a rectifier circuit and a battery, receives AC power input from the electromagnetic energy harvesting unit, rectifies it through the rectifier circuit, and then inputs it into the battery. The battery then powers the signal conditioning circuit, processor, and wireless communication module.

[0020] The electromagnetic energy acquisition unit is located outside the central connecting rod and includes a silicon steel sheet core and an energy acquisition coil. The silicon steel sheet core generates an induced electromotive force, which is then used to generate an induced voltage through the energy acquisition coil. The induced voltage is then input into the power management module.

[0021] A second aspect of the present invention provides a method for detecting and diagnosing ultra-high frequency signals for transformer bushing leakage, which is operated on a device for detecting and diagnosing ultra-high frequency signals for transformer bushing leakage, comprising:

[0022] The time when the UHF signal arrives at each UHF sensor in the UHF sensor array and the effective value of the UHF signal in the time period t1 starting from the arrival time are collected to obtain the UHF signal with a time width of t1 collected by each UHF sensor;

[0023] According to the number of UHF signals with a time width of t1 collected by each UHF sensor in the time period t2, it is determined whether the UHF signal is leaking from a single casing, and a determination result is obtained;

[0024] According to the judgment result, the confidence level of the UHF signal is calculated in combination with the attenuation trend of the UHF signal;

[0025] By comparing the confidence of the obtained UHF signal with a set threshold, it is diagnosed whether the UHF signal is partial discharge inside the bushing, and a diagnosis result is obtained, thereby realizing detection and diagnosis of UHF signal leakage from the transformer bushing.

[0026] Preferably, each UHF sensor in the UHF sensor array first obtains an envelope signal, and is set to determine that the UHF signal arrives at the moment when the envelope signal amplitude is greater than N1 times the background noise, and collects the effective value of the UHF signal within the time period t1 starting from the arrival moment.

[0027] Preferably, if within time t2, each UHF sensor detects only one UHF signal, it is determined that a single bushing is leaking UHF signals;

[0028] If within time t2, each UHF sensor detects multiple UHF signals, and the difference in the amplitude ratio and time delay of the UHF signals detected by each sensor each time is ≤ N2%, it is determined that a single bushing is leaking a UHF signal;

[0029] If the numerical difference between the UHF signal amplitude ratio and the time delay detected by each UHF sensor each time is greater than N2%, it is determined that multiple casings are leaking UHF signals.

[0030] Preferably, if a single casing leaks a UHF signal, the delay state of the UHF signal is set to include symmetric delay, left-biased delay, and right-biased delay according to the coordinates of the UHF sensor and the positioning of the UHF signal delay, and the casing leaking the UHF signal is located according to the delay state of the UHF signal, specifically including:

[0031] If the time delays of the UHF signals detected by the first UHF sensor and the second UHF sensor are the same, it is determined that the time delays are symmetrical, and it is determined that the B-phase bushing is leaking a UHF signal;

[0032] If the signal delay detected by the first UHF sensor is ahead of that detected by the second UHF sensor, it is determined that the delay is biased to the left, and it is determined that the A-phase bushing is leaking UHF signals;

[0033] If the signal delay detected by the first UHF sensor lags behind that detected by the second UHF sensor, it is determined that the delay is biased to the right, and it is determined that the C-phase bushing is leaking a UHF signal.

[0034] Preferably, if a single casing leaks a UHF signal, a theoretical attenuation model of the UHF signal is established based on the distance between the casing leaking the UHF signal and each UHF sensor, and the theoretical amplitude of each UHF signal is obtained. The error between the theoretical amplitude and the actual amplitude of each collected UHF signal is measured using the mean square error, and the error is mapped to a confidence level.

[0035] If multiple casings leak UHF signals, a theoretical attenuation model of the UHF signal is established based on the distances between all casings and each UHF sensor. The theoretical amplitudes of the corresponding UHF signals are obtained. The mean square error is used to measure the error between the actual amplitudes of the collected UHF signals, and the corresponding error is mapped to the confidence level.

[0036] Preferably, the error is mapped to confidence, which is expressed as follows:

[0037] C=exp(-k.Error) (3)

[0038] Where,

[0039] C represents the confidence level,

[0040] k represents the adjustment coefficient,

[0041] Error represents the error, which is expressed by the following formula:

[0042]

[0043] Where,

[0044] N represents the number of UHF sensors,

[0045] A meas (d i ) indicates that the distance between the i-th and the leaking casing is d i The actual amplitude of the UHF sensor,

[0046] A sim (d i ) indicates that the distance between the i-th and the leaking casing is d i The theoretical amplitude of the UHF sensor is expressed as follows:

[0047]

[0048] Where,

[0049] A0 represents the initial amplitude of the signal source,

[0050] α represents the attenuation coefficient.

[0051] Preferably,

[0052] According to the comparison of the confidence level of the obtained UHF signal with a set threshold, diagnosing whether the UHF signal is a partial discharge inside the bushing includes:

[0053] If a UHF signal leaks from a single bushing and the confidence level of the UHF signal is greater than P, the UHF signal comes from inside the located bushing and is determined to be a partial discharge inside the bushing. Otherwise, the UHF signal comes from outside the bushing and is determined to be a discharge from the outer circuit of the bushing.

[0054] If multiple bushings leak UHF signals and the confidence level of the UHF signals is greater than Q, the UHF signals come from inside the located bushings and are judged to be partial discharge inside the bushings. Otherwise, the UHF signals come from outside the bushings and are judged to be discharge from the outer lines of the bushings.

[0055] The beneficial effects of the present invention are as follows:

[0056] The device and method for detecting and diagnosing ultra-high frequency signals of transformer bushing leakage proposed by the present invention do not require modification of the interior of the transformer, and are therefore suitable for deployment on transformers already in operation.

[0057] The sensor array is mounted on a support rod on top of the transformer, perpendicular to the bushing capacitor core port. With at least two measuring points, it can simultaneously detect electromagnetic waves leaking from three-phase bushings. It then uses the propagation patterns of electromagnetic waves leaking from the bushings to diagnose partial discharges (distinguishing between noise and partial discharge signals). The triangular arrangement of the array elements and diagnostic algorithms based on time-domain differences help improve the accuracy of partial discharge detection and accurately determine the source of the discharge signal. Combined with the electromagnetic shielding structure, it reduces interference from external line discharges and avoids misjudgments caused by noise interference.

[0058] The sensor array transmits signals through a wireless communication module, avoiding wired connections at the high-voltage end. This allows the sensor array elements to be installed closer to the high-voltage bushing, helping to improve detection sensitivity, enhance the sensitivity and accuracy of bushing discharge detection, and improve the accuracy of bushing insulation fault warnings.

[0059] The signal processing and communication parts of the sensor array are set in the central connecting rod. Electromagnetic shielding structures are set in the sensor housing and the central connecting rod to prevent interference with the sensor array from ultra-high frequency discharge of the transmission line. Filtering, amplification and detection circuits are also set in the central connecting rod to further improve the signal-to-noise ratio and increase the efficiency of signal transmission. Energy is directly drawn from the transmission line through an external electromagnetic energy acquisition unit, and after rectification, it is input into the battery of the power management module, allowing the sensor array to operate for a long time without maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 Schematic diagram of the UHF signal detection and diagnosis device for casing leakage in the present invention;

[0061] Figure 2 The figure is a flow chart of the method for detecting and diagnosing ultra-high frequency signals leaking from bushings according to the present invention. DETAILED DESCRIPTION

[0062] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts are all within the scope of protection of the present invention.

[0063] This embodiment is directed to partial discharge detection of power transformers and their bushings.

[0064] like Figure 1 As described above, embodiment 1 of the present invention provides a transformer bushing leakage UHF signal detection and diagnosis device, comprising: a UHF sensor array 1, a support column 2, a bushing module 3 and a transformer body 4.

[0065] The UHF sensor array 1 includes a first array element 5, a second array element 6, a third array element 7, a left connecting rod 23, a right connecting rod 24, and a central connecting rod 19. The first array element 5 and the second array element 6 are connected at both ends of the central connecting rod 19 and are symmetrically located on both sides of the support column 2. The first array element 5 is connected to the third array element 7 via the left connecting rod 21, and the second array element 6 is connected to the third array element 7 via the right connecting rod 24. The third array element 7 is located on the support column 2 below the centerline of the first array element 5 and the second array element 6.

[0066] The left connecting rod 23, the right connecting rod 24 and the central connecting rod 19 have the same length. The first array element 5, the second array element 6 and the third array element 7 are used to detect ultra-high frequency signals leaking from the transformer bushing. Together with the left connecting rod 23, the right connecting rod 24 and the central connecting rod 19, they form an equilateral triangle and are parallel to the connection line of the A-phase bushing 8, the B-phase bushing 9 and the C-phase bushing 10 in the bushing module 3.

[0067] The first array element 5, the second array element 6 and the third array element 7 are arranged in an equilateral triangle structure, which can better analyze the propagation characteristics of the UHF signal. This arrangement helps to determine the incoming direction of the UHF signal.

[0068] The UHF antenna in the first array element 5 is located between the top of the A-phase bushing 8 and the B-phase bushing 9 of the transformer, the UHF antenna in the second array element 6 is located between the top of the B-phase bushing 9 and the C-phase bushing 10, and the UHF antenna in the third array element 7 is located in the middle of the top of the B-phase bushing 9. Thus, the UHF sensing array 1 diagnoses partial discharge based on the arrival time and amplitude of the UHF signal.

[0069] The bushing module 3 includes an A-phase bushing 8, a B-phase bushing 9 and a C-phase bushing 10, which are perpendicular to the transformer body 4. The A-phase bushing 8, the B-phase bushing 9 and the C-phase bushing 10 are located on the same straight line. The B-phase bushing 9 is located between the A-phase bushing 8 and the C-phase bushing 10. The support column 2 is located vertically above the transformer body 4. The support column 2 is parallel to the middle phase bushing of the bushing module 3 and parallel to the B-phase bushing 9.

[0070] The first array element 5, the second array element 6, and the third array element 7 respectively include a UHF sensor 2, a second UHF sensor 21, and a third UHF sensor 22. The first UHF sensor 20 is located between the top of the A-phase bushing 8 and the top of the B-phase bushing 9 of the transformer, the second UHF sensor 21 is located between the top of the B-phase bushing 9 and the top of the C-phase bushing 10, and the third UHF sensor 22 is located in the middle of the top of the B-phase bushing 9. It can also be described here that the UHF antenna in the first UHF sensor 20 is located between the top of the A-phase bushing 8 and the top of the B-phase bushing 9 of the transformer, the UHF antenna in the second UHF sensor 21 is located between the top of the B-phase bushing 9 and the top of the C-phase bushing 10, and the UHF antenna in the third UHF sensor 22 is located in the middle of the top of the B-phase bushing 9. The first UHF sensor 20 and the second UHF sensor 21 are used to locate the position of the bushing leaking the UHF signal, and the third UHF sensor 22 is used to determine the axial attenuation trend of the bushing.

[0071] The first UHF sensor 20 , the second UHF sensor 21 and the third UHF sensor 22 each include a UHF antenna 11 and an electromagnetic shielding module 18 .

[0072] The UHF antenna 11 is a flat, two-arm Archimedean spiral antenna. Its conductors are copper, and its substrate is a glass fiber-reinforced epoxy resin laminate. To balance the detection frequency band and miniaturization, the antenna's outer radius is set at 95mm, its inner radius is set at 24mm, the number of turns is set at 10, and the ratio of arm width to arm spacing is set at 0.45. Signal output is achieved through coaxial feeding. The detection frequency band is 500MHz to 2GHz. Fabricated on a printed circuit board, the UHF antenna is placed on the detection surface of the UHF sensor array 1. At least two UHF antennas are required to form the sensor array structure. The output of the UHF antenna is connected to the signal conditioning circuit 12 in the central connecting rod 19 via a connecting wire, which is enclosed within the electromagnetic shielding module 18. In this embodiment, the number of UHF antennas is set to three.

[0073] The central connecting rod 19 includes an electromagnetic shielding module 18, a signal conditioning circuit 12, a processor 13, a wireless communication module 14, and a power management module 17. Specifically, the signal conditioning circuit 12 is connected to the UHF antenna 11. The signal conditioning circuit 12 is a diode detection circuit, comprising a detection diode, capacitor, resistor, etc., used to extract the signal envelope of the UHF antenna 11, reducing the requirements for the sampling system and improving the real-time detection performance. The number of signal conditioning circuits is the same as the number of UHF antennas. The resistor value is set to 10kΩ, the capacitor value is set to 160pF, and the diode is a Schottky diode BAT54. The upper frequency limit of the envelope signal after detection is 20kHz. In this embodiment, the number of signal conditioning circuits is set to three.

[0074] The processor 13 receives the signal output by the signal conditioning circuit 12, diagnoses whether partial discharge occurs based on a preset diagnostic algorithm, and outputs the diagnostic result to the wireless communication module 14. The processor 13 is composed of a development board and has functions such as sampling, signal processing, waveform and key parameter storage. In this embodiment, the processor is composed of a Chuanglong ASD1278 sampling module (8 channels, 24 bits, 144KSPS) and an OMAPL138 development board (CPU main frequency 456MHz, flash memory 512MB), and has functions such as sampling, signal processing, waveform and key parameter storage.

[0075] The wireless communication module 14 is an XY-MBA32B Bluetooth 5.2 communication module, which is connected to the directional communication antenna 15 and transmits the diagnostic results output by the processor 13 to the ground communication terminal via the directional communication antenna 15. The power consumption is about 3.63μA.

[0076] The directional communication antenna 15 is an external directional copper tube communication antenna for the wireless communication module 14, with a transmission distance of up to 295m. It operates in the 2.4GHz ISM frequency band (2.402GHz~2.480GHz) and directionally transmits wireless communication information to the ground communication terminal.

[0077] The electromagnetic energy harvesting unit 16 is located outside the central connecting rod 19 and is an electromagnetic coupling coil comprising a silicon steel sheet core and an energy harvesting coil. The silicon steel sheet core is annular, with the inner diameter, outer diameter, and height of the silicon steel sheet core ring being 40 mm, 70 mm, and 70 mm, respectively. The energy harvesting coil is a winding wound with copper wire. The number of turns of the primary winding is set to 1, and the number of turns of the secondary winding is set to 50, 100, 200, and 400 turns, which are optional and are selected based on the rated value of the transmission line current. Energy is harvested from the transmission line based on the principle of electromagnetic induction, and an induced electromotive force is generated through the silicon steel sheet core, and an induced voltage is generated through the energy harvesting coil, which is then input into the power management module 17.

[0078] The power management module 17, which includes a rectifier circuit and a battery, receives AC power from the electromagnetic energy harvesting unit 16 and supplies it to the battery after rectification, providing long-term power to the signal conditioning circuit 12, processor 13, and wireless communication module 14. The rectifier circuit is based on the LM2596-ADJ buck chip, and to ensure lightweight design, the battery uses a ternary lithium-ion cell with a capacity of 30 Ah.

[0079] The electromagnetic shielding module 18, which includes a copper mesh (high-frequency electromagnetic wave shielding) and a nickel mesh (low-frequency electromagnetic wave shielding), is located inside the first UHF sensor 20, the second UHF sensor 21, the third UHF sensor 22 and the central connecting rod 19, and is located outside the signal conditioning circuit 12, the processor 13, the wireless communication module 14 and the power management module 17. It is used to shield waves from other directions except the detection surface of the UHF antenna 11, and to shield the local discharge UHF signals outside the central connecting rod 19, thereby reducing the impact of surrounding line discharges on the sensor array.

[0080] The UHF sensor housing and the central connecting rod 19 housing are hemispherical to reduce uneven accumulation of charge. The sensor housing and the central connecting rod housing are both made of epoxy resin material.

[0081] like Figure 2 As shown, embodiment 2 of the present invention provides a method for detecting ultra-high frequency signals for transformer bushing leakage, which operates on the ultra-high frequency signal detection device for transformer bushing leakage described in embodiment 1, including:

[0082] Step 1: Collect the time when the UHF signal arrives at each UHF sensor in the UHF sensor array and the effective value of the UHF signal in the time period t1 starting from the arrival time, so as to obtain the UHF signal collected by each UHF sensor with a time width of t1; wherein, for arrival time extraction, each UHF sensor in the UHF sensor array first obtains an envelope signal, adopts a threshold method, sets the time when the envelope signal amplitude is greater than N1 times the background noise, and considers the time as the arrival time of the UHF signal, and collects the effective value of the UHF signal in the time period t1 starting from the arrival time.

[0083] In this embodiment, t1 is set to 20 ns and N1 is set to 5.

[0084] Step 2: Determine whether the signal is a UHF partial discharge signal leaked from a single bushing based on the number of UHF signals with a time width of t1 collected by each UHF sensor in step 1 within time period t2, and obtain a determination result.

[0085] If, within a time period t2, each sensor in the array detects only one UHF signal, it is determined to be a partial discharge from a single bushing. If, within a time period t2, each sensor in the array detects multiple UHF signals, and the amplitude ratio and time delay of the UHF signals detected by each sensor are similar (the numerical difference ≤ N2%), it is preliminarily determined to be a partial discharge from a single bushing. If the amplitude ratio and time delay of the UHF signals detected by each sensor each time vary significantly (the numerical difference > N2%), it is determined to be a partial discharge from multiple bushings.

[0086] In this embodiment, t2 is set to 100 ns and N2 is set to 20%.

[0087] Step 3: According to the judgment result of step 2, the confidence level of the UHF signal is calculated in combination with the attenuation trend of the UHF signal.

[0088] If the UHF signal is leaking from a single casing, positioning is performed based on the coordinates of the UHF sensor and the delay of the UHF signal. The delay state of the UHF signal is set to include three conditions: symmetrical delay, left-biased delay, and right-biased delay. The casing leaking the UHF signal is located based on the delay state of the UHF signal.

[0089] In this embodiment,

[0090] If the UHF signal delays detected by the first UHF sensor 20 and the second UHF sensor 21 are the same, the delays are determined to be symmetrical, and it is determined that the B-phase bushing 9 is leaking UHF signals;

[0091] If the signal delay detected by the first UHF sensor 20 is ahead of that detected by the second UHF sensor 21, it is determined that the delay is to the left, and it is determined that the A-phase bushing 8 is leaking UHF signals;

[0092] If the signal delay detected by the first UHF sensor 20 lags behind that detected by the second UHF sensor 21 , it is determined that the delay is biased to the right, and it is determined that the C-phase bushing 10 is leaking UHF signals.

[0093] If a single casing leaks a UHF signal, a theoretical attenuation model of the UHF signal is established based on the distance between the casing leaking the UHF signal and each UHF sensor, and the theoretical amplitude of each UHF signal is obtained, A sim (d i ) indicates that the distance between the i-th and the leaking casing is d i The theoretical amplitude of the UHF sensor is expressed as follows:

[0094]

[0095] Where,

[0096] A0 represents the initial amplitude of the signal source,

[0097] α represents the attenuation coefficient.

[0098] The mean square error is used to measure the error between the actual amplitude of each collected UHF signal, and the error is mapped to the confidence level; Error represents the error and is expressed as follows:

[0099]

[0100] Where,

[0101] N represents the number of UHF sensors,

[0102] A meas (d i ) indicates that the distance between the i-th and the leaking casing is d i The actual amplitude of the UHF sensor.

[0103] Mapping the error to confidence is expressed as follows:

[0104] C=exp(-k·Error) (3)

[0105] Where,

[0106] C represents the confidence level,

[0107] k represents the adjustment coefficient.

[0108] If multiple casings leak UHF signals, a theoretical attenuation model of the UHF signal is established based on the distances between all casings and each UHF sensor. The theoretical amplitudes of the corresponding UHF signals are obtained. The mean square error is used to measure the error between the actual amplitudes of the collected UHF signals, and the corresponding error is mapped to the confidence level.

[0109] Step 4: Compare the confidence level of the UHF signal obtained in step 3 with the set threshold to diagnose whether the UHF signal is partial discharge inside the bushing, obtain a diagnosis result, and realize detection and diagnosis of UHF signal leakage from the transformer bushing.

[0110] According to the comparison of the confidence level of the obtained UHF signal with a set threshold, diagnosing whether the UHF signal is a partial discharge inside the bushing includes:

[0111] If a UHF signal leaks from a single bushing and the confidence level of the UHF signal is greater than P, the UHF signal comes from inside the located bushing and is determined to be a partial discharge inside the bushing. Otherwise, the UHF signal comes from outside the bushing and is determined to be a discharge from the outer circuit of the bushing.

[0112] If multiple bushings are leaking UHF signals and the confidence level of the UHF signals is greater than Q, the UHF signals originate from within the located bushing and are considered to be internal partial discharge. Otherwise, the UHF signals originate from outside the bushing and are considered to be discharge from the bushing's external circuits. In the case of external circuit discharge, the UHF signals are considered to be interference signals.

[0113] The beneficial effects of the present invention are as follows:

[0114] The device and method for detecting and diagnosing ultra-high frequency signals of transformer bushing leakage proposed by the present invention do not require modification of the interior of the transformer, and are therefore suitable for deployment on transformers already in operation.

[0115] The sensor array is mounted on a support rod on top of the transformer, perpendicular to the bushing capacitor core port. With at least two measuring points, it can simultaneously detect electromagnetic waves leaking from three-phase bushings. It then uses the propagation patterns of electromagnetic waves leaking from the bushings to diagnose partial discharges (distinguishing between noise and partial discharge signals). The triangular arrangement of the array elements and diagnostic algorithms based on time-domain differences help improve the accuracy of partial discharge detection and accurately determine the source of the discharge signal. Combined with the electromagnetic shielding structure, it reduces interference from external line discharges and avoids misjudgments caused by noise interference.

[0116] The sensor array transmits signals through a wireless communication module, avoiding wired connections at the high-voltage end. This allows the sensor array elements to be installed closer to the high-voltage bushing, helping to improve detection sensitivity, enhance the sensitivity and accuracy of bushing discharge detection, and improve the accuracy of bushing insulation fault warnings.

[0117] The signal processing and communication parts of the sensor array are set in the central connecting rod. Electromagnetic shielding structures are set in the sensor housing and the central connecting rod to prevent interference with the sensor array from ultra-high frequency discharge of the transmission line. Filtering, amplification and detection circuits are also set in the central connecting rod to further improve the signal-to-noise ratio and increase the efficiency of signal transmission. Energy is directly drawn from the transmission line through an external electromagnetic energy acquisition unit, and after rectification, it is input into the battery of the power management module, allowing the sensor array to operate for a long time without maintenance.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A transformer bushing leakage ultra-high frequency signal detection and diagnosis device, comprising an ultra-high frequency sensor array (1), a support column (2), a bushing module (3) and a transformer body (4), characterized in that: The ultra-high frequency sensor array (1) comprises a first array element (5), a second array element (6), a third array element (7), a left connecting rod (23), a right connecting rod (24) and a central connecting rod (19); the first array element (5) and the second array element (6) are connected to both ends of the central connecting rod (19) and are symmetrically located on both sides of the support column (2); the first array element (5) is connected to the third array element (7) through the left connecting rod (23); the second array element (6) is connected to the third array element (7) through the right connecting rod (24); and the third array element (7) is located on the support column (2) below the center line of the first array element (5) and the second array element (6); The left connecting rod (23), the right connecting rod (24) and the central connecting rod (19) have the same length. The first array element (5), the second array element (6) and the third array element (7) are used to detect ultra-high frequency signals leaking from the transformer bushing. Together with the left connecting rod (23), the right connecting rod (24) and the central connecting rod (19), they form an equilateral triangle and are parallel to the connection lines of the A-phase bushing (8), the B-phase bushing (9) and the C-phase bushing (10) in the bushing module (3). The bushing module (3) is vertically positioned above the transformer body (4); the A-phase bushing (8), the B-phase bushing (9) and the C-phase bushing (10) are positioned on the same straight line; the B-phase bushing (9) is positioned between the A-phase bushing (8) and the C-phase bushing (10); The support column (2) is vertically located above the transformer body (4) and parallel to the B-phase bushing (9).

2. The transformer bushing leakage ultra-high frequency signal detection and diagnosis device according to claim 1, characterized in that: The first array element (5), the second array element (6) and the third array element (7) respectively comprise a first ultra-high frequency sensor (20), a second ultra-high frequency sensor (21) and a third ultra-high frequency sensor (22); the first ultra-high frequency sensor (20) is located between the top of the A-phase bushing (8) and the top of the B-phase bushing (9) of the transformer; the second ultra-high frequency sensor (21) is located between the top of the B-phase bushing (9) and the top of the C-phase bushing (10); and the third ultra-high frequency sensor (22) is located in the middle of the top of the B-phase bushing (9); the first ultra-high frequency sensor (20) and the second ultra-high frequency sensor (21) are used to locate the position of the bushing leaking the ultra-high frequency signal; and the third ultra-high frequency sensor (22) is used to determine the attenuation trend of the bushing in the axial direction; The first ultra-high frequency sensor (20), the second ultra-high frequency sensor (21), and the third ultra-high frequency sensor (22) each include an ultra-high frequency antenna (11) and an electromagnetic shielding module (18); The output ends of the UHF antenna (11) are connected to the signal conditioning circuit (12) in the central connecting rod (19) via connecting wires, and the connecting wires are wrapped in the electromagnetic shielding module (18); The electromagnetic shielding module (18) comprises a copper mesh and a nickel mesh, is located inside the first UHF sensor (20), the second UHF sensor (21) and the third UHF sensor (22), and is used to shield other incoming waves except the detection surface of the UHF antenna (11).

3. The transformer bushing leakage ultra-high frequency signal detection and diagnosis device according to claim 2, characterized in that: The central connecting rod (19) includes an electromagnetic shielding module (18), a signal conditioning circuit (12), a processor (13), a wireless communication module (14) and a power management module (17); The electromagnetic shielding module (18) is located inside the central connecting rod (19) and outside the signal conditioning circuit (12), the processor (13), the wireless communication module (14) and the power management module (17), and is used to shield the partial discharge ultra-high frequency signal outside the central connecting rod (19); The signal conditioning circuit (12) includes a diode detection circuit for extracting an envelope signal of the ultra-high frequency antenna (11); the processor (13) receives the signal output by the signal conditioning circuit (12) for diagnosing partial discharge and outputs the diagnosis result to the wireless communication module (14); The wireless communication module (14) is connected to the directional communication antenna (15) and is used to transmit the diagnostic result output by the processor (13) to the ground communication terminal through the external directional copper tube communication antenna (15) of the wireless communication module (14); The power management module (17) includes a rectifier circuit and a battery, receives AC power input from the electromagnetic energy acquisition unit (16), rectifies the AC power through the rectifier circuit, and then inputs the AC power into the battery, which then supplies power to the signal conditioning circuit (12), the processor (13), and the wireless communication module (14). The electromagnetic energy acquisition unit (16) is located outside the central connecting rod (19) and includes a silicon steel sheet magnetic core and an energy acquisition coil. The silicon steel sheet magnetic core generates an induced electromotive force and then generates an induced voltage through the energy acquisition coil, and the induced voltage is input into the power management module (17).

4. A method for detecting and diagnosing ultra-high frequency signals of transformer bushing leakage, which is operated on a device for detecting and diagnosing ultra-high frequency signals of transformer bushing leakage according to any one of claims 1 to 3, characterized in that: The time when the UHF signal arrives at each UHF sensor in the UHF sensor array and the effective value of the UHF signal in the time period t1 starting from the arrival time are collected to obtain the UHF signal with a time width of t1 collected by each UHF sensor; According to the number of UHF signals with a time width of t1 collected by each UHF sensor in the time period t2, it is determined whether the UHF signal is leaking from a single casing, and a determination result is obtained; According to the judgment result, the confidence level of the UHF signal is calculated in combination with the attenuation trend of the UHF signal; By comparing the confidence of the obtained UHF signal with a set threshold, it is diagnosed whether the UHF signal is partial discharge inside the bushing, and a diagnosis result is obtained, thereby realizing detection and diagnosis of UHF signal leakage from the transformer bushing.

5. The method for detecting and diagnosing ultra-high frequency signals leaking from transformer bushings according to claim 4, characterized in that: Each UHF sensor in the UHF sensor array first obtains the envelope signal. When the envelope signal amplitude is greater than N1 times the background noise, it is determined that the UHF signal has arrived at that moment. The effective value of the UHF signal in the time period t1 starting from the arrival moment is collected.

6. The method for detecting and diagnosing ultra-high frequency signals leaking from transformer bushings according to claim 5, characterized in that: If within time t2, each UHF sensor detects only one UHF signal, it is determined that a single bushing is leaking UHF signals; If within time t2, each UHF sensor detects multiple UHF signals, and the difference in the amplitude ratio and time delay of the UHF signals detected by each sensor each time is ≤ N2%, it is determined that a single bushing is leaking a UHF signal; If the numerical difference between the UHF signal amplitude ratio and the time delay detected by each UHF sensor each time is greater than N2%, it is determined that multiple casings are leaking UHF signals.

7. The method for detecting and diagnosing ultra-high frequency signals leaking from transformer bushings according to claim 6, characterized in that: If a single casing is leaking a UHF signal, the UHF sensor coordinates and the delay of the UHF signal are used to locate the casing. The delay state of the UHF signal is set to include symmetrical delay, left-biased delay, and right-biased delay. The casing leaking the UHF signal is located based on the delay state of the UHF signal. Specifically, the following steps are performed: If the time delays of the ultra-high frequency signals detected by the first ultra-high frequency sensor (20) and the second ultra-high frequency sensor (21) are the same, it is determined that the time delays are symmetrical, and it is determined that the B-phase bushing (9) is leaking an ultra-high frequency signal; If the signal delay detected by the first UHF sensor (20) is ahead of that detected by the second UHF sensor (21), it is determined that the delay is to the left, and it is determined that the A-phase bushing (8) is leaking UHF signals; If the signal time delay detected by the first UHF sensor (20) lags behind that of the second UHF sensor (21), it is determined that the time delay is right-biased, and it is determined that the C-phase bushing (10) is leaking UHF signals.

8. The method for detecting and diagnosing ultra-high frequency signals leaking from transformer bushings according to claim 7, characterized in that: If a UHF signal is leaking from a single casing, a theoretical attenuation model of the UHF signal is established based on the distance between the casing leaking the UHF signal and each UHF sensor. The theoretical amplitude of each UHF signal is obtained, and the error between the theoretical amplitude and the actual amplitude of each collected UHF signal is measured using the mean square error (MSE). The error is then mapped to a confidence level. If multiple casings leak UHF signals, a theoretical attenuation model of the UHF signal is established based on the distances between all casings and each UHF sensor. The theoretical amplitudes of the corresponding UHF signals are obtained. The mean square error is used to measure the error between the actual amplitudes of the collected UHF signals, and the corresponding error is mapped to the confidence level.

9. The method for detecting and diagnosing ultra-high frequency signals leaking from transformer bushings according to claim 8, characterized in that: Mapping the error to confidence is expressed as follows: C=exp(-k·Error) (3) Where, C represents the confidence level, k represents the adjustment coefficient, Error represents the error, which is expressed by the following formula: Where, N represents the number of UHF sensors, A meas (d i ) indicates that the distance between the i-th and the leaking casing is d i The actual amplitude of the UHF sensor, A sim (d i ) indicates that the distance between the i-th and the leaking casing is d i The theoretical amplitude of the UHF sensor is expressed as follows: Where, A0 represents the initial amplitude of the signal source, α represents the attenuation coefficient.

10. A method for detecting and diagnosing ultra-high frequency signals leaking from transformer bushings according to claim 6 or 9, characterized in that: According to the comparison of the confidence level of the obtained UHF signal with a set threshold, diagnosing whether the UHF signal is a partial discharge inside the bushing includes: If a UHF signal leaks from a single bushing and the confidence level of the UHF signal is greater than P, the UHF signal comes from inside the located bushing and is determined to be a partial discharge inside the bushing. Otherwise, the UHF signal comes from outside the bushing and is determined to be a discharge from the outer circuit of the bushing. If multiple bushings leak UHF signals and the confidence level of the UHF signals is greater than Q, the UHF signals come from inside the located bushings and are judged to be partial discharge inside the bushings. Otherwise, the UHF signals come from outside the bushings and are judged to be discharge from the outer lines of the bushings.

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