Transformer bushing leakage ultrahigh frequency signal detection and diagnosis device and method

Abstract

The invention discloses a transformer bushing leakage ultrahigh frequency signal detection and diagnosis device and method, and belongs to the technical field of electrical equipment online monitoring. The method specifically comprises the following steps: acquiring the moment when an ultrahigh-frequency signal reaches each ultrahigh-frequency sensor in an ultrahigh-frequency sensor array and the effective value of the ultrahigh-frequency signal within a time period t1 from the arrival moment; according to the number of ultrahigh-frequency signals with the time width of t1 acquired by each ultrahigh-frequency sensor in the time period t2, judging whether the ultrahigh-frequency signals are leaked from a single bushing, solving the confidence coefficient of the ultrahigh-frequency signals by combining the attenuation trend of the ultrahigh-frequency signals, comparing with a set threshold value, and diagnosing whether the ultrahigh-frequency signals are partial discharge in the bushing or not. Therefore, the ultrahigh-frequency signal detection and diagnosis for the leakage of the transformer bushing are realized. The leakage partial discharge electromagnetic waves of the three-phase bushing are detected at the same time, partial discharge is diagnosed in combination with the propagation rule of the leakage electromagnetic waves of the bushing, and the safe operation level of the transformer is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of online monitoring of electrical equipment, and in particular relates to a transformer bushing leakage ultra-high frequency signal detection and diagnosis device and method. Background Art

[0002] Partial discharge is the main cause of sudden faults such as arc breakdown caused by insulation degradation of power transformers. UHF antennas detect partial discharge by detecting UHF (300MHz~3GHz) electromagnetic waves excited by partial discharge, and have the advantages of high detection sensitivity and strong anti-interference ability. However, the metal structure of the transformer shell has a significant blocking effect on UHF electromagnetic waves. Therefore, the method of installing UHF antennas inside the transformer oil drain valve is generally adopted. However, this method requires modification of the transformer body, which is complex to construct and may introduce risks, and has great resistance to engineering application. The latest research shows that the UHF electromagnetic waves inside the transformer can propagate outward through the transformer bushing, mainly through the capacitor core port at the top of the bushing to the free space. Its propagation direction tends to be parallel to the porcelain bushing, and the signal decays rapidly as the distance from the porcelain bushing increases. In addition, the transformer bushing is one of the main components in the transformer that is most prone to failure. Since the bushing is an oil-less device, it is difficult to detect its insulation status through oil chromatography. At present, there is still a lack of effective bushing insulation defect detection scheme.

[0003] Prior art document 1 (CN110927538A) discloses a transformer bushing partial discharge monitoring system and method, which has the disadvantage 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] In order to solve the deficiencies in the prior art, the present invention provides a transformer bushing leakage UHF signal detection and diagnosis device and method, wherein the sensor array is composed of a 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 acquisition unit, a central connecting rod, etc. The sensor array is installed on the support rod at the top of the transformer, and is placed at a position perpendicular to the bushing capacitor core port. At least two measuring points are set, and the leakage partial discharge electromagnetic waves of the three-phase bushing can be detected at the same time, which helps to improve the safe operation level of the transformer.

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

[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 comprises 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 supporting 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 supporting column below the center line of the first array element and the second array element.

[0008] The left connecting rod, the right connecting rod and the central connecting rod have the same length. The first array element, the second array element and the third array element are used to detect the ultra-high frequency signal leaked from the transformer bushing. They form an equilateral triangle together with the left connecting rod, the right connecting rod and the central connecting rod, and are parallel to the connection lines of the A-phase bushing, the B-phase bushing and the 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 B-phase bushing of the transformer, the second UHF sensor is located between the top of the B-phase bushing and the C-phase bushing, 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 a 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, and the connecting wires are wrapped in an electromagnetic shielding module;

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

[0015] Preferably, the central connecting rod comprises 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, the processor, the wireless communication module and the 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 accesses 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 result 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 includes a rectifier circuit and a battery, receives the AC power input by the electromagnetic energy acquisition unit, rectifies it through the rectifier circuit, and then inputs it into the battery, and then the battery powers the signal conditioning circuit, the processor, and the 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 induced electromotive force is generated through the silicon steel sheet core and then the induced voltage is generated through the energy acquisition coil, and the induced voltage is input into the power management module.

[0021] A second aspect of the present invention provides a transformer bushing leakage ultra-high frequency signal detection and diagnosis method, which is run on a transformer bushing leakage ultra-high frequency signal detection and diagnosis device, comprising:

[0022] 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 a time period t1 starting from the arrival time, and 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 it is a UHF signal leaking from a single casing, and a determination result is obtained;

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

[0025] By comparing the obtained confidence level of the 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 acquires an envelope signal, and 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, and the effective value of the UHF signal in the time period t1 starting from the arrival moment is collected.

[0027] Preferably, if within time t2, each UHF sensor detects the UHF signal only once, it is determined that a single bushing leaks the UHF signal;

[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 casing leaks UHF signals;

[0029] If the numerical difference between the amplitude ratio and the time delay of the UHF signal 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, according to the coordinates of the UHF sensor and the positioning of the delay of the UHF signal, the delay state of the UHF signal is set to include delay symmetry, delay to the left, and delay to the right, and the casing leaking the UHF signal is positioned 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 a UHF signal;

[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 according to the distance between the casing leaking the UHF signal and each UHF sensor, the theoretical amplitude of each UHF signal is obtained, 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 a confidence level;

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

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

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

[0038] In the formula,

[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] In the formula,

[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] In the formula,

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

[0050] α represents the attenuation coefficient.

[0051] Preferably,

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

[0053] If a single bushing leaks a UHF signal, and the confidence level of the UHF signal is greater than P, the UHF signal comes from the located bushing, and the UHF signal is determined to be a local discharge inside the bushing; otherwise, the UHF signal comes from outside the bushing, and the UHF signal is determined to be a discharge of the outer line of the bushing;

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

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

[0056] The transformer bushing leakage ultra-high frequency signal detection and diagnosis device and method proposed by the present invention do not require modification of the transformer interior, and are conducive to deployment on transformers that have been put into operation;

[0057] The sensor array is installed on the support rod on the top of the transformer, and is placed at a position perpendicular to the port of the bushing capacitor core. At least two measuring points are set to detect the leakage of partial discharge electromagnetic waves from the three-phase bushing at the same time, and diagnose partial discharge (distinguish between noise and partial discharge signals) in combination with the propagation law of the electromagnetic waves leaked from the bushing. The triangular array elements and the diagnostic algorithm based on time domain difference etc. help to improve the accuracy of partial discharge detection, accurately determine the source of the discharge signal, and combine with the electromagnetic shielding structure to reduce the interference of external line discharge and avoid misjudgment caused by noise interference.

[0058] The sensor array transmits signals through the wireless communication module to avoid wired connection at the high-voltage end, so that the sensor array elements can be installed closer to the high-voltage bushing, which helps to improve the detection sensitivity, improve the sensitivity and accuracy of bushing discharge detection, and improve the accuracy of bushing insulation fault warning;

[0059] The signal processing and communication parts of the sensor array are arranged in the central connecting rod. Electromagnetic shielding structures are arranged in the sensor housing and the central connecting rod to avoid interference of ultra-high frequency discharge of the transmission line on the sensor array. Filtering, amplification and detection circuits are also arranged in the central connecting rod to further improve the signal-to-noise ratio and improve the signal transmission efficiency. Energy is directly taken 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, so that the sensor array can operate for a long time without maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0061] Figure 2 It is a schematic diagram of the flow chart of the method for detecting and diagnosing the casing leakage ultra-high frequency signal in the present invention. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the 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 creative work 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 proposes 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 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 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 through the left connecting rod 21, and the second array element 6 is connected to the third array element 7 through the right connecting rod 24. 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.

[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 the ultra-high frequency signal leaked 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.

[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] Among them, 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, so that the UHF sensor 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 top of 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 vertically located 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 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 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 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 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 bushing position of the leaking UHF signal, and the third UHF sensor 22 is used to determine the attenuation trend of the bushing axial direction;

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

[0072] The UHF antenna 11 is a flat double-arm Archimedean spiral antenna. The antenna conductor is copper. The antenna base is made of glass fiber reinforced epoxy resin laminate. In order to take into account the detection frequency band and miniaturization, the outer radius of the antenna spiral is set to 95mm, the inner radius of the antenna is set to 24mm, the number of spiral turns is set to 10 turns, the ratio of arm width to arm spacing is set to 0.45, and the signal is output by coaxial feeding. The detection frequency band is 500MHz~2GHz. The UHF antenna is made 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 a sensor array structure. The output end of the UHF antenna is connected to the signal conditioning circuit 12 in the central connecting rod 19 through a connecting line, and the connecting line is wrapped in the electromagnetic shielding module 18. In this embodiment, the number of UHF antennas is set to 3.

[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 including: the signal conditioning circuit 12 is connected to the UHF antenna 11, the signal conditioning circuit 12 is a diode detection circuit, including a detection diode, a capacitor, a resistor, etc., which is used to extract the signal envelope of the UHF antenna 11, reduce the requirements for the sampling system and improve the real-time detection, and the number of signal conditioning circuits is the same as the number of UHF antennas. The resistance value is set to 10kΩ, the capacitance value is set to 160pF, the diode is selected as a Schottky diode BAT54, and the upper frequency limit of the envelope signal after detection is 20kHz. In this embodiment, the number of signal conditioning circuits is set to 3.

[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 the functions of 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 the functions of 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 result output by the processor 13 to the ground communication terminal through 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, 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 extraction unit 16 is located outside the central connecting rod 19 and is an electromagnetic coupling coil, which includes a silicon steel sheet core and an energy extraction coil. The silicon steel sheet core is annular, and the inner diameter, outer diameter and height of the silicon steel sheet core ring are 40mm, 70mm, and 70mm respectively. The energy extraction 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. It is selected according to the rated value of the transmission line current. It extracts energy from the transmission line based on the principle of electromagnetic induction, generates an induced electromotive force through the silicon steel sheet core, and then generates an induced voltage through the energy extraction coil, and inputs the induced voltage to the power management module 17.

[0078] The power management module 17 includes a rectifier circuit and a battery, receives the AC power input by the electromagnetic energy acquisition unit 16, and inputs it to the battery after rectification to provide long-term power for the signal conditioning circuit 12, the processor 13 and the wireless communication module 14. The rectifier circuit is constructed based on the BUCK chip LM2596-ADJ. In order to take into account the lightweight, the battery selects a ternary lithium battery with a battery capacity of 30Ah.

[0079] The electromagnetic shielding module 18, including 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 in shape to reduce uneven accumulation of electric 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 proposes a method for detecting ultra-high frequency signals for transformer bushing leakage, which is operated on an ultra-high frequency signal detection device for transformer bushing leakage described in Embodiment 1, and includes:

[0082] Step 1, 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 in the time period t1 starting from the arrival time, to obtain the UHF signal with a time width of t1 collected by each UHF sensor; wherein, for arrival time extraction, each UHF sensor in the UHF sensor array first obtains an envelope signal, and adopts a threshold method to set that when the amplitude of the envelope signal is greater than N1 times the background noise, the moment is considered to be 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 20 ns and N1 is 5.

[0084] Step 2: determine whether it is a UHF partial discharge signal leaked from a single bushing according to 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 period of time t2, each sensor in the array detects only one UHF signal, it is determined to be a partial discharge generated by a single bushing. If within a period of time 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 close each time (the numerical difference is ≤ N2%), it is preliminarily determined to be a partial discharge generated by a single bushing; if the amplitude ratio and time delay of the UHF signals detected by each sensor each time have a large change (the numerical difference is > N2%), it is determined to be a UHF signal leaked from multiple bushings.

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

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

[0088] If the UHF signal is leaked from a single casing, the 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 situations: 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 time delays of the UHF signals detected by the first UHF sensor 20 and the second UHF sensor 21 are the same, it is determined that the time delays are symmetrical, and it is determined that the B-phase bushing 9 leaks 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 biased 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] In the formula,

[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, which is expressed by the following formula:

[0099]

[0100] In the formula,

[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] In the formula,

[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 distance between all casings and each UHF sensor to obtain the corresponding theoretical amplitude of each UHF signal. The mean square error is used to measure the error between the actual amplitude of each collected UHF signal, and the corresponding error is mapped to confidence.

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

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

[0111] If a single bushing leaks a UHF signal, and the confidence level of the UHF signal is greater than P, the UHF signal comes from the located bushing, and the UHF signal is determined to be a local discharge inside the bushing; otherwise, the UHF signal comes from outside the bushing, and the UHF signal is determined to be a discharge of the outer line of the bushing;

[0112] If multiple bushings leak UHF signals, and the confidence of the UHF signals is greater than Q, the UHF signals come from the located bushings, and the UHF signals are judged to be partial discharge inside the bushings. Otherwise, the UHF signals come from outside the bushings, and the UHF signals are judged to be discharges from the outer lines of the bushings. When the outer lines of the bushings are discharged, the UHF signals are judged to be interference signals.

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

[0114] The transformer bushing leakage ultra-high frequency signal detection and diagnosis device and method proposed by the present invention do not require modification of the transformer interior, and are conducive to deployment on transformers that have been put into operation;

[0115] The sensor array is installed on the support rod on the top of the transformer, and is placed at a position perpendicular to the port of the bushing capacitor core. At least two measuring points are set to detect the leakage of partial discharge electromagnetic waves from the three-phase bushing at the same time, and diagnose partial discharge (distinguish between noise and partial discharge signals) in combination with the propagation law of the electromagnetic waves leaked from the bushing. The triangular array elements and the diagnostic algorithm based on time domain difference etc. help to improve the accuracy of partial discharge detection, accurately determine the source of the discharge signal, and combine with the electromagnetic shielding structure to reduce the interference of external line discharge and avoid misjudgment caused by noise interference.

[0116] The sensor array transmits signals through the wireless communication module to avoid wired connection at the high-voltage end, so that the sensor array elements can be installed closer to the high-voltage bushing, which helps to improve the detection sensitivity, improve the sensitivity and accuracy of bushing discharge detection, and improve the accuracy of bushing insulation fault warning;

[0117] The signal processing and communication parts of the sensor array are arranged in the central connecting rod. Electromagnetic shielding structures are arranged in the sensor housing and the central connecting rod to avoid interference of ultra-high frequency discharge of the transmission line on the sensor array. Filtering, amplification and detection circuits are also arranged in the central connecting rod to further improve the signal-to-noise ratio and improve the signal transmission efficiency. Energy is directly taken 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, so that the sensor array can 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 relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within 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 the two ends of the central connecting rod (19) and are symmetrically located on both sides of a support column (2); the first array element (5) is connected to the third array element (7) via a left connecting rod (21); the second array element (6) is connected to the third array element (7) via a 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 disposed above 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 vertically located above the transformer body (4) and parallel to the B-phase bushing (9).

2. A 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 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 C-phase bushing (10); 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 axial attenuation trend of the bushing; The first UHF sensor (20), the second UHF sensor (21) and the third UHF sensor (22) all include a UHF 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 an 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. A transformer bushing leakage ultra-high frequency signal detection and diagnosis device according to claim 2, characterized in that: The central connecting rod (19) comprises 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 UHF antenna (11); the processor (13) receives a 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) to directionally transmit the wireless communication information; The power management module (17) comprises a rectifier circuit and a storage battery, receives the AC power input by the electromagnetic energy acquisition unit (16), rectifies the AC power by the rectifier circuit, and then inputs the AC power to the storage battery, and then supplies power to the signal conditioning circuit (12), the processor (13) and the wireless communication module (14) through the storage battery; 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. The induced voltage is input into the power management module (17).

4. A transformer bushing leakage ultra-high frequency signal detection and diagnosis method, running on a transformer bushing leakage ultra-high frequency signal detection and diagnosis device as described in any one of claims 1 to 3, characterized in that: 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 a time period t1 starting from the arrival time, and 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 it is a UHF signal leaking from a single casing, and a determination result is obtained; According to the judgment result, the confidence of the UHF signal is solved in combination with the attenuation trend of the UHF signal; By comparing the obtained confidence level of the 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. A transformer bushing leakage ultra-high frequency signal detection and diagnosis method according to claim 4, characterized in that: Each UHF sensor in the UHF sensor array first obtains an envelope signal, and when the envelope signal amplitude is greater than N1 times the background noise, it is determined that the UHF signal has arrived at this moment, and the effective value of the UHF signal in the time period t1 starting from the arrival moment is collected.

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

7. A transformer bushing leakage ultra-high frequency signal detection and diagnosis method according to claim 6, characterized in that: If a single bushing leaks a UHF signal, according to the coordinates of the UHF sensor and the positioning of the UHF signal delay, the UHF signal delay state is set to include delay symmetry, delay biased to the left, and delay biased to the right, and the bushing leaking the UHF signal is located according to the delay state of the UHF signal, specifically including: If the time delays of the UHF signals detected by the first UHF sensor (20) and the second UHF 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 the UHF signal; If the signal time delay detected by the first UHF sensor (20) is ahead of that detected by the second UHF sensor (21), it is determined that the time delay is biased to the left, and it is determined that the A-phase bushing (8) is leaking a UHF signal; If the signal time delay detected by the first UHF sensor (20) lags behind that detected by the second UHF sensor (21), it is determined that the time delay is biased to the right, and it is determined that the C-phase bushing (10) is leaking a UHF signal.

8. A transformer bushing leakage ultra-high frequency signal detection and diagnosis method according to claim 7, characterized in that: 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 measured value and the actual amplitude of each collected UHF signal is measured using the mean square error, and the error is mapped to confidence. If multiple casings leak UHF signals, a theoretical attenuation model of the UHF signal is established based on the distance between all casings and each UHF sensor to obtain the corresponding theoretical amplitude of each UHF signal. The mean square error is used to measure the error between the actual amplitude of each collected UHF signal, and the corresponding error is mapped to confidence.

9. A transformer bushing leakage ultra-high frequency signal detection and diagnosis method according to claim 8, characterized in that: Mapping the error to confidence is expressed as follows: C=exp(-k·Error) (3) In the formula, C represents the confidence level, k represents the adjustment coefficient, Error represents the error, which is expressed by the following formula: In the formula, 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: In the formula, A0 represents the initial amplitude of the signal source, α represents the attenuation coefficient.

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

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