Method for detecting and determining insulation electrical aging degree of generator stator winding

Abstract

The invention discloses a method for detecting and determining the insulation electrical aging degree of a generator stator winding. The method comprises the steps that ultrahigh-frequency capacitive coupling sensors are arranged at the A end, the X end and the T end of the generator stator winding respectively to determine the detection wiring mode; setting sensor parameters corresponding to the ultrahigh-frequency capacitive coupling sensor; carrying out detection based on a detection wiring mode and set sensor parameters to obtain partial discharge pulse current signals of the A end, the X end and the T end, and converting the partial discharge pulse current signals into digital signals; and drawing a pulse phase mode pattern based on the digital signal, and calculating the discharge quantity and the discharge amplitude according to the pulse phase mode pattern so as to determine the head end operation voltage electrical aging degree through the calculated head end and tail end discharge amplitude difference. According to the method, the problem that no effective basic partial discharge data is used for reference evaluation can be solved, the problem of large test interference is solved, and objective data of key characteristic quantity electrical aging degree characterization of generator insulation state analysis can be effectively obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of digital intelligent generator insulation state analysis and diagnosis in the electric power industry, and in particular to a method for detecting and determining the electrical aging degree of the insulation of a generator stator winding. Background Art

[0002] The degree of electrothermal aging in the operation of large generators is a key indicator for objectively evaluating the remaining life of hydro-turbine generators. With the continuous grid-connection of solar and wind power generation, the operating conditions of traditional hydropower and thermal power generators have gradually changed accordingly, such as increased load cycle frequency, longer shutdown and maintenance intervals, and higher requirements for generator stability. The overhaul cycle has gradually been extended from 3 to 6 years to 6 to 10 years. There is an urgent need to further improve the state analysis and diagnosis technology to help deepen and implement the state maintenance. The current difficulty is that the reliability of state analysis is not high. Taking the most critical insulation state assessment as an example, there are few effective online monitoring methods, serious online monitoring noise interference, poor data quality, few data samples, and it is difficult to determine the degree of aging without initial reference data. At present, there are almost no effective means in the industry to objectively evaluate the degree of aging. With the deepening of state maintenance, obtaining information on the degree of electrothermal aging of running generators for insulation state analysis is a key issue that needs to be solved urgently. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, the present invention proposes a method for detecting and determining the degree of electrical aging of the insulation of a generator stator winding, which is used to determine the electrical aging state of the insulation of the stator winding of an in-service generator. The method of the present invention makes full use of the structural characteristics of the generator winding, the distribution characteristics of the electrical aging of the insulation in the winding, and the propagation attenuation of the partial discharge in the winding to design a test method, so as to solve the problem that the detection conditions are different and the result data are different, and the aging degree of the detection results cannot be measured without the initial data reference. Specifically, it includes detection test methods, detection wiring, detection equipment parameter selection, detection data analysis and calculation, and detection result evaluation, which are used to determine the electrical aging state of the insulation of the stator winding of an in-service generator.

[0005] To achieve the above-mentioned object, the present invention provides a method for detecting and determining the electrical aging degree of the stator winding insulation of a generator, comprising:

[0006] The ultra-high frequency capacitive coupling sensors are respectively arranged at the A, X and T ends of the generator stator winding to determine the detection wiring mode;

[0007] Set the sensor parameters corresponding to the UHF capacitive coupling sensor;

[0008] Perform detection based on the detection wiring mode and the set sensor parameters to obtain the local discharge pulse current signals at the A end, the X end, and the T end, and convert the local discharge pulse current signals into digital signals;

[0009] A pulse phase pattern diagram is drawn based on the digital signal, and the discharge quantity and discharge amplitude are calculated according to the pulse phase pattern diagram, so as to determine the electrical aging degree of the head-end operating voltage by calculating the difference in the discharge amplitude between the head and tail ends.

[0010] The method for detecting and determining the degree of electrical aging of the insulation of the stator winding of a generator according to an embodiment of the present invention may also have the following additional technical features.

[0011] In one embodiment of the present invention, an X-terminal detection sensor is used to detect a partial discharge signal at the X-terminal, an A-terminal detection sensor is used to detect an insulation partial discharge signal at the A-terminal, and a T-terminal detection sensor is used to detect a partial discharge signal at the T-terminal.

[0012] In one embodiment of the present invention, pressure is applied to the X terminal, and the A, X, and T terminals are measured simultaneously.

[0013] In one embodiment of the present invention, setting sensor parameters corresponding to the ultra-high frequency capacitive coupling sensor includes:

[0014] Select the X-end detection sensor coupling capacitor CX1 and resistor RX1, with parameter capacitor 80pF and resistor 1.5kΩ;

[0015] Select the T-end detection sensor coupling capacitor CX2 and resistor RX2, with parameter capacitor 80pF and resistor 1.5kΩ;

[0016] Select the A-end detection sensor coupling capacitor CA and resistor RA, with parameter capacitor 80pF and resistor 1.5kΩ.

[0017] In one embodiment of the present invention, the detection and recording time is 1 second, that is, 50 sine waves.

[0018] In one embodiment of the present invention, obtaining partial discharge pulse current signals at the A terminal, the X terminal, and the T terminal, and converting the partial discharge pulse current signals into digital signals includes:

[0019] The local discharge pulse current signals from the A terminal, X terminal and T terminal are captured in real time using high-speed pulse recording equipment;

[0020] Amplifying and filtering the captured partial discharge pulse current signal to obtain a pre-processed signal;

[0021] The preprocessed signal is input into an analog-to-digital converter for signal conversion to output a digital signal.

[0022] In one embodiment of the present invention, drawing a pulse phase pattern diagram based on the digital signal includes:

[0023] Screen out effective partial discharge signals from the output digital signals;

[0024] Performing phase analysis and amplitude normalization processing based on the effective partial discharge signal to draw a pulse phase pattern diagram;

[0025] The characteristics of the pulse phase pattern diagram are analyzed, and the electrical aging discharge type of the head and tail ends is determined based on the characteristic analysis results.

[0026] In one embodiment of the present invention, calculating the discharge quantity and the discharge amplitude according to the pulse phase pattern diagram includes:

[0027] Count the number of discharges in each sine wave cycle, add up the total number of discharges, and calculate the average number of discharges in each cycle;

[0028] The maximum discharge amplitude within each sine wave cycle is extracted to calculate the average value of the maximum discharge amplitudes of all cycles.

[0029] The method for detecting and determining the electrical aging degree of the stator winding insulation of the generator in the embodiment of the present invention makes full use of the symmetry of the generator winding structure, the asymmetry of the electrical aging distribution of the winding insulation during long-term operation, and the winding impedance insulation partial discharge propagation attenuation characteristics to design a system test. During the test of the method of the present invention, except for the different sizes of partial discharges due to different aging degrees at the head and tail ends of the winding, the remaining structures and external environments are almost the same. At this time, the electrical aging degree information of the winding can be determined by detecting the difference in partial discharge calculation at the head and tail ends, which can solve the problem of no effective basic partial discharge data for reference evaluation, solve the problem of large test interference, and effectively obtain objective data characterizing the electrical aging degree of the key characteristic quantity for generator insulation status analysis. At the same time, the present invention also helps to promote the in-depth advancement of status maintenance in the power industry and promote the digital and intelligent development of the industry.

[0030] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 is a flow chart of a method for detecting and determining the electrical aging degree of insulation of a generator stator winding according to an embodiment of the present invention;

[0033] Figure 2 is a diagram of a detection system according to an embodiment of the present invention;

[0034] Figure 3 is an operating voltage distribution diagram and an aging area distribution diagram according to an embodiment of the present invention;

[0035] Figure 4 is a test voltage distribution and a partial discharge distribution diagram in a winding according to an embodiment of the present invention;

[0036] Figure 5 is a diagram of insulation partial discharge propagation attenuation in a winding under a test voltage according to an embodiment of the present invention;

[0037] Figure 6 is a detection wiring diagram according to an embodiment of the present invention;

[0038] Figure 7 is a schematic diagram of a first type of spectrum at the A-end head end according to an embodiment of the present invention;

[0039] Figure 8 is a schematic diagram of a first spectrum of the neutral point end of the X end according to an embodiment of the present invention;

[0040] Fig. 9 is a schematic diagram of a second type of spectrum at the A-end head end according to an embodiment of the present invention;

[0041] Fig.10 1 is a schematic diagram of a second spectrum of the neutral point end of the X end according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0043] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0044] The following describes a method for detecting and determining the electrical aging degree of insulation of a stator winding of a generator according to an embodiment of the present invention with reference to the accompanying drawings.

[0045] Figure 1 : is a flow chart of a method for detecting and determining the electrical aging degree of the stator winding insulation of a generator according to an embodiment of the present invention. Figure 1 As shown, including:

[0046] S1, UHF capacitive coupling sensors are respectively placed at the A, X and T ends of the generator stator winding to determine the detection wiring mode;

[0047] S2, setting the sensor parameters corresponding to the UHF capacitive coupling sensor;

[0048] S3, performing detection based on the detection wiring mode and the set sensor parameters to obtain the local discharge pulse current signals at the A end, the X end, and the T end, and converting the local discharge pulse current signals into digital signals;

[0049] S4, drawing a pulse phase pattern diagram based on the digital signal, and calculating the discharge quantity and discharge amplitude according to the pulse phase pattern diagram, so as to determine the electrical aging degree of the head-end operating voltage by calculating the difference in discharge amplitude between the head and tail ends.

[0050] Specifically, the method for detecting and determining the electrical aging of the stator insulation of a generator of the present invention makes full use of the symmetry of the generator winding structure, the asymmetry of the electrical aging distribution of the winding insulation during long-term operation, as well as the winding impedance characteristics and the insulation local discharge propagation attenuation characteristics to design a system test, including test wiring, test voltage selection, detection wiring, and detection parameters, so that the winding insulation is subjected to consistent external conditions during detection. At this time, except for the different aging degrees and local discharge sizes at the head and tail ends of the winding, the rest of the structure and external environment are nearly consistent. At this time, the electrical aging degree of the winding can be determined by detecting the local discharge at the head and tail ends and calculating the difference. The detection system diagram is shown in FIG. Figure 2 shown.

[0051] Among them, the detection system consists of ① stator winding A-end detection sensor, ② stator winding X-end detection sensor, ③ stator winding T-end detection sensor, ④ non-partial discharge industrial frequency step-up transformer, ⑤ partial discharge pulse detection and processing device, and ⑥ step-up control device.

[0052] For example, the operating voltage distribution and aging distribution in the winding are as follows: Figure 3 As shown, it makes full use of the generator winding structure characteristics, operating voltage distribution characteristics, and generator insulation aging distribution characteristics, which has the following advantages: Figure 3 The features shown are as follows:

[0053] 1) The winding structure is basically symmetrical from head to tail;

[0054] 2) In the running state, the voltage at terminal X is low and the voltage at terminal A is high, and the voltage from terminal X to terminal A increases in equal steps, from 0 to the rated voltage of the generator UN / √3kV;

[0055] 3) In the long-term operation state, the insulation electrical aging is concentrated in the high-voltage winding area at the A end, as shown in the "×" symbol area in the figure, and the farther away from the head end, the lower the voltage is, while there is almost no electrical aging in the low voltage area less than 3kV near the X end.

[0056] For example, the voltage distribution in the winding and the distribution characteristics of the insulation partial discharge under the test voltage are as follows: Figure 4 As shown. A 50HZ power frequency AC test voltage UT is applied to the generator winding through a power frequency voltage-adding device without partial discharge, and voltage is added from the X end. Under the external construction frequency voltage, the voltage of the winding from X to A is consistent with UT. Under the action of UT, the partial discharge after the electrothermal aging effect in the stator winding insulation is fully activated, which is the symbol "×" in the figure, and the symbol "Δ" in the figure for the dispersed basic partial discharge caused by the insulation manufacturing and installation process. Its characteristics are as follows Figure 4 As shown, the details are as follows:

[0057] 1) In order to fully reflect the degree of electrical aging of the insulation to ground under the operating voltage, the applied voltage is UN / √3 to activate the partial discharge caused by electrical aging of the insulation to ground;

[0058] 2) In order to fully reflect the degree of electrical aging of phase-to-phase insulation under the operating voltage, the applied voltage is UN to activate the partial discharge caused by electrical aging of the insulation to ground and the partial discharge caused by electrical aging of the phase-to-phase insulation;

[0059] 3) Single-end voltage application is adopted, voltage is applied from the X end, and the other end is connected to a voltage divider to detect that the voltage deviation does not exceed 1kV to avoid voltage deviation;

[0060] 4) Under the test voltage, the winding structure is still symmetrical from head to tail, and the voltage distribution is symmetrical;

[0061] 5) The partial discharge after electrothermal aging in the winding insulation under the test voltage is mainly distributed in the high-voltage wire rod area at the head end of the winding as shown in the figure. The farther away from the head end, the weaker it is. There is almost no partial discharge in the second half of the winding, and the characteristics are asymmetric from head to tail.

[0062] 6) The dispersed basic partial discharge in the winding insulation under the test voltage caused by the manufacturing and installation process is shown as the symbol "Δ" in the figure, which is symmetrical from beginning to end.

[0063] For example, the insulation partial discharge propagation characteristics in the system are as follows: Figure 5 As shown, it has the following characteristics:

[0064] 1) The black pulse indicates partial discharge at the A end under the test voltage, which propagates to the A end and the X end respectively. The pulse signal propagating to the X end gradually attenuates during the propagation process due to the long winding impedance (Z), and the very high frequency component cannot propagate to the X end, so it cannot be detected at the X end; the pulse signal propagating to the A end is closer to A and has less attenuation, so the A end can be detected; the partial discharge signal detected at the A end can represent the partial discharge "×" of insulation electrical aging and the partial discharge "Δ" of basic insulation defect;

[0065] 2) Similarly, the gray pulse of partial discharge at the X end under the test voltage indicates that it propagates to the A end and the X end respectively. The pulse signal propagating to the A end gradually attenuates during the propagation process due to the longer winding impedance (Z), and the very high frequency component cannot propagate to the A end and cannot be detected at the A end; the pulse signal propagating to the X end is closer to X and has less attenuation, so the X end can be detected; the partial discharge signal detected at the X end can represent the partial discharge "Δ" of the basic insulation defect.

[0066] For example, the present invention uses a UHF capacitive coupling sensor to detect partial discharge signals in the insulation at both ends of the winding; fully utilizes the high-frequency signal attenuation effect of the winding impedance to realize that the X-end capacitive sensor detects the X-end partial discharge signal, and the A-end sensor detects the A-end insulation partial discharge signal. In addition, in order to separate the partial discharge influence of the pressurizing equipment T-end, a dual capacitive coupling sensor is used at the X-end. The X-end is pressurized, and the A, X, and T ends are measured simultaneously. The detection wiring is as follows: Figure 6 , the process is as follows:

[0067] 1) Based on the wiring, select the X-end detection sensor coupling capacitor CX1 and resistor RX1, with parameter capacitor 80pF and resistor 1.5kΩ;

[0068] 2) Based on the wiring, select the T-end detection sensor coupling capacitor CX2 and resistor RX2, with parameter capacitor 80pF and resistor 1.5kΩ; the node distance between X and T is 2 meters, and the time difference of 6.6nS at a distance of 2 meters is used to distinguish the partial discharge signal source and eliminate the interference of the T end;

[0069] 3) Based on the wiring, select the A-end detection sensor coupling capacitor CA and resistor RA, with parameter capacitor 80pF and resistor 1.5kΩ;

[0070] 4) Based on the above pressurization method, sensor arrangement and parameter selection, the system symmetrical partial discharge VHF detection is realized;

[0071] 5) Carry out detection, the detection and recording time is 1 second, that is, 50 sine waves, and the local discharge pulse current signals of the A-terminal, X-terminal and T-terminal are recorded by a high-speed pulse recording device and converted into digital signals;

[0072] Furthermore, the detection data is analyzed, a pulse phase pattern diagram PRPD is drawn, and the discharge number NQN and the discharge amplitude QM are calculated.

[0073] Further, the degree of insulation electrical aging is determined by analyzing the insulation electrical aging degree. The partial discharge at the head and tail ends of the winding is tested according to the above methods 1-5, and the type of electrical aging discharge at the head and tail ends is determined through the pattern diagram. The difference in the discharge amplitude at the head and tail ends can be calculated to determine the value of the electrical aging degree of the operating voltage at the head end represented by partial discharge.

[0074] It can be understood that the present invention uses the X-end detection sensor to detect the X-end partial discharge signal, uses the A-end detection sensor to detect the A-end insulation partial discharge signal, and uses the T-end detection sensor to detect the T-end partial discharge signal.

[0075] It can be understood that the present invention uses a high-speed pulse recording device to capture the local discharge pulse current signals from the A terminal, the X terminal and the T terminal in real time; amplifies and filters the captured local discharge pulse current signals to obtain pre-processed signals; and inputs the pre-processed signals into an analog-to-digital converter for signal conversion to output digital signals.

[0076] It can be understood that the present invention selects effective local discharge signals from the output digital signals; performs phase analysis and amplitude normalization processing based on the effective local discharge signals to draw a pulse phase pattern diagram; analyzes the characteristics of the pulse phase pattern diagram, and determines the head and tail end electrical aging discharge type based on the characteristic analysis results.

[0077] It can be understood that the present invention counts the number of discharges in each sine wave cycle, accumulates the total number of discharges to calculate the average number of discharges in each cycle; extracts the maximum discharge amplitude in each sine wave cycle to calculate the average value of the maximum discharge amplitudes of all cycles.

[0078] The specific application examples of the present invention are as follows:

[0079] The stator winding structure of a large 18kV generator has 480 stator slots, 3-phase 4-branch wave winding, 80 wire rods in length, 130V induction voltage of a single wire rod, 10.4kV voltage to ground of the head end wire rod, and 18kV phase-to-phase voltage. After 17 years of operation, it was found that some wire rods at the head end had serious corona electrical aging. The electrical aging degree of the stator winding was determined by the test method of the present invention. Take phase A as an example.

[0080] The first step is to complete the wiring according to the test method of the present invention. The soft connections at the head and tail ends of the generator are removed, the generator and the system are isolated, and the neutral point X end is pressurized through the non-partial discharge power frequency AC withstand voltage test equipment. The head end A is suspended, and the other B and C phases are grounded. A voltage divider is installed at the A end to monitor the head end test voltage to ensure that the head and tail deviation of the test voltage is less than 1kV, that is, there is no large capacity rise effect. The test voltage value is 18 / 1.732, which is 10.4kV and the rated voltage is 18kV.

[0081] The second step is to set the installation parameters of the partial discharge detection system. Two groups of 80pF coupling capacitor sensors are installed at the neutral point with an interval of 2 meters. One group of 80pF coupling capacitor sensors is installed at the A end of the head end. The neutral point adopts the BUS mode of the iris partial discharge offline detection system, the time is set to 6nS, and the system detection frequency band is 40MHZ-350MHZ VHF; the head end also adopts the high-frequency single sensor mode of the iris partial discharge offline detection system to detect the frequency band of 40MHZ-350MHZ.

[0082] In the third step, the test voltage is raised to 10.4 kV, and the data of A and X sensors are collected in sequence, each for 1 second;

[0083] Obtain data and graphs such as Figure 7 , Figure 8 shown.

[0084] Step 4: The test voltage is raised to 18 kV, and the data of A and X sensors are collected in sequence, each for 1 second;

[0085] Obtain data and graphs such as Fig. 9 , Fig.10 shown.

[0086] The fifth step is to calculate the electrical aging data of the insulation to ground, as shown in Table 1:

[0087] Table 1

[0088]

[0089]

[0090] Step 6: Calculate the electrical aging data of phase-to-phase and ground insulation, as shown in Table 2:

[0091] Table 2

[0092]

[0093] In summary, it can be known that the generator insulation assessment methods recommended by the industry regulations are dielectric loss, capacitance, and partial discharge. The problem is that dielectric loss and capacitance are holistic tests that reflect the overall insulation state, while in practice, the weakest point of the insulation is of concern; the partial discharge measurement recommended by the regulations is the overall winding partial discharge PC value, which includes basic partial discharge, dirty partial discharge on the winding surface, and partial discharge in a humid environment, and there is no effective basic reference data, and the degree of insulation aging cannot be objectively determined. The basic partial discharge data detected during the construction period are not very referenceable due to different acquisition conditions and a large time span. The generator stator insulation electrical aging detection and determination method of the present invention makes full use of the symmetry of the generator winding structure, the asymmetry of the long-term electrical aging of the winding insulation, and the winding impedance insulation partial discharge propagation attenuation characteristics to design a system test. During the test, except for the different aging degrees and local discharge sizes at the head and tail ends of the winding, the remaining structures and external environments are nearly consistent. At this time, the electrical aging degree information of the winding can be determined by calculating the difference of the local discharge at the head and tail ends, which solves the problem of basic partial discharge data and the problem of determining the electrical aging of the key characteristic quantity for generator insulation state analysis. The present invention helps to promote the in-depth advancement and implementation of industry status maintenance and promote the digital and intelligent development of the industry.

[0094] According to the method for detecting and determining the electrical aging degree of the generator stator winding insulation of the present invention, the symmetry of the generator winding structure, the asymmetry of the electrical aging distribution of the winding insulation during long-term operation, and the partial discharge propagation attenuation characteristics of the winding impedance insulation are fully utilized to design a system test. The electrical aging degree information of the winding can be determined by detecting the difference in partial discharge calculation at the head and tail ends, thereby solving the problem of having no effective basic partial discharge data for reference evaluation and the problem of large test interference, and effectively obtaining objective data characterizing the electrical aging degree of the key characteristic quantity for generator insulation status analysis.

[0095] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0096] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A method for detecting and determining the electrical aging degree of the stator winding insulation of a generator, characterized in that: include: The ultra-high frequency capacitive coupling sensors are respectively arranged at the A, X and T ends of the generator stator winding to determine the detection wiring mode; Set the sensor parameters corresponding to the UHF capacitive coupling sensor; Perform detection based on the detection wiring mode and the set sensor parameters to obtain the local discharge pulse current signals at the A end, the X end, and the T end, and convert the local discharge pulse current signals into digital signals; A pulse phase pattern diagram is drawn based on the digital signal, and the discharge quantity and discharge amplitude are calculated according to the pulse phase pattern diagram, so as to determine the electrical aging degree of the head-end operating voltage by calculating the difference in the discharge amplitude between the head and tail ends.

2. The method according to claim 1, characterized in that The X-end detection sensor is used to detect the X-end partial discharge signal, the A-end detection sensor is used to detect the A-end insulation partial discharge signal, and the T-end detection sensor is used to detect the T-end partial discharge signal.

3. The method according to claim 2, characterized in that Apply pressure to the X end and measure the A, X, and T ends simultaneously.

4. The method according to claim 2, characterized in that: Set the sensor parameters corresponding to the UHF capacitive coupling sensor, including: Select the X-end detection sensor coupling capacitor CX1 and resistor RX1, with parameter capacitor 80pF and resistor 1.5kΩ; Select the T-end detection sensor coupling capacitor CX2 and resistor RX2, with parameter capacitor 80pF and resistor 1.5kΩ; Select the A-end detection sensor coupling capacitor CA and resistor RA, with parameter capacitor 80pF and resistor 1.5kΩ.

5. The method according to claim 3, characterized in that: The detection and recording time is 1 second, which is 50 sine waves.

6. The method according to claim 5, characterized in that Obtain the partial discharge pulse current signals at the A-terminal, X-terminal and T-terminal, and convert the partial discharge pulse current signals into digital signals, including: The local discharge pulse current signals from the A terminal, X terminal and T terminal are captured in real time using high-speed pulse recording equipment; Amplifying and filtering the captured partial discharge pulse current signal to obtain a pre-processed signal; The preprocessed signal is input into an analog-to-digital converter for signal conversion to output a digital signal.

7. The method according to claim 6, characterized in that Drawing a pulse phase pattern diagram based on the digital signal includes: Screen out effective partial discharge signals from the output digital signals; Performing phase analysis and amplitude normalization processing based on the effective partial discharge signal to draw a pulse phase pattern diagram; The characteristics of the pulse phase pattern diagram are analyzed, and the electrical aging discharge type of the head and tail ends is determined based on the characteristic analysis results.

8. The method according to claim 7, characterized in that Calculate the number and amplitude of discharges based on the pulse phase pattern diagram, including: Count the number of discharges in each sine wave cycle, add up the total number of discharges, and calculate the average number of discharges in each cycle; The maximum discharge amplitude within each sine wave cycle is extracted to calculate the average value of the maximum discharge amplitudes of all cycles.

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