A converter transformer partial discharge testing platform and method based on the single-unit balancing method

Abstract

This invention discloses a partial discharge (PD) testing platform and method for converter transformers based on the single-unit balancing method. The platform includes a transformer body, a pressurizing unit, and a detection unit. The transformer body has a grid-side bushing and two valve-side bushings on the outside of the tank. The pressurizing unit and the detection unit are connected in parallel between the two valve-side bushings of the tank. The detection unit's magnetic core is wound with a detection winding and symmetrically arranged first and second balancing windings. One end of each balancing winding is connected to and grounded, and the other ends are electrically connected to the two valve-side windings via coupling capacitors. The detection winding is connected to a PD detector via BNC terminals. This invention achieves separation of the PD pulse current signal by using two symmetrically arranged balanced impedances when the impedance core is near zero magnetic flux. This eliminates the need for two similar samples for testing, simplifies the test wiring, and provides superior anti-interference performance.

Description

Technical Field

[0001] This invention relates to the field of power testing technology, specifically to a converter transformer partial discharge testing platform and method based on the individual unit balancing method. Background Technology

[0002] In power systems, converter transformers, as key equipment for electrical energy conversion and transmission, connect to both AC and DC transmission systems, playing a crucial role. The operating conditions of the valve-side winding insulation of converter transformers are more complex and severe than those of AC power transformers. Once a fault occurs, the effects of pulses and harmonics can lead to serious malfunctions, causing significant personal injury and property damage. Performing partial discharge tests on the valve-side windings of converter transformers can check their insulation performance, identify potential defects, and facilitate the development of relevant solutions.

[0003] The pulsed current method is one of the most effective techniques in field testing. Its detection circuit connection methods are divided into the direct method and the balanced method. The existing balanced method requires two similar test samples, one of which acts as a coupling capacitor, providing strong anti-interference capabilities. However, the wiring of the existing balanced method is complex, and it is difficult to implement using two similar samples in a converter transformer test site. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a converter transformer partial discharge test platform based on the single-unit balancing method, which solves the problem of difficulty in testing with two similar samples at the converter transformer test site, and also solves the problem of interference during testing.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a converter transformer partial discharge test platform based on the single-unit balancing method, comprising a transformer body, a pressurizing unit, and a detection unit. The transformer body includes an oil tank, and a grid-side bushing, a first valve-side bushing, and a second valve-side bushing are provided on the outside of the oil tank. The pressurizing unit and the detection unit are connected in parallel between the first valve-side bushing and the second valve-side bushing of the oil tank. The detection unit includes an input module and a partial discharge detector. The input module includes a shielded box, and a magnetic core is installed inside the shielded box. A first balancing winding, a second balancing winding, and a detection winding are wound on the magnetic core. The first balancing winding and the second balancing winding are arranged symmetrically and crosswise. The end of the first balancing winding is connected to the beginning of the second balancing winding and grounded. The beginning of the first balancing winding is electrically connected to the first valve-side bushing of the oil tank through a coupling capacitor. A detection resistor is connected in parallel to both ends of the detection winding, and the detection resistor is connected to the partial discharge detector through a terminal.

[0006] Preferably, a shielding layer is provided on the outside of the magnetic core and the detection winding.

[0007] Preferably, the oil tank further includes a grid-side winding and a valve-side winding. The grid-side winding and the valve-side winding are provided inside the oil tank. The high-voltage end of the grid-side winding is electrically connected to the grid-side bushing, and the low-voltage end of the grid-side winding is grounded. The two terminals of the valve-side winding are electrically connected to the first valve-side bushing and the second valve-side bushing, respectively. The grid-side winding is provided with multiple taps.

[0008] Preferably, a partial discharge generating unit is installed on the oil tank. The partial discharge generating unit includes a fixing plate and contacts. An insulating fixing plate is vertically installed inside the oil tank. Multiple contacts are evenly arranged on the fixing plate along the vertical direction. The number of multiple taps on the grid-side winding is equal to the number of contacts on the fixing plate. Each of the multiple taps is electrically connected to a contact.

[0009] Preferably, the partial discharge generating unit further includes a connecting bracket, an adjusting plate, and a discharge needle; the adjusting plate is movably mounted on the oil tank, the adjusting plate is vertically mounted on the oil tank, the adjusting plate is mounted on the adjusting plate, the adjusting plate reciprocates in the vertical direction, and the discharge needle corresponds to different contacts; the top of the oil tank has an opening, and a connecting bracket is welded to the top opening of the oil tank, the connecting bracket has several connecting holes, the connecting holes are horizontally mounted on the connecting bracket, the adjusting plate is inserted into the top opening of the oil tank, the adjusting plate has multiple adjusting holes, the number of adjusting holes is equal to the number of contacts of the fixed plate, the distance between adjacent adjusting holes is equal to the distance between adjacent contacts, and the adjusting holes on the adjusting plate and the connecting holes on the connecting bracket are connected by pins.

[0010] Preferably, an observation window is installed on the side of the fuel tank.

[0011] Preferably, a current-limiting reactor and a voltage divider are electrically connected at the mesh-side bushing of the oil tank.

[0012] Preferably, a signal generator is electrically connected to the mesh side sleeve of the oil tank.

[0013] A method for testing the partial discharge of converter transformers based on the individual unit balancing method includes the following steps:

[0014] Step S1: Set up two converter transformer partial discharge test platforms;

[0015] The two converter transformer partial discharge test platforms are divided into a converter transformer partial discharge propagation characteristic test platform and a converter transformer partial discharge anti-interference test platform.

[0016] Step S2: Partial discharge quantity calibration, specifically:

[0017] A known charge Q0 = U0C0 is injected into the transformer body from the grid-side bushing using a calibration pulse generator, and the detection unit responds with L'. The calibration pulse generator is then removed, and a voltage test is performed. When the transformer body discharges internally, the detection unit responds with L, yielding the conversion factor K.h =L / L′, obtained through the conversion factor K h The apparent discharge quantity is obtained by adding the pulse voltage amplitude U0 and the series small capacitor C0; then, the apparent discharge quantity is obtained by using the conversion factor K. h The apparent discharge quantity is correlated with the measured pulse voltage amplitude. The partial discharge calibrator is connected to the transformer body. The output of the partial discharge calibrator is adjusted to different discharge quantities. The relationship between the pulse voltage amplitude and the apparent discharge quantity is plotted.

[0018] In the formula, Q0 represents the charge, U0 represents the pulse voltage amplitude, V, C0 represents the series small capacitor, pF, K h Indicates the conversion factor;

[0019] Step S3: Determine the initial discharge voltage and the test voltage, specifically as follows:

[0020] The voltage input to the transformer body is slowly increased. After five initial discharge voltage tests at each partial discharge location, the average value of the initial discharge voltage is obtained by plotting a Weibull distribution diagram. Under the condition that partial discharge can occur at all locations, subsequent test voltages are selected, and the selected test voltages are all higher than the average value of the initial voltage at that discharge location.

[0021] Step S4: Perform partial discharge detection test on the transformer, specifically as follows:

[0022] The transformer body was subjected to partial discharge detection tests using both a converter transformer partial discharge propagation characteristic test platform and a conventional partial discharge detection unit.

[0023] Step S5; Perform a partial discharge detection anti-interference test on the transformer, specifically as follows:

[0024] A periodic narrowband interference signal is input to the transformer body using a signal generator. A converter transformer partial discharge anti-interference test platform and a conventional partial discharge detection unit are used to perform partial discharge detection anti-interference test on the transformer body with the periodic narrowband interference signal.

[0025] Compared with existing technologies, the present invention has the following advantages: The present invention achieves the separation of partial discharge pulse current signals by using two symmetrically arranged balanced impedances in a state where the impedance core is close to zero magnetic flux, eliminating the need to use two similar samples for testing, simplifying the test wiring, and also having superior anti-interference performance. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the partial discharge detection and testing platform structure in Embodiment 1 of the present invention.

[0027] Figure 2 This is a schematic diagram of the transformer body structure according to Embodiment 1 of the present invention.

[0028] Figure 3 This is a schematic diagram of the detection unit structure in Embodiment 1 of the present invention.

[0029] Figure 4 This is a schematic diagram of the results of the partial discharge detection anti-interference test platform in Embodiment 1 of the present invention.

[0030] Figure 5 This is a schematic diagram of the planar structure of the partial discharge test results in Embodiment 2 of the present invention.

[0031] Figure 6 This is a schematic diagram of the planar structure of the partial discharge waveform measured by the conventional partial discharge detection method of the present invention.

[0032] Figure 7 This is a schematic diagram of the partial discharge waveform planar structure measured by the method in Embodiment 2 of the present invention.

[0033] In the diagram: 1. Transformer body; 11. Oil tank; 111. Observation window; 12. Grid-side bushing; 13. First valve-side bushing; 14. Second valve-side bushing; 15. Grid-side winding; 151. Tap; 16. Valve-side winding; 2. Pressurization unit; 3. Detection unit; 31. Input module; 311. Shielding box; 312. First balancing winding; 313. Second balancing winding; 32. Partial discharge detector; 4. Current-limiting reactor; 5. Voltage divider; 6. Signal generator; 7. Partial discharge generation unit; 71. Fixing plate; 711. Contact; 72. Connecting bracket; 73. Adjusting plate; 74. Discharge needle; T is magnetic core; N3 is detection winding; R is detection resistor; BNC is BNC terminal; C is coupling capacitor. Detailed Implementation

[0034] Example 1

[0035] like Figure 1-7As shown in the figure, the present invention provides a technical solution: a converter transformer partial discharge test platform based on the single-unit balance method, comprising a transformer body 1, a pressurizing unit 2, and a detection unit 3. The transformer body 1 includes an oil tank 11, and a grid-side bushing 12, a first valve-side bushing 13, and a second valve-side bushing 14 are provided on the outside of the oil tank 11. The pressurizing unit 2 and the detection unit 3 are connected in parallel between the first valve-side bushing 13 and the second valve-side bushing 14 of the oil tank 11. The detection unit 3 includes an input module 31 and a partial discharge detector 32. The input module 31 includes a shielded box. 311, a magnetic core is installed inside the shielding box 311. A first balancing winding 312, a second balancing winding 313 and a detection winding are wound on the magnetic core. The first balancing winding 312 and the second balancing winding 313 are arranged symmetrically and crosswise. The end of the first balancing winding 312 is connected to the beginning of the second balancing winding 313 and grounded. The beginning of the first balancing winding 312 is electrically connected to the first valve side bushing 13 of the oil tank 11 through a coupling capacitor. A detection resistor is connected in parallel to both ends of the detection winding. The detection resistor is connected to a partial discharge detector 32 through a terminal.

[0036] Furthermore, a shielding layer is provided on the outside of the magnetic core and the detection winding.

[0037] Furthermore, the oil tank 11 also includes a grid-side winding 15 and a valve-side winding 16. The grid-side winding 15 and the valve-side winding 16 are provided inside the oil tank 11. The high-voltage end of the grid-side winding 15 is electrically connected to the grid-side bushing 12, and the low-voltage end of the grid-side winding 15 is grounded. The two terminals of the valve-side winding 16 are electrically connected to the first valve-side bushing 13 and the second valve-side bushing 14, respectively. The grid-side winding 15 is provided with five taps 151.

[0038] The detailed parameters of transformer body 1 are shown in the table below;

[0039]

[0040] Furthermore, a partial discharge generating unit 7 is installed on the oil tank 11. The partial discharge generating unit 7 includes a fixing plate 71 and contacts 711. An insulating fixing plate 71 is vertically installed inside the oil tank 11. Five contacts 711 are evenly arranged on the fixing plate 71 along the vertical direction. The number of five taps 151 of the wire side winding 15 is equal to the number of five contacts 711 of the fixing plate 71. The five taps 151 are electrically connected to the contacts 711 one by one. The bottom contact 711 can be a screw. The five bottom contacts 711 are Y5, Y4, Y3, Y2 and Y1 from top to bottom.

[0041] Furthermore, the partial discharge generating unit 7 also includes a connecting bracket 72, an adjusting plate 73, and a discharge needle 74; the adjusting plate 73 is movably mounted on the oil tank 11, the adjusting plate 73 is vertically mounted on the oil tank 11, and the discharge needle 74 is mounted on the adjusting plate 73. The adjusting plate 73 moves back and forth in the vertical direction, and the discharge needle 74 corresponds to different contacts 711; the top of the oil tank 11 has an opening, and the connecting bracket 72 is welded to the opening at the top of the oil tank 11. The connecting bracket 72 has several connecting holes, which are horizontally arranged on the connecting bracket 72. The adjusting plate 73 is inserted into the top opening of the oil tank 11. The adjusting plate 73 has five adjusting holes, the number of which is equal to the number of five contacts 711 on the fixed plate 71. The distance between adjacent adjusting holes is equal to the distance between adjacent contacts 711. The adjusting holes on the adjusting plate 73 are connected to the connecting holes on the connecting bracket 72 by a pin. When different adjusting holes on the adjusting plate 73 are connected to the connecting holes on the connecting bracket 72 by a pin, the anti-electric needle 74 corresponds to different contacts 711, thereby changing the location where partial discharge occurs.

[0042] Furthermore, an observation window 111 is installed and connected to the side of the oil tank 11; the observation window 111 is located at the partial discharge generation unit 7, thereby enabling the observation of partial discharge.

[0043] Furthermore, a current-limiting reactor 4 and a voltage divider 5 are electrically connected at the grid-side bushing 12 of the oil tank 11; the current-limiting reactor 4 can limit the current in the event of breakdown, protecting the transformer body 1 from damage; the voltage divider 5 can monitor the voltage value at the grid-side bushing 12 in real time, which is convenient for recording the voltage data of partial discharge, and can be safely and reliably grounded.

[0044] Furthermore, a signal generator 6 is electrically connected to the grid-side bushing 12 of the oil tank 11. During the partial discharge detection anti-interference test, the grid-side bushing 12 is also electrically connected to the signal generator 6. The signal generator 6 is used to simulate various noise interferences that occur in the converter transformer field. The DG1000Z signal generator is selected. The DG1000Z signal generator has two signal output ports and can simulate the situation where multiple noise interferences exist in the converter transformer field. In addition to outputting general sine signals and Gaussian noise signals, it can also output arbitrary signal waveforms with frequencies from 1kHz to 20MHz to meet the needs of actual engineering.

[0045] Example 2

[0046] A method for testing partial discharge of converter transformers based on the single-unit balancing method, comprising the following steps:

[0047] Step S1: Set up two converter transformer partial discharge test platforms;

[0048] The two converter transformer partial discharge test platforms are divided into a converter transformer partial discharge propagation characteristic test platform and a converter transformer partial discharge anti-interference test platform.

[0049] The two converter transformer partial discharge test platforms include a calibration pulse generator, a transformer body, a detection unit, a partial discharge calibrator, a grid-side bushing, an oscilloscope, an input module, and a signal generator.

[0050] Step S2: Partial discharge quantity calibration, specifically:

[0051] By inputting a known charge Q0 = U0C0 from the grid-side bushing into the transformer body through a calibration pulse generator, the detection unit response is L'. After removing the calibration pulse generator and conducting a voltage test, when the transformer body discharges internally, the detection unit response is L. From this, the conversion factor K can be obtained. h =L / L′;

[0052] The apparent discharge quantity Q is then:

[0053] Q=U0C0K h ;

[0054] In the formula, Q represents the apparent discharge quantity, pC;

[0055] Among them, C0 must satisfy;

[0056]

[0057] C0 > 10pF;

[0058] In the formula, C x This indicates a test sample identical to the test capacitor C, where C represents the test capacitor. m This represents the equivalent capacitance across the input module.

[0059] The apparent discharge quantity can be linked to the measured pulse voltage amplitude by using a conversion factor. The partial discharge calibrator is connected in parallel with the transformer body, and the output of the partial discharge calibrator is adjusted to different discharge quantities. The amplitude of the pulse voltage at both ends of the input module is recorded simultaneously using an oscilloscope, and the relationship between the pulse voltage amplitude U0 and the apparent discharge quantity Q is plotted.

[0060] Step S3: Determine the initial discharge voltage and the test voltage, specifically as follows:

[0061] Slowly increase the voltage input to the transformer body. When a partial discharge signal is observed at the detection unit, stop increasing the voltage and record the voltage value at the grid-side bushing at this time.

[0062] The initiation discharge voltage does not need to be observed as a stable pulse waveform. As long as there is a waveform that matches the characteristics of a partial discharge pulse, it can be considered that a partial discharge has occurred.

[0063] After five initial discharge voltage tests at each partial discharge location, the average initial discharge voltage was obtained by plotting a Weibull distribution diagram. Under the condition that partial discharge could occur at all locations, subsequent test voltages were selected, and the selected test voltages were all higher than the average initial voltage of the discharge location.

[0064] Step S4: Perform partial discharge detection test on the transformer, specifically as follows:

[0065] Partial discharge detection was performed on the transformer body using the single-unit balance method of the converter transformer partial discharge propagation characteristic test platform in step S1 and the conventional method of the conventional partial discharge detection unit. The partial discharge locations for this partial discharge detection test were selected at three positions on the transformer body: Y4, Y3, and Y2. The same experimental voltage level was used for both methods, and the signal fluctuations during discharge were recorded.

[0066] like Figure 5 The individual unit balancing method of the converter transformer partial discharge propagation characteristic test platform and the conventional method of the conventional partial discharge detection unit were used to perform partial discharge detection at three positions Y4, Y3 and Y2 of the transformer body. The time domain waveforms of the individual unit balancing method and the conventional method were obtained respectively.

[0067] Analysis of the time-domain waveforms shows that the partial discharge signal waveforms measured by the two methods are highly similar. The amplitude of the signal waveform measured by the single-unit balance method of the converter transformer partial discharge propagation characteristic test platform is 0.092V, while the amplitude of the signal waveform measured by the conventional method of the conventional partial discharge detection unit is 0.121V, which is 31.52% different from the former. This is because some noise interference is unavoidable in the experimental procedure. The single-unit balance method has a noise suppression effect, and there are also measurement errors in the experiment. Therefore, there will be some difference between the amplitude of the signal waveform measured by the single-unit balance method and the amplitude of the signal waveform measured by the conventional method, but it is still within the normal range.

[0068] As the discharge location moves downwards, the amplitude gradually decreases. The waveform amplitude measured by the single-unit balance method of the converter transformer partial discharge propagation characteristic test platform increases by 0.004V from 0.092V at Y4 to 0.096V at Y2, representing a 4.34% increase compared to Y4. Theoretically, the signal amplitude measured at symmetrical winding locations during partial discharge is the same, the polarity of the first wave is opposite, and they are symmetrical about the 0 axis. However, this is almost impossible to achieve in actual engineering, hence the slight error is consistent with reality. The conventional method of the conventional partial discharge detection unit measures a signal amplitude of 0.093V at Y2, which decreases by 23.14% during this process. The amplitude of the partial discharge signal continues to decrease as the partial discharge location moves downwards.

[0069] The corresponding frequency domain waveforms show that the frequency domain waveforms of the two methods are consistent. The partial discharge signals detected by the single-unit balance method of the converter transformer partial discharge propagation characteristic test platform and the conventional method of the conventional partial discharge detection unit are extremely similar in the time domain. This proves that the single-unit balance method of the converter transformer partial discharge propagation characteristic test platform can effectively detect transformer partial discharge signals and can sensitively reflect small changes in partial discharge signals. It is suitable for engineering applications in the field of converter transformer partial discharge test.

[0070] Step S5 involves performing an anti-interference test for partial discharge detection of the transformer, specifically as follows:

[0071] Partial discharge signals generally have very low energy. When the received signal contains strong noise, the noise will seriously affect the analysis results.

[0072] A signal generator is used to output a white noise interference signal with a bandwidth of 60MHz and a periodic narrowband interference signal with a frequency of 100kHz to the transformer body, respectively.

[0073] like Figure 6 The conventional method of using a conventional partial discharge detection unit is used to detect partial discharge at three locations Y4, Y3 and Y2 of the transformer body with periodic narrowband interference signals, and the time domain waveform and the corresponding frequency domain waveform are obtained respectively.

[0074] Analysis of the time-domain waveforms reveals certain similarities in periodic trends and oscillation ranges, but the partial discharge signal cannot be directly extracted. Analysis of the frequency-domain waveforms shows peak values ​​around 100kHz, but numerous harmonic peaks (white noise interference) exist in the 0-4MHz range. Due to the symmetry of the single-unit balancing method of the converter transformer partial discharge interference test platform, the polarity of the first wave of the signal measured when partial discharge occurs at Y2 is opposite to that at Y4. Furthermore, the time-domain waveform of the measured signal also exhibits symmetry about the 0 axis when partial discharge occurs at symmetrical winding positions. Therefore, after partial discharge occurs at the absolute neutral point of the winding, the partial discharge signal measured by the single-unit balancing method of the converter transformer partial discharge interference test platform is zero. However, this condition is difficult to achieve; during the experiment, the location of the partial discharge can be determined by analyzing the polarity and amplitude of the first wave of the partial discharge signal.

[0075] like Figure 7 The individual balance method of the converter transformer partial discharge anti-interference test platform was used to detect partial discharge at three positions Y4, Y3 and Y2 of the transformer winding with periodic narrowband interference signal, and the time domain waveform and the corresponding frequency domain waveform were obtained respectively.

[0076] At this time, under the interference suppression of the single-unit balance method of the converter transformer partial discharge interference suppression test platform, the amplitude of the periodic oscillation is greatly reduced, and various characteristics of the time-domain waveform obtained by the partial discharge test at Y4-Y2 can be clearly seen, such as the polarity of the first wave, the signal peak value and the duration of the partial discharge pulse.

[0077] Analysis of the frequency domain waveform shows that a spike still exists around 100kHz, indicating that periodic narrowband interference is still present in the signal, but its amplitude is greatly reduced. Compared to the peak values ​​of the frequency domain waveform of the partial discharge signal measured by conventional methods using conventional partial discharge detection units, these peak values ​​are much smaller. Figure 6 In comparison, the frequency domain waveform of partial discharge signals is easier to detect and extract. This proves that under complex test conditions, the single-unit balancing method of the converter transformer partial discharge anti-interference test platform can still effectively suppress the interference in the environment and accurately measure the partial discharge signal. Compared with the discharge detection method of conventional partial discharge detection units, the single-unit balancing method of the converter transformer partial discharge anti-interference test platform can play an important role in the partial discharge field of converter transformers.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A converter transformer partial discharge test platform based on the single-unit balancing method, comprising a transformer body (1), a voltage application unit (2), and a detection unit (3), characterized in that, The transformer body (1) includes an oil tank (11). A grid-side bushing (12), a first valve-side bushing (13), and a second valve-side bushing (14) are provided on the outside of the oil tank (11). A pressurization unit (2) and a detection unit (3) are connected in parallel between the first valve-side bushing (13) and the second valve-side bushing (14) of the oil tank (11). The detection unit (3) includes an input module (31) and a partial discharge detector (32). The input module (31) includes a shielded box (311). A magnetic core is installed inside the shielded box (311), and the magnetic core is wound with... The device is provided with a first balancing winding (312), a second balancing winding (313) and a detection winding. The first balancing winding (312) and the second balancing winding (313) are arranged symmetrically and crosswise. The end of the first balancing winding (312) is connected to the beginning of the second balancing winding (313) and grounded. The beginning of the first balancing winding (312) is electrically connected to the first valve side bushing (13) of the oil tank (11) through a coupling capacitor. A detection resistor is connected in parallel at both ends of the detection winding. The detection resistor is connected to a partial discharge detector (32) through a terminal.

2. The converter transformer partial discharge test platform based on the single-unit balancing method according to claim 1, characterized in that: The magnetic core and the detection winding are provided with a shielding layer on the outside.

3. The converter transformer partial discharge test platform based on the single-unit balancing method according to claim 2, characterized in that: The oil tank (11) also includes a mesh-side winding (15) and a valve-side winding (16). The mesh-side winding (15) and the valve-side winding (16) are provided inside the oil tank (11). The high-voltage end of the mesh-side winding (15) is electrically connected to the mesh-side bushing (12), and the low-voltage end of the mesh-side winding (15) is grounded. The two terminals of the valve-side winding (16) are electrically connected to the first valve-side bushing (13) and the second valve-side bushing (14) respectively. The mesh-side winding (15) is provided with multiple taps (151).

4. The converter transformer partial discharge test platform based on the single-unit balancing method according to claim 3, characterized in that: The oil tank (11) is equipped with a partial discharge generating unit (7). The partial discharge generating unit (7) includes a fixing plate (71) and contacts (711). The fixing plate (71) of insulating material is vertically installed inside the oil tank (11). Multiple contacts (711) are evenly arranged on the fixing plate (71) along the vertical direction. The number of multiple taps (151) of the wire side winding (15) is equal to the number of multiple contacts (711) of the fixing plate (71). The multiple taps (151) are electrically connected to the contacts (711) one by one.

5. The converter transformer partial discharge test platform based on the single-unit balancing method according to claim 4, characterized in that: The partial discharge generating unit (7) further includes a connecting bracket (72), an adjusting plate (73), and a discharge needle (74); the adjusting plate (73) is movably mounted on the oil tank (11), the adjusting plate (73) is vertically mounted on the oil tank (11), the discharge needle (74) is mounted on the adjusting plate (73), the adjusting plate (73) moves back and forth in the vertical direction, and the discharge needle (74) corresponds to different contacts (711); the top of the oil tank (11) has an opening, and a connecting bracket is welded to the opening at the top of the oil tank (11). (72) The connecting bracket (72) has several connecting holes, which are horizontally arranged on the connecting bracket (72). The adjusting plate (73) is inserted into the top opening of the oil tank (11). The adjusting plate (73) has multiple adjusting holes, the number of which is equal to the number of contacts (711) on the fixed plate (71). The distance between adjacent adjusting holes is equal to the distance between adjacent contacts (711). The adjusting holes on the adjusting plate (73) and the connecting holes on the connecting bracket (72) are connected by a pin.

6. The converter transformer partial discharge test platform based on the single-unit balancing method according to claim 5, characterized in that: An observation window (111) is installed on the side of the oil tank (11).

7. The converter transformer partial discharge test platform based on the single-unit balancing method according to claim 6, characterized in that: The oil tank (11) is electrically connected to a current-limiting reactor (4) and a voltage divider (5) at the mesh side bushing (12).

8. The converter transformer partial discharge test platform based on the single-unit balancing method according to claim 7, characterized in that: A signal generator (6) is electrically connected to the mesh side sleeve (12) of the oil tank (11).

9. A method for testing partial discharge of converter transformers based on the single-unit balancing method, characterized in that, The steps include the following: Step S1: Set up two converter transformer partial discharge test platforms; The two converter transformer partial discharge test platforms are divided into a converter transformer partial discharge propagation characteristic test platform and a converter transformer partial discharge anti-interference test platform. Step S2: Partial discharge quantity calibration, specifically: A known charge Q0 = U0C0 is injected into the transformer body from the grid-side bushing using a calibration pulse generator, and the detection unit responds with L'. The calibration pulse generator is then removed, and a voltage test is performed. When the transformer body discharges internally, the detection unit responds with L, yielding the conversion factor K. h =L / L′, using the obtained conversion factor K h The apparent discharge quantity is obtained by adding the pulse voltage amplitude U0 and the series small capacitor C0; then, the apparent discharge quantity is obtained by using the conversion factor K. h The apparent discharge quantity is correlated with the measured pulse voltage amplitude. The partial discharge calibrator is connected to the transformer body. The output of the partial discharge calibrator is adjusted to different discharge quantities. The relationship between the pulse voltage amplitude and the apparent discharge quantity is plotted. In the formula, Q0 represents the charge, U0 represents the pulse voltage amplitude, V, C0 represents the series small capacitor, pF, K h Indicates the conversion factor; Step S3: Determine the initial discharge voltage and the test voltage, specifically as follows: The voltage input to the transformer body is slowly increased. After five initial discharge voltage tests at each partial discharge location, the average value of the initial discharge voltage is obtained by plotting a Weibull distribution diagram. Under the condition that partial discharge can occur at all locations, subsequent test voltages are selected, and the selected test voltages are all higher than the average value of the initial voltage at that discharge location. Step S4: Perform partial discharge detection test on the transformer, specifically as follows: The transformer body was subjected to partial discharge detection tests using both a converter transformer partial discharge propagation characteristic test platform and a conventional partial discharge detection unit. Step S5; Perform a partial discharge detection anti-interference test on the transformer, specifically as follows: A periodic narrowband interference signal is input to the transformer body using a signal generator. A converter transformer partial discharge anti-interference test platform and a conventional partial discharge detection unit are used to perform partial discharge detection anti-interference test on the transformer body with the periodic narrowband interference signal.

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