Method for testing deterioration of insulation of high-voltage bushing superimposed with high-frequency voltage and control device

Abstract

The application provides a high-voltage bushing insulation deterioration test method and control device superimposed with high-frequency voltage, and the method comprises the following steps: determining the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage and the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage; installing two test bushings to a test loop and a control loop, controlling the voltage source in the test loop to be raised to the equivalent effective value of the composite voltage, ensuring that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage is constant, and synchronously controlling the voltage source in the control loop to be raised to the equivalent effective value of the steady-state voltage; synchronously performing insulation deterioration comparative tests on the two test bushings and collecting the insulation performance parameters of the two test bushings, and then analyzing the insulation deterioration difference under the steady-state voltage and the composite voltage. The application can simulate the composite electric field environment of the superimposition of the power frequency / DC steady-state voltage and the high-frequency harmonic voltage, and accurately analyze the insulation deterioration difference under the steady-state voltage and the composite voltage.

Description

Technical Field

[0001] This invention relates to the field of high-voltage power equipment testing technology, and more specifically, to a method and control device for testing the insulation degradation of high-voltage bushings by superimposing high-frequency voltage. Background Technology

[0002] With the large-scale application of flexible DC transmission, new energy grid connection, and power electronic equipment, grid voltage distortion has intensified. High-voltage DC / power frequency combined with high-frequency harmonics has become a typical operating condition for power equipment such as bushings and dry-type transformers. The impact of high-frequency harmonics on the operational reliability of critical equipment is becoming increasingly prominent. Existing research mainly focuses on the insulation degradation / aging patterns under DC, power frequency, lightning impulse, and high-frequency pulse conditions. There are significant shortcomings in the relevant fundamental theories, which restricts the safe design and application of equipment insulation under harmonic conditions.

[0003] In recent years, the Shizhou and Yichang converter stations of the Chongqing-Hubei Flexible DC Transmission Project have experienced multiple insulation breakdown faults in the through-wall bushings of the bridge arms, causing project shutdowns and significant losses. On-site measurements at the flexible DC transmission project site revealed that the through-wall bushings, in addition to bearing conventional power frequency and DC voltages, were simultaneously subjected to high-frequency voltages, multiples of 10kHz and reaching up to several hundred kHz. The resulting final screen current amplitude in the bushing capacitor core reached tens of amperes, approximately a hundred times higher than that of a conventional AC system. The superimposed high-frequency voltage reduces the insulation strength of the bushing material and increases dielectric loss and heat generation within the bushing core, leading to an increase in bushing operating temperature. These two factors interact, posing a severe challenge to the long-term operational reliability of the bushings. Therefore, it is urgent to study the impact of superimposed high-frequency voltage on the bushing insulation performance and clarify the differences in the insulation degradation patterns under conventional DC / power frequency voltage and superimposed high-frequency voltage conditions.

[0004] Through a review of existing technologies and verification through engineering applications, the existing high-voltage bushing insulation degradation testing technologies have the following main shortcomings, which restrict the development of bushing insulation degradation testing and mechanism research: 1. Poor simulation of operating conditions: High-voltage bushings are in a composite electric field environment of power frequency / DC steady-state voltage superimposed with high-frequency harmonic voltage. However, the existing single voltage test method cannot achieve synchronous superposition output of DC / power frequency working voltage and high-frequency disturbance voltage, making it difficult to simulate the composite voltage condition of "power frequency steady state + high-frequency disturbance" in actual power grid operation. This results in a large deviation between the test degradation mechanism and the actual degradation mechanism on site, and the test results have low reference value.

[0005] 2. Lack of a comparative test system: Existing tests do not support simultaneous comparative testing of benchmark tests and composite tests. It is impossible to intuitively compare the differences in insulation degradation under pure DC, pure power frequency and superimposed high frequency composite conditions under completely consistent operating conditions, environment and parameters. The ability to compare and analyze degradation mechanisms and quantitatively assess the impact of disturbances is lacking.

[0006] 3. Inaccurate matching of voltage equivalence: Existing test equipment lacks a precise coordinated control module for voltage amplitude and frequency. After the power frequency / DC steady-state voltage is superimposed with the high-frequency voltage, the total effective value of the voltage will increase significantly, resulting in inconsistent voltage energy input between the reference condition and the composite condition. There is no coordinated closed-loop control during the voltage boosting process, which easily leads to problems such as voltage ratio deviation and excessive effective value deviation. It is impossible to guarantee the test conditions of a single variable, and there are systematic errors in the comparative test data.

[0007] 4. Insulation degradation mechanism analysis cannot be quantitatively analyzed: Traditional tests can only complete aging induction tests and cannot collect key insulation parameters such as bushing dielectric loss, partial discharge, insulation resistance, and leakage current in real time. They cannot achieve dynamic monitoring of the degradation process and quantitative analysis of degradation characteristics, making it difficult to support in-depth analysis of insulation degradation mechanism. Summary of the Invention

[0008] In view of this, the present invention proposes a high-voltage bushing insulation degradation test method using superimposed high-frequency voltage, aiming to solve the problem that existing technologies cannot accurately determine the differences in bushing insulation degradation patterns under DC / power frequency voltage superimposed with high-frequency voltage. The present invention also proposes a control device for the high-voltage bushing insulation degradation test using the superimposed high-frequency voltage method.

[0009] In one aspect, the present invention proposes a method for testing the insulation degradation of high-voltage bushings under superimposed high-frequency voltage. The method includes the following steps: a determination step, determining the test conditions and the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, as well as the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage; wherein the equivalent effective value of the composite voltage is equal to the equivalent effective value of the steady-state voltage, the steady-state voltage is a power frequency voltage or DC voltage, and the composite voltage is the voltage obtained by superimposing the high-frequency voltage on the steady-state voltage; a control step, installing two pre-selected test bushings into the test circuit and the control circuit respectively, controlling the voltage value of the voltage source in the test circuit to increase to the equivalent effective value of the composite voltage, and ensuring that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage remains constant, and simultaneously controlling the voltage value of the voltage source in the control circuit to increase to the equivalent effective value of the steady-state voltage; a test step, simultaneously conducting insulation degradation comparison tests on the two test bushings and collecting the insulation performance parameters of the two test bushings; and an analysis step, analyzing the differences in insulation degradation under steady-state voltage and composite voltage based on the insulation performance parameters of the two test bushings.

[0010] Furthermore, in the above-mentioned high-voltage bushing insulation degradation test method with superimposed high-frequency voltage, the determination step involves determining the effective value of the steady-state component voltage, the effective value of the high-frequency component voltage, the frequency and peak value of the high-frequency component voltage, and the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, based on the measured waveform, simulated waveform, or research requirements.

[0011] Furthermore, in the above-mentioned high-voltage bushing insulation degradation test method with superimposed high-frequency voltage, for the measured waveform or simulated waveform, the effective value of the steady-state component voltage, the effective value of the high-frequency component voltage, the frequency and peak value of the high-frequency component voltage are calculated based on the waveform, and the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage is calculated based on the effective value of the steady-state component voltage and the effective value of the high-frequency component voltage in the composite voltage, or the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage is set according to the research requirements.

[0012] Furthermore, in the above-mentioned high-voltage bushing insulation degradation test method with superimposed high-frequency voltage, when the steady-state voltage is the power frequency voltage, according to the formula... Calculate the equivalent effective value of the composite voltage U total In the formula, U ac ＇ This represents the effective value of the power frequency component voltage in the composite voltage. U h This represents the peak value of the high-frequency component in the composite voltage; when the steady-state voltage is a DC voltage, according to the formula... Calculate the equivalent effective value of the composite voltage U total In the formula, U dc ＇ This represents the effective value of the DC component voltage in the composite voltage. U h This represents the peak value of the high-frequency component of the composite voltage.

[0013] Furthermore, in the above-mentioned high-voltage bushing insulation degradation test method with superimposed high-frequency voltage, in the control step, the voltage values ​​of the voltage sources in the test circuit and the control circuit are synchronously controlled to increase based on the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, the frequency of the high-frequency component voltage, the equivalent effective value of the composite voltage, and the equivalent effective value of the steady-state voltage; during the increase process, the voltage boosting rate of the voltage sources in the test circuit and the control circuit is dynamically controlled based on the waveforms of the collected composite voltage and steady-state voltage.

[0014] Furthermore, the above-mentioned high-voltage bushing insulation degradation test method with superimposed high-frequency voltage includes, before the determination step, the following steps: selecting two test bushings with identical parameters and pre-treating the two test bushings; in the determination step, determining the test conditions based on the type of the selected test bushing, and determining the voltage sources of the test circuit and the control circuit based on the test conditions; wherein, the test conditions include: insulation degradation comparison test of power frequency superimposed high-frequency voltage and power frequency voltage and insulation degradation comparison test of DC superimposed high-frequency voltage and DC voltage; for the insulation degradation comparison test of power frequency superimposed high-frequency voltage and power frequency voltage, the voltage source of the test circuit includes: power frequency high-voltage power supply and high-frequency high-voltage power supply, and the voltage source of the control circuit is power frequency high-voltage power supply; for the insulation degradation comparison test of DC superimposed high-frequency voltage and DC voltage, the voltage source of the test circuit includes: DC high-voltage power supply and high-frequency high-voltage power supply, and the voltage source of the control circuit is DC high-voltage power supply.

[0015] Furthermore, in the above-mentioned high-voltage bushing insulation degradation test method with superimposed high-frequency voltage, in the analysis step, when the parameters of any test bushing reach the failure threshold, the voltage output of the corresponding circuit is stopped, the curve of the insulation parameters changing with the test duration is plotted, and the insulation degradation acceleration mechanism is analyzed.

[0016] This invention enables a direct comparison of the degradation differences between pure power frequency / DC steady-state voltage and high-frequency superimposed composite voltage. When increasing the voltage source of the test and control circuits, it ensures that the equivalent effective value of the increased steady-state voltage is equal to the equivalent effective value of the composite voltage, and maintains a constant ratio between the effective values ​​of the steady-state and high-frequency components of the composite voltage. This ensures coordinated control during the voltage boosting process, thereby guaranteeing the authenticity, comparability, and accuracy of the test. It allows for accurate analysis of the insulation degradation differences under steady-state and composite voltages, providing reliable experimental support for high-voltage bushing insulation performance evaluation, research on differentiated degradation mechanisms under high-frequency disturbances, and service life prediction. This solves the problem that existing technologies cannot accurately determine the differences in bushing insulation degradation patterns under DC / power frequency voltage superimposed with high-frequency voltage.

[0017] On the other hand, the present invention also proposes a control device for high-voltage bushing insulation degradation test using any of the above-mentioned high-voltage bushing insulation degradation test methods with superimposed high-frequency voltage. This device includes: a control system, a test circuit voltage source, a control circuit voltage source, an insulation parameter measuring device, and an analysis system. The control system is electrically connected to both the test circuit voltage source and the control circuit voltage source, and is used to pre-set the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, as well as the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage. Based on the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, the control system controls the voltage value of the test circuit voltage source to increase to the equivalent effective value of the composite voltage, and simultaneously controls the voltage value of the control circuit voltage source to increase to the equivalent effective value of the steady-state voltage. The insulation parameter measuring device is used to measure the insulation performance parameters of the test bushing in the test circuit and the control circuit, respectively. The analysis system is electrically connected to the insulation parameter measuring device and is used to analyze the difference in insulation degradation under regulated voltage and composite voltage based on the insulation performance parameters of the test bushing in the test circuit and the control circuit.

[0018] Furthermore, the aforementioned high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage also includes: a composite voltage measurement module and a steady-state voltage measurement module; wherein, the composite voltage measurement module is used to measure the composite voltage waveform borne by the test bushing in the test circuit; the steady-state voltage measurement module is used to measure the steady-state voltage waveform borne by the test bushing in the control circuit; the control system is electrically connected to both the composite voltage measurement module and the steady-state voltage measurement module, and is used to dynamically adjust the boost rate of the voltage source of the test circuit and the voltage source of the control circuit according to the composite voltage waveform and the steady-state voltage waveform.

[0019] Furthermore, in the aforementioned high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage, when the test bushing is subjected to a power frequency superimposed high-frequency voltage, the control circuit voltage source is a power frequency high-voltage power supply; the test circuit voltage source includes: a high-frequency high-voltage power supply and a power frequency high-voltage power supply connected in parallel; when the test bushing is subjected to a DC superimposed high-frequency voltage, the control circuit voltage source is a DC high-voltage power supply; the test circuit voltage source includes: a high-frequency high-voltage power supply and a DC high-voltage power supply connected in parallel; the high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage also includes: a low-frequency voltage isolation module and a high-frequency voltage isolation module; wherein, the low-frequency voltage isolation module is set in the test circuit and connected in series with the high-frequency high-voltage power supply; the high-frequency voltage isolation module is set in the test circuit and connected in series with either the power frequency high-voltage power supply or the DC high-voltage power supply.

[0020] Since the high-voltage bushing insulation degradation test method with superimposed high-frequency voltage has the above-mentioned effects, the high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage corresponding to the test method also has the corresponding technical effects. Attached Figure Description

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart of a high-voltage bushing insulation degradation test method with superimposed high-frequency voltage provided in an embodiment of the present invention; Figure 2 Another flowchart of the high-voltage bushing insulation degradation test method with superimposed high-frequency voltage provided in the embodiments of the present invention; Figure 3 This is a schematic diagram of the structure of the high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage provided in an embodiment of the present invention; Figure 4 The output waveform is a composite voltage of power frequency and high frequency. Figure 5 The output waveform is a DC superimposed high-frequency composite voltage. Figure 6 Typical partial discharge patterns of bushings at power frequency; Figure 7 This is a typical partial discharge pattern of a bushing under power frequency superimposed with high-frequency harmonics. Detailed Implementation

[0022] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] Method Implementation Examples: See Figure 1 , Figure 1 A flowchart of the high-voltage bushing insulation degradation test method with superimposed high-frequency voltage provided in this embodiment of the invention. As shown in the figure, the high-voltage bushing insulation degradation test method with superimposed high-frequency voltage includes the following steps: Step S1 is defined to determine the test conditions and the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, as well as the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage. The equivalent effective value of the composite voltage is equal to the equivalent effective value of the steady-state voltage, the steady-state voltage is the power frequency voltage or DC voltage, and the composite voltage is the voltage obtained by superimposing the high-frequency voltage on the steady-state voltage.

[0024] Specifically, when the steady-state voltage is the power frequency voltage, the composite voltage is the voltage after the power frequency voltage is superimposed with the high-frequency voltage. The effective value of the steady-state component voltage is the effective value of the power frequency component voltage, and the equivalent effective value of the steady-state voltage is the equivalent effective value of the power frequency voltage.

[0025] When the steady-state voltage is a DC voltage, the composite voltage is the voltage obtained by superimposing a high-frequency voltage onto the DC voltage. The effective value of the steady-state component voltage is the effective value of the DC component voltage, and the effective value of the steady-state voltage is the effective value of the DC voltage.

[0026] When conducting the test, it is first necessary to select two sample sleeves and determine the test conditions based on the type of sample sleeve. That is, see [link to relevant documentation]. Figure 2 Before determining step S1, the following may also be included: Select step S5, select two sample sleeves with the same parameters, and pre-treat the two sample sleeves.

[0027] Specifically, the two selected test bushings were products from the same batch, of the same specification, and of the same design, with identical materials, structure, and initial insulation performance parameters. The two test bushings were used in the test group and the control group, respectively. In the test group, a composite voltage consisting of a steady-state voltage and a high-frequency voltage was applied to the test bushings. In the control group, a steady-state voltage was applied to the test bushings. The steady-state voltage was either a power frequency voltage or a DC voltage.

[0028] The pretreatment of the test bushings specifically involves: visual inspection, cleaning, and drying of the two selected test bushings to remove surface stains and moisture, avoid external interference, and fixing the test bushings in the insulation test position. High-voltage wiring, grounding wiring, and the installation and calibration of all testing sensors are then completed to ensure reliable wiring insulation and that sensor sampling accuracy meets standards. The two test bushings are then installed in the test circuit of the test group and the control circuit of the control group, respectively, for insulation degradation testing.

[0029] In step S1, the test conditions are determined based on the type of the selected test sleeve, and the voltage sources for the test circuit and the control circuit are determined based on the test conditions.

[0030] Specifically, the test conditions include: a comparative test of insulation degradation between power frequency superimposed high-frequency voltage and power frequency voltage, and a comparative test of insulation degradation between DC superimposed high-frequency voltage and DC voltage. The comparative test of insulation degradation between power frequency superimposed high-frequency voltage and power frequency voltage is conducted on bushings subjected to power frequency superimposed high-frequency voltage (such as the AC side bridge arm wall bushing of a flexible DC system), and this test can be designated as condition 1. The comparative test of insulation degradation between DC superimposed high-frequency voltage and DC voltage is conducted on bushings subjected to DC superimposed high-frequency voltage (such as the DC side pole line wall bushing), and this test can be designated as condition 2.

[0031] For the insulation degradation comparison test between power frequency superimposed high-frequency voltage and power frequency voltage (i.e., operating condition 1), two sets of power frequency high-voltage power supplies and one set of high-frequency high-voltage power supply are used. The voltage source of the test circuit includes one set of power frequency high-voltage power supply and one set of high-frequency high-voltage power supply. The power frequency superimposed high-frequency composite voltage generated by the power frequency high-voltage power supply and the high-frequency high-voltage power supply is used to carry out the insulation degradation test on the test bushing. The voltage source of the control circuit is one set of power frequency high-voltage power supply. The insulation degradation comparison test under steady-state pure power frequency voltage is carried out on the test bushing using the power frequency high-voltage power supply.

[0032] For the insulation degradation comparison test between DC superimposed high-frequency voltage and DC voltage (i.e., operating condition 2), two sets of DC high-voltage power supplies and one set of high-frequency high-voltage power supply are used. The voltage source of the test circuit includes one set of DC high-voltage power supply and one set of high-frequency high-voltage power supply. The DC superimposed high-frequency composite voltage generated by the DC high-voltage power supply and the high-frequency high-voltage power supply is used to conduct the insulation degradation test on the test bushing under steady-state pure DC voltage. The voltage source of the control circuit is one set of DC high-voltage power supply. The insulation degradation comparison test under steady-state pure DC voltage is conducted on the test bushing using the DC high-voltage power supply.

[0033] In step S1, the effective values ​​of the steady-state voltage component, the effective values ​​of the high-frequency voltage component, the frequency and peak value of the high-frequency voltage component, and the ratio of the effective values ​​of the steady-state voltage component to the effective values ​​of the high-frequency voltage component in the composite voltage are determined based on the measured waveform, the simulated waveform, or research requirements. Specifically, the ratio of the effective values ​​of the steady-state voltage component to the effective values ​​of the high-frequency voltage component in the composite voltage can be calculated based on the effective values ​​of the steady-state voltage component and the effective values ​​of the high-frequency voltage component, or it can be set according to actual research requirements. This embodiment does not impose any restrictions on this.

[0034] For measured or simulated waveforms, the steady-state voltage RMS value, high-frequency voltage RMS value, high-frequency voltage frequency, and peak value are calculated based on the waveform. Specifically, FFT decomposition is performed on the waveform to obtain the peak values ​​of voltages at different frequencies, and the RMS value of the component voltages is calculated based on the peak values. Furthermore, the ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage can be calculated based on the steady-state voltage RMS value and the high-frequency voltage RMS value, or the ratio can be set according to research requirements.

[0035] Preferably, the steady-state voltage RMS value, high-frequency voltage RMS value, high-frequency voltage frequency, and peak value are calculated using the Fourier decomposition method.

[0036] Composite voltage equivalent RMS value U total It can be obtained from the formula. As a control group, a steady-state pure DC voltage or pure power frequency voltage is applied to the test bushing of the same design and model. The equivalent effective value of the steady-state voltage and the equivalent effective value of the composite voltage in the control group are then compared. U total equal.

[0037] When the steady-state voltage is the power frequency voltage, according to the formula Calculate the equivalent effective value of the composite voltage U total In the formula, U ac ＇ This represents the effective value of the power frequency component voltage in the composite voltage. U h This represents the peak value of the high-frequency component of the composite voltage.

[0038] When the steady-state voltage is a DC voltage, according to the formula Calculate the equivalent effective value of the composite voltage U total In the formula, U dc ＇ This represents the effective value of the DC component voltage in the composite voltage. U h This represents the peak value of the high-frequency component of the composite voltage.

[0039] The equivalent effective value of the composite voltage can be calculated using the above formula. U totalThis allows us to determine the equivalent effective value of the steady-state voltage, thus achieving a match between the equivalent effective value of the composite voltage and the effective value of the steady-state voltage under composite operating conditions. The test under composite voltage and the control test under steady-state voltage are started and run synchronously, ensuring that the test environment, test duration, total voltage energy input, and sampling frequency of the insulation parameters of the test specimen are consistent, thereby ensuring the scientific validity and effectiveness of the comparative test data.

[0040] In control step S2, the two pre-selected sample sleeves are installed into the test circuit and the control circuit respectively. The voltage value of the voltage source in the test circuit is controlled to be increased to the equivalent effective value of the composite voltage, and the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage is kept constant. The voltage value of the voltage source in the control circuit is simultaneously controlled to be increased to the equivalent effective value of the steady-state voltage.

[0041] Specifically, the two sample sleeves selected in step S5 are installed into the test circuit and the control circuit respectively. Based on the ratio of the steady-state component voltage RMS value to the high-frequency component voltage RMS value in the composite voltage, the frequency of the high-frequency component voltage, and the equivalent RMS value of the composite voltage... U total The voltage values ​​of the voltage sources in the test and control circuits are synchronously increased to the equivalent effective value of the steady-state voltage. U total Preferably, the voltage output values ​​of the voltage source in the test circuit and the voltage source output values ​​in the control circuit are controlled by a closed-loop regulation algorithm to gradually increase to... U total During the enhancement process, the ratio of the effective value of the steady-state voltage component to the effective value of the high-frequency voltage component in the composite voltage should be kept constant.

[0042] More specifically, the control system sets the frequency of the high-frequency component voltage, the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, and the equivalent effective value of the composite voltage. U total The control system synchronously controls the voltage increase of the voltage source in the test circuit and the control circuit.

[0043] During the boosting process, the boosting rate of the voltage sources in the test and control circuits is dynamically controlled based on the acquired waveforms of the composite voltage and steady-state voltage. Specifically, during the boosting process, the waveforms of the composite voltage and steady-state voltage are acquired in real time. The true effective value of the composite voltage is calculated based on the waveform of the composite voltage, and the true effective value of the steady-state voltage is calculated based on the waveform of the steady-state voltage. Then, the boosting rate of each voltage source is dynamically fine-tuned through a closed-loop voltage regulation algorithm to offset the effective value deviation caused by the high-frequency voltage in real time. This ensures that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage remains constant, and that the equivalent effective value of the composite voltage is equal to the equivalent effective value of the steady-state voltage.

[0044] In practice, the composite voltage waveform is acquired by the composite voltage measurement module, and the steady-state voltage waveform is acquired by the steady-state voltage measurement module.

[0045] In test step S3, insulation degradation comparison test was carried out simultaneously on the two test bushings, and insulation performance parameters of the two test bushings were collected.

[0046] Specifically, a long-term insulation degradation comparison test was conducted by continuously applying a composite power supply and a steady-state voltage to two test bushings. During the test, key insulation performance parameters such as capacitance, dielectric loss tangent, partial discharge, insulation resistance, and leakage current of the test bushings were measured in real time and synchronously. Furthermore, data sampling, storage, and preprocessing were completed every 3 minutes.

[0047] In step S4, based on the insulation performance parameters of the two test bushings, the differences in insulation degradation under steady-state voltage and composite voltage are analyzed.

[0048] Specifically, based on the insulation performance parameters of the two test bushings, the rate of change, degradation initiation time, and degree of degradation of the insulation parameters of the test bushings under pure DC or pure power frequency and superimposed high frequency composite voltage are compared laterally to quantify the accelerating effect of high frequency voltage superposition on bushing insulation degradation.

[0049] When the parameters of any test bushing reach the failure threshold, stop the voltage output of the corresponding circuit, record the failure data and difference characteristics simultaneously, plot the change curve of insulation parameters with test duration, analyze the deterioration acceleration mechanism of high-voltage bushing insulation caused by high-frequency disturbance voltage, and write a test analysis report.

[0050] As can be seen, in this embodiment, the test conditions are first determined, and the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, as well as the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage, are determined. Then, the voltage sources in the test circuit and the control circuit are controlled to be raised to the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage, respectively. Simultaneously, insulation degradation comparison tests are conducted on the two test bushings, and the insulation performance parameters of the two test bushings are collected. Then, the difference in insulation degradation under steady-state voltage and composite voltage is analyzed. In this way, the composite electric field environment of power frequency / DC steady-state voltage superimposed with high-frequency harmonic voltage can be realistically simulated. Furthermore, the two test bushings are installed in the test circuit and the control circuit, respectively, and the two test bushings are compared synchronously, which allows for a direct comparison. By comparing the degradation differences between pure power frequency / DC steady-state voltage and high-frequency superimposed composite voltage, this study ensures that the equivalent effective value of the increased steady-state voltage is equal to the equivalent effective value of the composite voltage when increasing the voltage source of the test circuit and the control circuit. It also ensures that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage remains constant. This guarantees coordinated control during the voltage boosting process, thus ensuring the authenticity, comparability, and accuracy of the test. This allows for accurate analysis of the insulation degradation differences under steady-state voltage and composite voltage, providing reliable experimental support for high-voltage bushing insulation performance evaluation, research on differentiated degradation mechanisms under high-frequency disturbances, and service life prediction. It solves the problem that existing technologies cannot accurately determine the differences in bushing insulation degradation patterns under DC / power frequency voltage superimposed with high-frequency voltage.

[0051] This embodiment sets up two dedicated test conditions: power frequency superimposed with high frequency and DC superimposed with high frequency. Based on field measurements and Fourier waveform decomposition technology, it reconstructs the composite electric field environment of the bushing's power frequency / DC steady-state voltage plus high-frequency disturbance voltage. Simultaneously, by controlling the ratio of the effective values ​​of the steady-state and high-frequency components in the constant composite voltage, it simulates the voltage waveform characteristics of the bushing during actual operation. This solves the problems of simulation distortion and large deviations between the aging mechanism and the actual field conditions in traditional single-voltage test conditions, significantly improving the engineering reference value of the test results and providing a reliable test basis for the analysis of the actual insulation failure mechanism of the bushing.

[0052] This embodiment employs a synchronous parallel testing scheme with two test samples from the same batch and using the same parameters. The test environment, runtime, total voltage energy input, and data sampling frequency for the two test bushings are strictly standardized, with only high-frequency voltage disturbances retained as the sole test variable. Through synchronous comparative testing under a superimposed composite voltage condition of power frequency / DC steady-state voltage and high-frequency voltage, the differences in insulation degradation under steady-state voltage and composite voltage are analyzed. This effectively avoids individual differences in the test bushings and system test errors, improving the credibility and scientific rigor of the test comparison conclusions.

[0053] This embodiment employs a dual PID closed-loop control technology that combines a constant ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage with the equivalent voltage RMS value. During the experiment, the voltage amplitude is dynamically fine-tuned to offset the RMS value increment caused by the high-frequency voltage superposition in real time. Under the premise of ensuring a constant ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage, the equivalent voltage RMS values ​​of the composite and steady-state operating conditions are completely equivalent. The voltage matching deviation is controlled within ±0.3% throughout the entire process. This solves the defects of inconsistent energy input, non-unique experimental variables, and distorted comparison data in traditional superposition experiments, and ensures the accuracy and effectiveness of the control experiment data from the perspective of control principle.

[0054] The process of high-voltage bushing insulation degradation test with superimposed high-frequency voltage is described in conjunction with specific embodiments: Construct a dual-sample synchronous control test platform.

[0055] Test samples: Two epoxy-impregnated paper bridge arm through-wall reduction bushings of the same batch and specification for flexible direct current systems were selected; both samples were made of epoxy-impregnated paper, with a structure of an epoxy-impregnated paper bushing capacitor core plus a composite outer jacket, an initial capacitance of 555.7pF, a dielectric loss factor of 0.3% for both, a partial discharge of less than 5pC for both, and a main insulation resistance greater than 50GΩ for both. Test environment: constant temperature 25℃, humidity less than 70%RH, dual-station tests were conducted in the same environment to maintain complete consistency.

[0056] Test Condition: Condition 1 (Comparative Test of Insulation Deterioration between Power Frequency and High-Frequency Voltage Superimposed on Power Frequency Voltage) was selected. Based on the measured waveform characteristics of the through-wall bushing voltage of the bridge arm, the test parameters were determined according to the principle of electric field equivalence after Fourier decomposition: the effective value of the power frequency component voltage was 100kV, the frequency of the superimposed high-frequency component voltage was 10kHz, and the peak value was 28.28kV. The ratio of the effective values ​​of the power frequency and high-frequency component voltages was set to a constant 5:1 (100kV:20kV). The unified total equivalent effective value was calculated. U total =101.98kV, the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage are the same, that is, both are 101.98kV. The control system automatically calibrates the parameters to ensure that the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage are equal, and that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage is constant.

[0057] 1. Sample Fixing and Pretreatment: Fix the two sample sleeves to the test support frame respectively, complete the high voltage and grounding wiring, and simultaneously install and calibrate the capacitance, dielectric loss, partial discharge and leakage current sensors to ensure that the detection accuracy of the two stations is completely consistent. Remove the stains and moisture from the surface of the sample sleeves to complete the pretreatment before the test.

[0058] 2. Parameter configuration and operating condition selection: Select the insulation degradation comparison test of power frequency superimposed high frequency voltage and power frequency voltage through the human-machine interface of the control system. Enter the equivalent effective value of composite voltage of 101.98kV and the frequency of superimposed high frequency component voltage of 10kHz. The ratio of the effective value of steady-state component voltage to the effective value of high frequency component voltage in composite voltage is kept constant at 5:1.

[0059] 3. Dual-channel synchronous voltage boost and closed-loop control: Upon equipment startup, two sets of industrial frequency high-voltage power supplies and one set of high-frequency high-voltage power supplies start synchronously. The control system controls each voltage source to synchronously and smoothly boost the voltage. During the boost process, the dual-channel voltage waveforms are acquired in real time and the true effective value of the voltage is calculated. The output parameters are dynamically fine-tuned to ensure, on the one hand, that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage remains constant, and on the other hand, that the equivalent effective value of the composite voltage is equal to the equivalent effective value of the steady-state voltage. When the output voltage reaches... U total After that, it remained stable. U total The voltage was 101.98kV, with no distortion or parameter offset in the waveform. After stabilizing for 5 minutes, it entered the long-term degradation test stage. The output waveform is shown below. Figure 4 .

[0060] 4. Synchronous accelerated degradation test: The two test bushings are simultaneously subjected to long-term insulation degradation control test. The system collects the capacitance, dielectric loss, partial discharge and leakage current of the two test bushings every 3 minutes, stores and preprocesses the data in real time, and dynamically monitors the changes in the insulation status of the two test bushings.

[0061] 5. Test Termination Judgment and Result Analysis: When the capacitance of the test bushing increases significantly and it can be determined that at least one layer of capacitor has broken down, the test ends, the equipment is automatically powered off, the circuit is fully discharged and grounded, the time sequence test data of the two test bushings are sorted out, the parameter change comparison curve is plotted, the high-frequency voltage degradation acceleration coefficient is quantified, the insulation degradation difference between steady-state and composite conditions is compared and analyzed, and a control test analysis report is generated.

[0062] The test results showed that the insulation degradation of the two bushing samples differed significantly. After 65 hours of insulation degradation testing, the bushing capacitance and dielectric loss factor under power frequency voltage did not change significantly. However, under a combined power frequency and high frequency voltage, the bushing capacitance increased from 555.7 pF to 934.9 pF, and the power frequency dielectric loss factor increased from 0.3% to 0.58%, indicating that the internal capacitance layer of the bushing had broken down. Typical partial discharge patterns measured before the bushing capacitance layer broke down under the combined power frequency and high frequency voltage are shown in [reference missing]. Figure 6 and Figure 7 It is evident that the dielectric loss and capacitance parameters of the test bushing change gradually under pure power frequency voltage, but long-term degradation can still lead to partial discharge. The discharge quantity and discharge phase range are greater under power frequency superimposed with high frequency voltage.

[0063] It should be noted that, Figure 5 The waveform of a DC superimposed 20kHz high-frequency voltage output is shown. This waveform is derived by superimposing a DC high-frequency voltage, with the high-frequency component voltage frequency of 20kHz as an example.

[0064] Device Example: This embodiment also proposes a control device for high-voltage bushing insulation degradation test with superimposed high-frequency voltage. This control device corresponds to the above-described high-voltage bushing insulation degradation test method with superimposed high-frequency voltage. The specific implementation process of the high-voltage bushing insulation degradation test method with superimposed high-frequency voltage is described above and will not be repeated here.

[0065] See Figure 3 The high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage includes: a control system 1, a test circuit voltage source 2, a control circuit voltage source 3, an insulation parameter measuring device 4, and an analysis system 5. The control system 1 is electrically connected to both the test circuit voltage source 2 and the control circuit voltage source 3. The control system 1 is used to pre-set the ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage, as well as the equivalent RMS value of the composite voltage and the equivalent RMS value of the steady-state voltage. Based on the ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage, the control system 1 controls the voltage value of the test circuit voltage source 2 to increase to the equivalent RMS value of the composite voltage, and simultaneously controls the voltage value of the control circuit voltage source 3 to increase to the equivalent RMS value of the steady-state voltage.

[0066] Specifically, the steady-state voltage is the power frequency voltage or DC voltage.

[0067] Determine the effective values ​​of the steady-state voltage component, the effective values ​​of the high-frequency voltage component, the frequency and peak value of the high-frequency voltage component, and the ratio of the effective values ​​of the steady-state voltage component to the effective values ​​of the high-frequency voltage component in the composite voltage based on the measured waveform, simulated waveform, or research requirements.

[0068] More specifically, the effective value of the steady-state component voltage, the effective value of the high-frequency component voltage, the frequency and peak value of the high-frequency component voltage can be directly set according to research needs. The ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage can be calculated based on the effective values ​​of the steady-state component voltage and the effective value of the high-frequency component voltage, or it can be set according to actual research needs. This embodiment does not impose any restrictions on this.

[0069] For measured or simulated waveforms, calculate the RMS values ​​of the steady-state voltage component, the RMS values ​​of the high-frequency voltage component, the frequency of the high-frequency voltage component, and the peak value. Furthermore, calculate the ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value based on the steady-state and high-frequency voltage RMS values, or set the ratio according to research requirements.

[0070] When the steady-state voltage is the power frequency voltage, according to the formula Calculate the equivalent effective value of the composite voltage U total In the formula, U ac ＇ This represents the effective value of the power frequency component voltage in the composite voltage. U h This represents the peak value of the high-frequency component of the composite voltage.

[0071] When the steady-state voltage is a DC voltage, according to the formula Calculate the equivalent effective value of the composite voltage U total In the formula, U dc ＇ This represents the effective value of the DC component voltage in the composite voltage. U h This represents the peak value of the high-frequency component of the composite voltage.

[0072] The equivalent effective value of the composite voltage can be calculated using the above formula. U total Equivalent RMS value of steady-state voltage and equivalent RMS value of composite voltage U total equal.

[0073] After determining the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, the equivalent effective value of the composite voltage, the equivalent effective value of the steady-state voltage, and the frequency of the high-frequency component voltage, these settings are configured in control system 1.

[0074] Two pre-selected bushings with identical parameters were installed in the test circuit and control circuit, respectively. The test circuit applied a steady-state voltage superimposed with a high-frequency voltage, while the control circuit applied a steady-state voltage. The test conditions were determined based on the type of bushing selected. For bushings subjected to power frequency superimposed with high-frequency voltage, a comparative insulation degradation test was conducted between power frequency superimposed with high-frequency voltage and power frequency voltage. For bushings subjected to DC superimposed with high-frequency voltage, a comparative insulation degradation test was conducted between DC superimposed with high-frequency voltage and DC voltage.

[0075] When the test sample bushing is subjected to a superimposed high-frequency voltage at the power frequency, the voltage source 3 of the control circuit is a high-voltage power supply at the power frequency; the voltage source 2 of the test circuit includes a high-frequency high-voltage power supply and a power frequency high-voltage power supply connected in parallel.

[0076] When the test sample sleeve is subjected to a DC superimposed high-frequency voltage, the control circuit voltage source 3 is a DC high-voltage power supply; the test circuit voltage source 2 includes a high-frequency high-voltage power supply and a DC high-voltage power supply connected in parallel.

[0077] The high-frequency high-voltage power supply is used to generate high-frequency, high-voltage signals, with a frequency range of 1kHz to 200kHz and an adjustable amplitude of 0 to 20kV. Methods for generating high-frequency, high-voltage signals include, but are not limited to, using multi-level cascaded power electronic transformers, or cascading low-voltage, high-frequency signals with a power amplifier before outputting them through a high-frequency transformer. The power frequency / DC high-voltage power supply is used to provide steady-state reference test voltages and also provides a steady-state voltage basis for power frequency / DC superimposed high-frequency composite voltages.

[0078] Preferably, the high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage further includes: a low-frequency voltage isolation module 8 and a high-frequency voltage isolation module 9. The low-frequency voltage isolation module 8 is installed in the test circuit and is connected in series with the high-frequency high-voltage power supply. Specifically, the low-frequency voltage isolation module 8 uses a high-frequency coupling capacitor, exhibiting low impedance at high frequencies, resulting in a very small voltage drop across it. However, it exhibits high impedance at power frequency / DC, thus blocking power frequency / DC components and protecting the high-frequency power supply from interference from the power frequency / DC high-voltage power supply. This achieves interference-free and accurate superposition of the power frequency voltage and high-frequency voltage, avoiding mutual cancellation and waveform distortion between the two voltages.

[0079] The high-frequency voltage isolation module 9 is installed in the test circuit and is connected in series with the power frequency high-voltage power supply or the DC high-voltage power supply. Specifically, the high-frequency voltage isolation module 9 uses resistors and inductors to form a high-frequency wave trap, which is directly connected to the DC / power frequency high-voltage power supply. It is used to block high-frequency components, limit high-frequency current, and reduce the high-frequency voltage that the DC / power frequency high-voltage power supply is subjected to. At the same time, it can limit the transient overcurrent of the power frequency high-voltage power supply during fault conditions, thus having the dual functions of waveform isolation and fault protection.

[0080] In practice, the high-frequency high-voltage power supply is connected in series with the low-frequency voltage isolation module 8 and then in series with the DC / power frequency high-voltage power supply with the high-frequency voltage isolation module 9 before being connected in parallel to output to the test sample bushing.

[0081] After the test circuit and the control circuit are set up, the control system 1 controls the voltage value of the voltage source 2 in the test circuit to increase to the equivalent effective value of the composite voltage, and simultaneously controls the voltage value of the voltage source 3 in the control circuit to increase to the equivalent effective value of the steady-state voltage. During the increase process, the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage is kept constant.

[0082] In practical implementation, control system 1 may include: a PLC controller, a computer, and a communication module. Control system 1 can use a closed-loop regulation algorithm to control the voltage values ​​of both the test loop voltage source 2 and the control loop voltage source 3 to be increased to [a specific value]. U total The control system 1 incorporates a PID algorithm to synchronously achieve closed-loop control that keeps the ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage constant, and ensures that the equivalent RMS value of the composite voltage is equal to the equivalent RMS value of the steady-state voltage.

[0083] The insulation parameter measuring device 4 is used to measure the insulation performance parameters of the test bushing in the test circuit and the control circuit, respectively. Specifically, the insulation parameter measuring device 4 integrates a partial discharge sensor, a leakage current sensor, a capacitance and dielectric loss factor monitoring unit, an insulation resistance tester, a temperature sensor, etc., and can simultaneously and in real time collect multi-dimensional insulation parameters such as partial discharge, capacitance, dielectric loss, leakage current, surface temperature, and insulation resistance of the two test bushings, realizing comprehensive monitoring of the deterioration state.

[0084] Analysis system 5 is electrically connected to insulation parameter measuring device 4. Analysis system 5 is used to analyze the differences in insulation degradation under regulated voltage and combined voltage based on the insulation performance parameters of the test bushings in the test and control circuits. Specifically, analysis system 5 is connected to each sensor and instrument in insulation parameter measuring device 4, independently stores the test parameters of the two test bushings, and performs functions such as data storage, preprocessing, curve plotting, and insulation degradation state determination. Analysis system 5 has a built-in multi-voltage type insulation degradation comparison analysis algorithm, comparing the differences in insulation parameters and degradation rates under pure DC, pure power frequency, and superimposed high-frequency combined operating conditions, automatically generating comparison analysis reports and difference curves, and identifying differentiated degradation characteristics caused by high-frequency voltage.

[0085] Preferably, the high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage further includes: a composite voltage measurement module 6 and a steady-state voltage measurement module 7. The composite voltage measurement module 6 is used to measure the composite voltage waveform experienced by the test bushing in the test circuit. Specifically, the composite voltage measurement module 6 can be a resistive-capacitive voltage divider.

[0086] The steady-state voltage measurement module 7 is used to measure the steady-state voltage waveform experienced by the test bushing in the control circuit. Specifically, the steady-state voltage measurement module 7 can be a resistive-capacitive voltage divider or a resistive voltage divider.

[0087] Control system 1 is electrically connected to both composite voltage measurement module 6 and steady-state voltage measurement module 7. Control system 1 dynamically adjusts the boost rate of voltage source 2 in the test circuit and voltage source 3 in the control circuit based on the composite voltage waveform and the steady-state voltage waveform. Specifically, control system 1 calculates the true effective value of each frequency component of the composite voltage based on the composite voltage waveform, and calculates the true effective value of each frequency component of the steady-state voltage waveform based on the steady-state voltage waveform. Control system 1 uses a PID control algorithm to output adjustment commands to the corresponding voltage sources based on the deviation value and compensation amount, dynamically fine-tuning the boost rate of each voltage source and continuously correcting the voltage amplitude. This ensures that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage remains constant, while also ensuring that the equivalent effective value of the composite voltage is equal to the equivalent effective value of the steady-state voltage.

[0088] In practice, the insulation parameter measuring device 4 is also electrically connected to the composite voltage measuring module 6 and the steady-state voltage measuring module 7.

[0089] In this embodiment, the test circuit and the control circuit are independent of each other and electromagnetically isolated, and can synchronously output steady-state voltage and composite voltage. The control system 1 supports precise voltage ratio control and equal effective value closed-loop compensation. The voltage parameter deviation throughout the process is ≤±0.3%, and the insulation parameter sampling period is 3 minutes, which meets the requirements of long-term synchronous control aging test.

[0090] Since the high-voltage bushing insulation degradation test method with superimposed high-frequency voltage has the above-mentioned effects, the high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage corresponding to the test method also has the corresponding technical effects.

[0091] This embodiment includes a low-frequency voltage isolation module and a high-frequency voltage isolation module. The low-frequency voltage isolation module blocks steady-state high-voltage backflow, while the high-frequency voltage isolation module blocks high-frequency disturbances and crosstalk. This achieves interference-free and precise superposition of high and low frequency voltages, eliminating problems such as waveform distortion, voltage cancellation, and power supply damage. It effectively ensures stable voltage parameters and pure waveforms during long-term insulation degradation tests, while providing effective electrical protection for both high and low voltage power supplies. This improves the operational safety, anti-interference capability, and service life of the entire test device, meeting the requirements for high-precision, long-term accelerated insulation aging tests.

[0092] This embodiment simultaneously collects multi-dimensional insulation performance parameters of two test bushings, enabling it to fully capture the subtle temporal changes throughout the entire bushing insulation degradation process. Through a built-in differential comparison algorithm, it compares the differences in insulation parameter change rates, degradation initiation times, and aging accumulation under different operating conditions, quantifies the high-frequency voltage insulation degradation acceleration coefficient, and traces the mechanism by which high-frequency disturbances induce premature bushing insulation failure.

[0093] It should be noted that the principle of the high-voltage bushing insulation degradation test method and control device with superimposed high-frequency voltage in this invention is the same, and the relevant parts can be referred to each other.

[0094] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0095] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0096] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for testing the insulation degradation of high-voltage bushings by superimposed high-frequency voltage, characterized in that, Includes the following steps: The steps are determined, the test conditions are determined, and the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, as well as the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage are determined; wherein, the equivalent effective value of the composite voltage is equal to the equivalent effective value of the steady-state voltage, the steady-state voltage is the power frequency voltage or DC voltage, and the composite voltage is the voltage obtained by superimposing the high-frequency voltage on the steady-state voltage; The control steps involve installing two pre-selected sample sleeves into the test circuit and the control circuit, respectively, controlling the voltage value of the voltage source in the test circuit to increase to the equivalent effective value of the composite voltage, and ensuring that the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage remains constant, while simultaneously controlling the voltage value of the voltage source in the control circuit to increase to the equivalent effective value of the steady-state voltage. The test procedure involves simultaneously conducting a comparative insulation degradation test on the two test bushings and collecting the insulation performance parameters of the two test bushings. The analysis steps involve analyzing the difference in insulation degradation under the steady-state voltage and the composite voltage based on the insulation performance parameters of the two test bushings.

2. The high-voltage bushing insulation degradation test method based on superimposed high-frequency voltage according to claim 1, characterized in that, In the determination step The effective values ​​of the steady-state component voltage, the effective values ​​of the high-frequency component voltage, the frequency and peak value of the high-frequency component voltage, and the ratio of the effective values ​​of the steady-state component voltage to the effective values ​​of the high-frequency component voltage in the composite voltage are determined based on the measured waveform, the simulated waveform, or research requirements.

3. The high-voltage bushing insulation degradation test method based on superimposed high-frequency voltage according to claim 2, characterized in that, For measured or simulated waveforms, calculate the steady-state voltage RMS value, high-frequency voltage RMS value, high-frequency voltage frequency, and peak value based on the waveform. Then, calculate the ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage based on the steady-state voltage RMS value and the high-frequency voltage RMS value, or set the ratio of the steady-state voltage RMS value to the high-frequency voltage RMS value in the composite voltage according to research needs.

4. The high-voltage bushing insulation degradation test method based on superimposed high-frequency voltage according to claim 2 or 3, characterized in that, When the steady-state voltage is the power frequency voltage, according to the formula Calculate the equivalent effective value of the composite voltage U total In the formula, U ac ＇ This represents the effective value of the power frequency component voltage in the composite voltage. U h The peak value of the high-frequency component of the composite voltage; When the steady-state voltage is a DC voltage, according to the formula Calculate the equivalent effective value of the composite voltage U total In the formula, U dc ＇ This represents the effective value of the DC component voltage in the composite voltage. U h This represents the peak value of the high-frequency component of the composite voltage.

5. The high-voltage bushing insulation degradation test method based on superimposed high-frequency voltage according to claim 2, characterized in that, In the control steps The voltage values ​​of the voltage sources in the test circuit and the control circuit are synchronously controlled according to the ratio of the steady-state component voltage RMS value to the high-frequency component voltage RMS value in the composite voltage, the frequency of the high-frequency component voltage, the equivalent RMS value of the composite voltage, and the equivalent RMS value of the steady-state voltage. During the boosting process, the boosting rate of the voltage sources in the test circuit and the control circuit is dynamically controlled based on the waveforms of the collected composite voltage and steady-state voltage.

6. The high-voltage bushing insulation degradation test method based on superimposed high-frequency voltage according to claim 1, characterized in that, Before the determination step, the method further includes: selecting two sample sleeves with the same parameters and pre-treating the two sample sleeves; In the determination step, the test conditions are determined according to the type of the selected test sample sleeve, and the voltage sources of the test circuit and the control circuit are determined according to the test conditions. The test conditions include: a comparative test of insulation degradation between power frequency superimposed high frequency voltage and power frequency voltage, and a comparative test of insulation degradation between DC superimposed high frequency voltage and DC voltage. For the insulation degradation comparison test between power frequency superimposed high frequency voltage and power frequency voltage, the voltage source of the test circuit includes: power frequency high voltage power supply and high frequency high voltage power supply, and the voltage source of the control circuit is power frequency high voltage power supply; For the insulation degradation comparison test between DC superimposed high-frequency voltage and DC voltage, the voltage source of the test circuit includes: DC high-voltage power supply and high-frequency high-voltage power supply, and the voltage source of the control circuit is DC high-voltage power supply.

7. The high-voltage bushing insulation degradation test method based on superimposed high-frequency voltage according to claim 1, characterized in that, In the analysis steps described When the parameters of any test bushing reach the failure threshold, stop the voltage output of the corresponding circuit, plot the curve of insulation parameters changing with the test duration, and analyze the mechanism of accelerated insulation degradation.

8. A control device for high-voltage bushing insulation degradation test using the high-voltage bushing insulation degradation test method with superimposed high-frequency voltage as described in any one of claims 1 to 7, characterized in that, include: The system comprises a control system (1), a test circuit voltage source (2), a control circuit voltage source (3), an insulation parameter measuring device (4), and an analysis system (5); among which, The control system (1) is electrically connected to both the test circuit voltage source (2) and the control circuit voltage source (3). It is used to pre-set the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, as well as the equivalent effective value of the composite voltage and the equivalent effective value of the steady-state voltage. Based on the ratio of the effective value of the steady-state component voltage to the effective value of the high-frequency component voltage in the composite voltage, the control system controls the voltage value of the test circuit voltage source (2) to be increased to the equivalent effective value of the composite voltage, and simultaneously controls the voltage value of the control circuit voltage source (3) to be increased to the equivalent effective value of the steady-state voltage. The insulation parameter measuring device (4) is used to measure the insulation performance parameters of the test bushing in the test circuit and the control circuit respectively; The analysis system (5) is electrically connected to the insulation parameter measuring device (4) and is used to analyze the difference in insulation degradation under regulated voltage and composite voltage based on the insulation performance parameters of the test bushing in the test circuit and the control circuit.

9. The high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage according to claim 8, characterized in that, Also includes: Composite voltage measurement module (6) and steady-state voltage measurement module (7); wherein, The composite voltage measurement module (6) is used to measure the composite voltage waveform borne by the test bushing in the test circuit; The steady-state voltage measurement module (7) is used to measure the steady-state voltage waveform of the test bushing in the control circuit; The control system (1) is electrically connected to the composite voltage measurement module (6) and the steady-state voltage measurement module (7), and is used to dynamically adjust the boost rate of the test circuit voltage source (2) and the control circuit voltage source (3) according to the composite voltage waveform and the steady-state voltage waveform.

10. The high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage according to claim 8, characterized in that, When the test sample sleeve is subjected to a superimposed high-frequency voltage at the power frequency, the voltage source (3) of the control circuit is a high-voltage power supply at the power frequency; the voltage source (2) of the test circuit includes: a high-frequency high-voltage power supply and a high-voltage power supply at the power frequency connected in parallel; When the test sample sleeve is subjected to a DC superimposed high-frequency voltage, the control circuit voltage source (3) is a DC high-voltage power supply; the test circuit voltage source (2) includes: a high-frequency high-voltage power supply and a DC high-voltage power supply connected in parallel; The high-voltage bushing insulation degradation test control device with superimposed high-frequency voltage further includes: a low-frequency voltage isolation module (8) and a high-frequency voltage isolation module (9); wherein, The low-frequency voltage isolation module (8) is installed in the test circuit and connected in series with the high-frequency high-voltage power supply; The high-frequency voltage isolation module (9) is installed in the test circuit and connected in series with the power frequency high voltage power supply or the DC high voltage power supply.

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