A method and system for evaluating the state of discharge of a high-voltage cable buffer layer moisture defect

Abstract

The application discloses a kind of high-voltage cable buffer layer damp defect discharge state evaluation method and system, belong to high-voltage cable partial discharge detection technical field.The high-voltage cable buffer layer damp defect discharge state evaluation method provided by the application, test parameters are preset by adjustable square wave voltage generator, in output voltage regulation stage, gradually increase output voltage intensity with first preset step size;When output voltage reaches first preset peak value and still does not trigger partial discharge, change to the rising edge slope of polarity reversal stage, improve the rising edge slope of polarity reversal stage by second preset step size, enhance the rising edge slope of square wave voltage polarity conversion stage to stimulate latent partial discharge defect;Not only can reduce the volume requirement of on-site power supply capacity and test device, and will not cause damage to high-voltage cable, while effectively stimulating buffer layer composite material damp defect discharge.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage cable partial discharge detection, and in particular to a state evaluation method and system for high-voltage cable buffer layer moisture defect discharge. BACKGROUND

[0002] In the power system, high-voltage cables are the core components in long-distance power transmission and urban power grid backbone network construction, and their safe and stable operation is directly related to the operation reliability and power supply continuity of the power grid system. The buffer layer of the high-voltage cable usually uses composite materials to buffer mechanical stress and absorb moisture invading the inside of the cable to prevent damage to the main insulation of the high-voltage cable.

[0003] Due to the influence of moisture invasion and electrochemical corrosion during long-term service, the composite material of the buffer layer is prone to moisture problems, which leads to poor contact with the main insulation of the high-voltage cable, and then causes partial discharge phenomena such as suspended discharge, and even thermal ablation, eventually developing into a breakdown fault. Therefore, developing a state evaluation of the moisture defect discharge of the high-voltage cable buffer layer has become a necessary means to ensure the reliability of the power system.

[0004] In the prior art, the discharge of the high-voltage cable buffer layer is usually achieved by excitation, and the existing excitation methods include power frequency voltage, direct current oscillation wave and alternating current oscillation wave. Among them, although the power frequency voltage has good consistency with the operating conditions, it requires high power capacity and large test device volume, which is not convenient for on-site testing, and the high-voltage cable as a large-capacitance load takes a long time to charge. The direct current oscillation wave can cause damage to the high-voltage cable during the charging process. The alternating current oscillation wave has good equivalence to the power frequency voltage, low power capacity requirement and relatively portable test device, and is widely used in partial discharge detection of high-voltage cables, but has the problems of fast voltage waveform attenuation and insufficient excitation ability for moisture defect discharge of the buffer layer. SUMMARY

[0005] The purpose of the present application is to provide a state evaluation method and system for moisture defect discharge of the high-voltage cable buffer layer to overcome the problem of insufficient excitation ability due to fast voltage waveform attenuation of the alternating current oscillation wave in the prior art.

[0006] The present application solves the above technical problems by the following technical solutions:

[0007] The present application provides a state evaluation method for moisture defect discharge of the high-voltage cable buffer layer, comprising the following steps:

[0008] Step one, preset test parameters on the adjustable square wave voltage generator, the test parameters include: the initial value of the output voltage, the initial value of the rising slope of the polarity reversal stage, the first preset step, the second preset step, the first preset peak value, the second preset peak value and the length and insulation state of the measured high voltage cable;

[0009] Step two, excite the measured high voltage cable, during the excitation process, according to the first preset step, the current output voltage is raised; the real-time judgment of whether the measured high voltage cable exists partial discharge during the excitation process, if the judgment result is yes, the measured high voltage cable exists partial discharge risk caused by the buffer layer moisture defect under the current test parameters, complete state evaluation; if the judgment result is no, execute step three;

[0010] Step three, judge whether the current output voltage reaches the first preset peak value, if the judgment result is yes, execute step four, if the judgment result is no, return to step two;

[0011] Step four, excite the measured high voltage cable, during the excitation process, the rising slope of the polarity reversal stage is improved according to the second preset step; real-time judgment of whether the measured high voltage cable exists partial discharge during the excitation process, if the judgment result is yes, the measured high voltage cable exists partial discharge risk caused by the buffer layer moisture defect under the current test parameters, complete state evaluation; if the judgment result is no, execute step five;

[0012] Step five, judge whether the current rising slope of the polarity reversal stage reaches the second preset peak value, if the judgment result is yes, the measured high voltage cable does not exist partial discharge risk caused by the buffer layer moisture defect under the current test parameters, complete state evaluation; if the judgment result is no, return to step four.

[0013] The further improvement of the application is that when the measured high voltage cable exists partial discharge risk caused by the buffer layer moisture defect under the current test parameters, complete state evaluation, the following steps are further included:

[0014] Signal calibration is carried out through the adjustable square wave voltage generator, and the current test parameters are output;

[0015] When the measured high voltage cable does not exist partial discharge risk caused by the buffer layer moisture defect under the current test parameters, complete state evaluation, the following steps are further included:

[0016] Signal calibration is carried out through the adjustable square wave voltage generator, and the current test parameters are output.

[0017] The further improvement of the application is that the initial value of the output voltage is 0.3 Un; Un is the rated voltage of the measured high voltage cable.

[0018] The further improvement of the present application is that the first preset step length ranges from 0.1 to 0.3 Un, wherein Un is the rated voltage of the high-voltage cable to be measured.

[0019] The further improvement of the present application is that the second preset step length ranges from 0.1 to 0.3 Un, wherein Un is the rated voltage of the high-voltage cable to be measured. , wherein, is the maximum output voltage of the adjustable square wave voltage generator.

[0020] The further improvement of the present application is that the first preset peak value ranges from 1.1 Un to 1.6 Un, wherein Un is the rated voltage of the high-voltage cable to be measured.

[0021] The further improvement of the present application is that the second preset peak value ranges from 1.1 Un to 1.6 Un, wherein Un is the rated voltage of the high-voltage cable to be measured. , wherein, is the maximum output voltage of the adjustable square wave voltage generator.

[0022] The present application also provides a state evaluation system for discharge of a damp defect of a buffer layer of a high-voltage cable, which is used to realize the state evaluation method for discharge of a damp defect of a buffer layer of a high-voltage cable as described above, and comprises a high-voltage cable to be measured, an adjustable square wave voltage generator, a partial discharge detector, a partial discharge divider, and an operation host.

[0023] The further improvement of the present application is that the output end of the adjustable square wave voltage generator is connected to the conductor core of the high-voltage cable to be measured through a high-voltage reactor.

[0024] The further improvement of the present application is that a self-checking button is arranged on the adjustable square wave voltage generator, which is used to realize the self-checking operation of the state evaluation system for discharge of a damp defect of a buffer layer of a high-voltage cable.

[0025] Compared with the prior art, the positive progress effect of the present application is that:

[0026] The application provides a state evaluation method for moisture defect discharge of a high-voltage cable buffer layer, wherein a test parameter is preset through an adjustable square wave voltage generator, and in the output voltage adjustment stage, the output voltage intensity is gradually increased by a first preset step; when the output voltage reaches a first preset peak value and still does not trigger local discharge, the rising edge slope of the polarity reversal stage is converted to the adjustment polarity, the rising edge slope of the polarity reversal stage is improved by a second preset step, and the rising edge slope of the square wave voltage polarity conversion stage is enhanced to stimulate potential local discharge defects; the method can not only reduce the volume requirements of the field power capacity and the test device, but also will not damage the high-voltage cable, and can effectively stimulate the moisture defect discharge of the buffer layer composite material. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of this application, illustrate embodiments of the application and serve to explain the principles of the application, and do not constitute improper limitations on the application.

[0028] Figure 1 It is a flowchart of the state evaluation method for moisture defect discharge of a high-voltage cable buffer layer of the application.

[0029] Figure 2 It is an output voltage waveform schematic diagram of the adjustable square wave voltage generator in a specific embodiment of the application.

[0030] Figure 3 It is a schematic diagram of the dynamic migration process of space charges at potential defects of the measured high-voltage cable under the action of the output voltage of the adjustable square wave voltage generator.

[0031] Figure 4 It is a structural schematic diagram of the state evaluation system for moisture defect discharge of a high-voltage cable buffer layer of the application.

[0032] Among them, 1, adjustable square wave voltage generator; 2, no partial discharge voltage divider; 3, partial discharge detector; 4, measured high-voltage cable; 5, high-voltage reactor. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0034] In the description of the present application, it should be understood that the terms "include" and "contain" indicate the presence of described features, whole, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0035] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and the appended claims of the present application, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0036] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present application to describe the preset ranges, etc., these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from each other. For example, the first preset range can also be referred to as the second preset range, and similarly, the second preset range can also be referred to as the first preset range without departing from the scope of the embodiments of the present application.

[0037] Depending on the context, the word "if" as used herein can be interpreted to mean "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (a stated condition or event)" can be interpreted to mean "when determined" or "in response to determining" or "when detecting (a stated condition or event)" or "in response to detecting (a stated condition or event)".

[0038] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments, which are an explanation of the present application rather than a limitation.

[0039] Referring to Figure 1 The present application provides a state evaluation method for moisture defect discharge of a high-voltage cable buffer layer, comprising the following steps:

[0040] Step one, preset test parameters on the adjustable square wave voltage generator 1, the test parameters include: the initial value of the output voltage, the initial value of the rising slope of the polarity reversal stage, the first preset step, the second preset step, the first preset peak value, the second preset peak value and the length and insulation state of the measured high-voltage cable 4;

[0041] Step two, excite the measured high-voltage cable 4, during the excitation process, according to the first preset step, increase the current output voltage; Real-time judge whether there is partial discharge in the measured high-voltage cable 4 during the excitation process, if the judgment result is yes, the measured high-voltage cable 4 has the risk of partial discharge caused by buffer layer moisture defect under the current test parameters, complete the state evaluation; If the judgment result is no, execute step three;

[0042] Step three, judge whether the current output end voltage reaches the first preset peak value, if the judgment result is yes, execute step four, if the judgment result is no, return to step two;

[0043] Step four, excite the measured high-voltage cable 4, during the excitation process, the rising edge slope of the polarity reversal stage is increased according to the second preset step size; judge whether there is partial discharge in the measured high-voltage cable 4 during the excitation process in real time, if the judgment result is yes, the measured high-voltage cable 4 has the risk of partial discharge caused by the buffer layer moisture defect under the current test parameters, and the state evaluation is completed; if the judgment result is no, execute step five;

[0044] Step five, judge whether the rising edge slope of the current polarity reversal stage reaches the second preset peak value, if the judgment result is yes, the measured high-voltage cable 4 does not have the risk of partial discharge caused by the buffer layer moisture defect under the current test parameters, and the state evaluation is completed; if the judgment result is no, return to step four.

[0045] The state evaluation of the high-voltage cable buffer layer moisture defect is realized by adjusting the output end voltage and the rising edge slope of the polarity reversal stage in stages. First, the test parameters are preset by the adjustable square wave voltage generator 1, and the test reference matching the working condition of the measured high-voltage cable 4 is established; in the output end voltage adjustment stage, the gradual voltage increasing strategy is adopted, and the output end voltage intensity is gradually increased by the first preset step size, which not only avoids the damage to the high-voltage cable caused by instantaneous high-voltage impact, but also quickly locks the critical discharge point through real-time partial discharge detection; when the output end voltage reaches the first preset peak value and still does not trigger the partial discharge, the rising edge slope of the polarity reversal stage is adjusted, the rising edge slope of the polarity reversal stage is increased by the second preset step size, and the rising edge slope of the square wave voltage polarity conversion stage is enhanced to excite the potential partial discharge defect. This dual-parameter adjustment mechanism combined with real-time feedback judgment not only overcomes the limitations of traditional single-parameter adjustment, but also ensures the safety of the test process through stage threshold control, and finally realizes the reliable evaluation of the high-voltage cable buffer layer moisture defect discharge through the dual test of the output end voltage and the rising edge slope of the polarity reversal stage.

[0046] The output voltage waveform of the adjustable square wave voltage generator 1 is a square wave voltage, which includes a direct current holding stage and a polarity reversal stage, wherein the time occupied by the direct current holding stage in each period is the duty cycle. Referring to Figure 2It can be seen that the square wave voltage is divided into two stages in a cycle: DC holding stage and polarity reversal stage. In the polarity reversal stage, the square wave voltage will cause the typical charge relaxation phenomenon of the buffer layer composite material due to its instantaneous frequency mutation characteristics, thereby reducing the starting voltage of partial discharge. Therefore, the square wave voltage can effectively stimulate the partial discharge of the buffer layer moisture defect. The polarization and conductive effect of the buffer layer composite material under different frequencies in the moisture condition are significantly different, resulting in typical frequency variation characteristics and charge accumulation effect of the dielectric parameters. The frequency variation characteristics make the space charge accumulated in the DC holding stage of the square wave voltage unable to be released instantaneously in the polarity reversal stage. The residual charge and the reversed voltage form a same polarity electric field superposition, thereby enhancing the electric field intensity at the defect, which is helpful to induce the partial discharge of the buffer layer moisture defect and improve the detection rate of the partial discharge risk caused by the buffer layer moisture defect.

[0047] Referring to Figure 3 wherein, represents the additional electric field generated by the unattenuated space charge. In the positive polarity DC stage: the high voltage cable bears positive polarity DC high voltage, the previous partial discharge activity and the space charge deposited on the surface of the buffer layer moisture defect by the DC polarization form an additional field, which weakens the background field strength. Since the voltage is constant and the superimposed field strength is lower than the starting field strength, no partial discharge occurs. In the positive polarity decline in polarity conversion: the applied square wave voltage gradually decreases from the positive polarity peak to zero, and the background field strength decreases accordingly. The positive and negative charges accumulated near the two poles of the buffer layer moisture defect migrate along the surface and neutralize each other due to the conductivity of the insulation surface, and the charges gradually attenuate. Subsequently, in the negative polarity rise in polarity conversion: the polarity of the square wave voltage is reversed and rises to the negative polarity peak. The additional electric field generated by the unattenuated space charge and the background electric field generated by the applied voltage are superimposed, which enhances the local field strength at the buffer layer moisture defect and exceeds the starting field strength, thus causing partial discharge. Finally, in the negative polarity DC stage: the polarity reversal is completed, and the square wave voltage rises to the negative polarity peak. The residual charge generated in the negative polarity rise in polarity conversion and the space charge formed by the negative polarity polarization continue to accumulate near the two poles of the buffer layer moisture defect, and it is still possible to further induce partial discharge during the rising edge of the subsequent polarity reversal stage.

[0048] Preferably, when the measured high voltage cable 4 has a buffer layer moisture defect leading to partial discharge risk under the current test parameters, the state evaluation is completed, and the following steps are further included:

[0049] Signal calibration is performed by the adjustable square wave voltage generator 1, and the current test parameters are output.

[0050] When the measured high voltage cable 4 does not have a buffer layer moisture defect leading to partial discharge risk under the current test parameters, the state evaluation is completed, and the following steps are further included:

[0051] The signal calibration is performed through the adjustable square wave voltage generator 1, and the current test parameter is output.

[0052] Through the dual mechanism of signal calibration and test parameter output, the dynamic correlation between the test result and the test condition is ensured. When there is a risk of partial discharge caused by the moisture defect of the buffer layer of the high-voltage cable, the current test parameter is output through the adjustable square wave voltage generator 1, so that the parameter causing the risk of partial discharge can be directly locked, and a quantitative basis for defect positioning is provided. When there is no risk of partial discharge caused by the moisture defect of the buffer layer, the current test parameter is also output, so that the safety threshold range under the current test parameter can be determined, the risk of partial discharge caused by the moisture defect of the buffer layer is avoided, the traceability of the state evaluation process is realized, and the evaluation benchmark of the discharge of the moisture defect of the buffer layer of the high-voltage cable is established.

[0053] Preferably, the initial value of the output terminal voltage is 0.3 Un, and the range of the first preset step size is 0.1-0.3 Un, and Un is the rated voltage of the measured high-voltage cable 4.

[0054] By limiting the initial value of the output terminal voltage and the range of the first preset step size, a parameter system considering safety and test sensitivity is constructed. The initial value of the output terminal voltage is set to 0.3 times the rated voltage of the measured high-voltage cable 4, which not only avoids the impact of the equipment caused by the too high initial output terminal voltage, but also ensures that the test starting point has sufficient excitation strength. The first preset step size is limited to 0.1 times the rated voltage of the measured high-voltage cable 4, forming a moderate voltage increment gradient, which can not only accurately capture the partial discharge critical point through step-by-step voltage increase, but also prevent the test blind area caused by too large step size. By taking Un as the benchmark, the test parameter is directly related to the electrical characteristics of the measured high-voltage cable 4, which not only ensures the standardization of the test conditions of different specifications of the measured high-voltage cable 4, but also improves the pertinence of defect detection.

[0055] Preferably, the range of the second preset step size is: , wherein, is the maximum output voltage of the adjustable square wave voltage generator 1, and the unit is V / ms.

[0056] By limiting the specific range of the second preset step, a clear quantitative basis is provided for the adjustment of the rising edge slope of the polarity reversal stage. The second preset step, as an incremental parameter in the process of increasing the rising edge slope of the polarity reversal stage, determines the degree of adjustment: if the step is too large, it may cause the rising edge slope of the polarity reversal stage to jump out of the discharge response interval of the buffer layer moisture defect, and the local discharge phenomenon cannot be accurately captured; if the step is too small, it will increase the number of invalid tests and reduce the evaluation efficiency. By scientifically setting the range of the second preset step, it is ensured that the discharge critical point of the buffer layer moisture defect can be approached with a reasonable gradient in the process of increasing the rising edge slope of the polarity reversal stage, and the test blind area or redundant operation caused by improper step selection is avoided, thereby achieving a balance between detection sensitivity and test economy.

[0057] Preferably, the range of the first preset peak value is 1.1 Un ~ 1.6 Un.

[0058] By limiting the range of the first preset peak value in the process of the output end voltage rising, a safety threshold boundary of voltage excitation is constructed. In the voltage climbing stage of step three, the first preset peak value range not only ensures that the local discharge phenomenon at the buffer layer moisture defect can be effectively excited, but also avoids damage to the main insulation of the cable caused by excessively high output end voltage. By scientific setting, a balance is achieved in the defect test within the safe tolerance range of the high-voltage cable, which improves the state evaluation efficiency and ensures the safety of the test process.

[0059] Preferably, the range of the second preset peak value is: .

[0060] By limiting the second preset peak value range of the rising edge slope of the polarity reversal stage, a clear upper limit is established in the test process, which not only ensures that the local discharge phenomenon of potential buffer layer moisture defects can be fully excited in the process of gradually increasing the rising edge slope of the polarity reversal stage, but also prevents the test equipment from being overloaded or the insulation of the high-voltage cable from being damaged due to the rising edge slope of the polarity reversal stage exceeding the tolerance of the high-voltage cable.

[0061] Based on the same inventive concept, the application also provides a high-voltage cable buffer layer moisture defect discharge state evaluation system for implementing the high-voltage cable buffer layer moisture defect discharge state evaluation method as described above, comprising a measured high-voltage cable 4, an adjustable square wave voltage generator 1, a partial discharge detector 3, a non-partial discharge voltage divider 2 and an operation host; the low-voltage end of the adjustable square wave voltage generator 1 is grounded, the output end of the adjustable square wave voltage generator 1 is connected to the conductor core of the measured high-voltage cable 4, and the shielding layer of the measured high-voltage cable 4 is grounded; the low-voltage end of the non-partial discharge voltage divider 2 is grounded, and the high-voltage end of the non-partial discharge voltage divider 2 is connected to the conductor core of the measured high-voltage cable 4; the measurement end of the non-partial discharge voltage divider 2 is connected to the partial discharge detector 3; and the operation host is electrically connected to the adjustable square wave voltage generator 1 and the partial discharge detector 3 respectively.

[0062] By constructing a cooperative system comprising the measured high-voltage cable 4, the adjustable square wave voltage generator 1, the partial discharge detector 3, the non-partial discharge voltage divider 2 and the operation host, precise state evaluation of the high-voltage cable buffer layer moisture defect discharge is realized. The output end of the adjustable square wave voltage generator 1 is connected to the conductor core of the measured high-voltage cable 4, and the low-voltage end is grounded, in combination with the shielding layer grounding design, to form a stable test loop, effectively suppressing external interference; the high-voltage end of the non-partial discharge voltage divider 2 is connected to the conductor core of the measured high-voltage cable 4, and the measurement end is connected to the partial discharge detector 3, so that the high-voltage signal is converted into a measurable signal by the non-partial discharge voltage divider 2, ensuring the accuracy of the partial discharge detection; and the operation host is electrically connected to the adjustable square wave voltage generator 1 and the partial discharge detector 3, realizing automatic adjustment of the test parameters and real-time feedback of the partial discharge signal, and improving the automation degree of the test process. By forming a closed-loop test system through specific grounding and connection methods, the safety operation demand under high-voltage environment is met, and the system's ability to capture the discharge characteristics of the buffer layer moisture defect is enhanced, solving the problems of fast attenuation of excitation waveform, heavy equipment and insufficient detection sensitivity in the traditional method.

[0063] Preferably, it further comprises a high-voltage reactor 5, and the output end of the adjustable square wave voltage generator 1 is connected to the conductor core of the measured high-voltage cable 4 through the high-voltage reactor 5.

[0064] By adding the high-voltage reactor 5 between the output end of the adjustable square wave voltage generator 1 and the conductor core of the measured high-voltage cable 4, an impedance matching network is constructed. The connection of the high-voltage reactor 5 can suppress the energy loss in the high-frequency oscillation process, delay the decay rate of the voltage waveform by adjusting the circuit resonance characteristics, maintain the waveform integrity of the excitation signal, make the square wave voltage maintain sufficient amplitude and duration during transmission, and enhance the discharge excitation ability of the buffer layer moisture defect. At the same time, the series connection of the high-voltage reactor 5 can also effectively isolate the influence of the parasitic capacitance between the generator and the cable, and improve the detection sensitivity of the partial discharge signal.

[0065] Preferably, the adjustable square wave voltage generator 1 is provided with a self-check button for realizing self-check operation of the state evaluation system of the moisture defect discharge of the buffer layer of the high-voltage cable.

[0066] By integrating the self-check button in the adjustable square wave voltage generator 1, the state evaluation system of the moisture defect discharge of the buffer layer of the high-voltage cable is provided with a self-check function. The self-check button provides an active physical interface for the operator to trigger the self-check. By executing the preset self-check program, it can be verified whether the signal output and acquisition function of the adjustable square wave voltage generator 1 and the partial discharge detector 3 are normal, which can avoid misjudgment caused by equipment failure, ensure that the equipment is in a normal working state before the test, and thus improve the reliability of the state evaluation.

[0067] In a specific embodiment of the present application, referring to Figure 4 , when the state evaluation of the moisture defect discharge of the buffer layer of the high-voltage cable is built, the operator connects the low-voltage end of the adjustable square wave voltage generator 1 to the ground, connects the output end of the adjustable square wave voltage generator 1 to the input end of the high-voltage reactor 5, connects the output end of the high-voltage reactor 5 to the conductor core of the high-voltage cable, and grounds through the high-voltage cable shielding layer, thereby completing the electrical connection of the main circuit; connects the low-voltage end of the partial discharge voltage divider 2 to the ground, and connects the high-voltage end to the conductor core of the high-voltage cable; connects the partial discharge detector 3 to the measurement end of the partial discharge voltage divider 2, thereby completing the electrical connection of the measurement unit.

[0068] By the built-in WiFi wireless communication module of the adjustable square wave voltage generator 1 and the partial discharge detector 3, the operation host and the adjustable square wave voltage generator 1 and the partial discharge detector 3 complete communication.

[0069] In a specific embodiment of the present application, the operation host can issue instructions to the adjustable square wave voltage generator 1 to complete self-checking. If the self-checking fails, the test is ended, and the safety of the test process is ensured.

[0070] Finally, it should be noted that: the above-mentioned embodiments only exist as one or more specific forms of the technical solution of the present application, and their purpose is to clearly explain the concept, principle and application mode of the present application through specific examples, and are not intended to limit the protection scope of the present application to these specific embodiments. In fact, the true value of the present application lies in its proposed technical ideas and innovative points, not its forms or implementation methods.

[0071] For those skilled in the art, after reading and understanding the technical solutions of the present application, they have the ability to make various forms of changes, modifications or equivalent replacements to the specific embodiments of the application based on their own professional knowledge and skills. These changes may include but are not limited to adjusting the value range of technical parameters, optimizing the algorithm process to improve efficiency, replacing part of the technical components to achieve better compatibility or reduce cost, etc. As long as the technical solutions after these changes still maintain the technical features required by the original invention, that is, still can realize the core function and effect of the present application, these changes should be considered as falling within the protection scope of the claims of the present application.

[0072] In addition, with the continuous progress and development of technology, new technical means and methods are emerging, which also provides a broad space for further improvement and perfection of the present application. Therefore, the protection scope of the present application should also include those reasonable foreseeable improvements and extensions based on the existing technology, as long as these improvements and extensions do not deviate from the basic principles and core ideas of the present application, they should be considered as the equivalents of the present application, and also be protected by the patent right.

Claims

1. A method for assessing the state of discharge defects caused by moisture in the buffer layer of a high-voltage cable, characterized in that, Includes the following steps: Step 1: Preset test parameters on the adjustable square wave voltage generator (1). The test parameters include: the initial value of the output voltage, the initial value of the rising edge slope during the polarity reversal stage, the first preset step size, the second preset step size, the first preset peak value, the second preset peak value, and the length and insulation status of the high voltage cable (4) under test. Step 2: Excite the high-voltage cable (4) under test. During the excitation process, increase the current output voltage according to the first preset step size. In real time, determine whether there is partial discharge in the high-voltage cable (4) under test during the excitation process. If the judgment result is yes, the high-voltage cable (4) under test has a risk of partial discharge caused by the moisture defect of the buffer layer under the current test parameters, and the status assessment is completed. If the judgment result is no, proceed to step 3. Step 3: Determine whether the current output voltage has reached the first preset peak value. If the result is yes, proceed to step 4. If the result is no, return to step 2. Step 4: Excite the high-voltage cable (4) under test. During the excitation process, increase the rising edge slope of the polarity reversal stage according to the second preset step size. In real time, determine whether there is partial discharge in the high-voltage cable (4) under test during the excitation process. If the judgment result is yes, the high-voltage cable (4) under test has a risk of partial discharge caused by the moisture defect of the buffer layer under the current test parameters, and the status assessment is completed. If the judgment result is no, proceed to step 5. Step 5: Determine whether the rising edge slope of the current polarity reversal stage has reached the second preset peak value. If the determination result is yes, the tested high voltage cable (4) does not have the risk of partial discharge caused by the moisture defect of the buffer layer under the current test parameters, and the status assessment is completed; if the determination result is no, return to step 4. The range of the first preset peak value is: 1.1 Un ~ 1.6 Un, where Un is the rated voltage of the high-voltage cable (4) under test; The range of the second preset peak value is: ,in, The maximum output voltage of the adjustable square wave voltage generator (1) is .

2. The method for assessing the state of discharge defects due to moisture in the buffer layer of a high-voltage cable according to claim 1, characterized in that, When the high-voltage cable under test (4) has a risk of partial discharge due to moisture defects in the buffer layer under the current test parameters, the condition assessment also includes the following steps: The signal is calibrated using an adjustable square wave voltage generator (1), and the current test parameters are output. When the tested high-voltage cable (4) does not have the risk of partial discharge caused by moisture defects in the buffer layer under the current test parameters, the condition assessment also includes the following steps: The signal is calibrated by an adjustable square wave voltage generator (1), and the current test parameters are output.

3. The method for assessing the state of discharge defects due to moisture in the buffer layer of a high-voltage cable according to claim 1, characterized in that, The initial value of the output voltage is 0.3 Un; Un is the rated voltage of the high-voltage cable (4) under test.

4. The method for assessing the state of discharge defects due to moisture in the buffer layer of a high-voltage cable according to claim 1, characterized in that, The first preset step size range is 0.1~0.3Un, where Un is the rated voltage of the high-voltage cable (4) under test.

5. The method for assessing the state of discharge defects due to moisture in the buffer layer of a high-voltage cable according to claim 1, characterized in that, The range of the second preset step size is: ,in, The maximum output voltage of the adjustable square wave voltage generator (1) is .

6. A condition assessment system for moisture-induced defect discharge in the buffer layer of a high-voltage cable, characterized in that, The method for assessing the state of discharge defects caused by moisture in the buffer layer of a high-voltage cable as described in any one of claims 1 to 5 includes a high-voltage cable under test (4), an adjustable square wave voltage generator (1), a partial discharge detector (3), a partial discharge divider (2), and an operating host. The low-voltage end of the adjustable square wave voltage generator (1) is grounded, and the output end of the adjustable square wave voltage generator (1) is connected to the conductor core of the high-voltage cable under test (4). The shielding layer of the high-voltage cable under test (4) is grounded. The low-voltage end of the partial discharge divider (2) is grounded, and the high-voltage end of the partial discharge divider (2) is connected to the conductor core of the high-voltage cable under test (4). The partial discharge detector (3) is connected to the measuring end of the partial discharge divider (2). The operating host is electrically connected to the adjustable square wave voltage generator (1) and the partial discharge detector (3) respectively.

7. The condition assessment system for moisture-induced defect discharge in the buffer layer of a high-voltage cable according to claim 6, characterized in that, It also includes a high-voltage reactor (5), and the output of the adjustable square wave voltage generator (1) is connected to the conductor core of the high-voltage cable (4) under test via the high-voltage reactor (5).

8. The condition assessment system for moisture-induced defect discharge in the buffer layer of a high-voltage cable according to claim 6, characterized in that, The adjustable square wave voltage generator (1) is equipped with a self-test button, which is used to realize the self-test operation of the high-voltage cable buffer layer moisture defect discharge status assessment system.

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