Cable partial discharge characteristic test method and system based on electric heating joint effect

Abstract

The invention relates to a cable partial discharge characteristic test method and system based on electric heating joint effect, and the method comprises the steps: manufacturing a cable insulation defect sample; the cable insulation defects comprise an air gap defect and a semi-conductive layer protrusion defect; applying load current to the cable insulation defect sample, applying voltage to the cable insulation defect sample until partial discharge occurs after the temperature of the defect position is stable, and collecting partial discharge data; establishing a heat conduction model and a partial discharge model, and performing coupling to obtain a temperature and partial discharge combined model; and inputting the material parameters, the temperature and the partial discharge data of the cable to be detected into the temperature and partial discharge combined model to obtain the partial discharge characteristics of the cable to be detected. The dynamic influence of the temperature on the parameters of the insulating material can be quantified, so that the accuracy of cable partial discharge characteristic testing is improved.

Description

Background Art

[0002] In recent years, with the growth of power demand, the load rate of high-voltage cables has been continuously increasing, resulting in an increase in cable temperature, which accelerates the insulation aging of the cables and induces partial discharge. There is a complex interaction between temperature and partial discharge. Some studies have shown that an increase in temperature will reduce the inception voltage of partial discharge.

[0003] In the prior art, the partial discharge characteristics of high-voltage cables are usually measured by the pulse current method, the oscillating wave test method, the ultrasonic detection method, and the ultra-high frequency method. Among them, the pulse current method couples the partial discharge signal through a capacitor to measure the apparent discharge amount; the oscillating wave test method analyzes the discharge current pulse signal of the cable after charging to judge the position and size of the partial discharge; the ultrasonic detection method uses the ultrasonic signal generated by the partial discharge to locate the discharge position; the ultra-high frequency method locates by detecting the ultra-high frequency electromagnetic wave (300 MHz - 3 GHz) generated by the partial discharge.

[0004] However, in the above technical solutions, only the influence of voltage on the partial discharge characteristics of high-voltage cables is considered, and the influence of temperature change on the parameters of insulating materials is not considered, so the partial discharge characteristics of high-voltage cables cannot be accurately measured.

[0005] Therefore, it is necessary to improve one or more problems existing in the above related technical solutions.

[0006] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0007] The purpose of the embodiments of the present disclosure is to provide a method and system for testing the partial discharge characteristics of cables based on the combined action of electricity and heat, so as to overcome at least to some extent one or more problems caused by the limitations and defects of the related art.

[0008] In a first aspect, the present application provides a method for testing the partial discharge characteristics of cables based on the combined action of electricity and heat, including: Fabricate a cable insulation defect sample; the cable insulation defects include air gap defects and semi-conductive layer protrusion defects; Apply a load current to the cable insulation defect sample. When the temperature at the defect position is stable, apply a voltage to the cable insulation defect sample until partial discharge occurs, and collect partial discharge data. The partial discharge data includes: defect type, defect position temperature, partial discharge inception voltage, discharge amount of partial discharge, and partial discharge phase spectrum diagram; Establish a heat conduction model and a partial discharge model, and couple them to obtain a temperature and partial discharge joint model; Input the material parameters, temperature, and partial discharge data of the cable to be measured into the combined temperature and partial discharge model to obtain the partial discharge characteristics of the cable to be measured.

[0009] In a possible implementation, the step of fabricating a cable insulation defect sample includes: Place cross-linked polyethylene particles and a polished metal rod in a metal mold, or preset a semiconductive material in the metal mold and then add cross-linked polyethylene particles; Conduct cross-linking treatment on the metal mold through vacuum heating; Demold the metal mold containing the preset semiconductive material and cross-linked polyethylene particles to obtain a semiconductive layer protrusion defect sample, or demold the metal mold containing the metal rod and cross-linked polyethylene particles and then remove the metal rod to obtain a gas gap defect sample.

[0010] In a possible implementation, the step of applying a load current to the cable insulation defect sample, and when the temperature at the defect location is stable, applying a voltage to the cable insulation defect sample until partial discharge occurs and collecting partial discharge data includes: Apply a load current to the cable insulation defect sample until the temperature on the cable surface and the temperature at the defect location are stable, and obtain the temperature change data of the cable surface and the defect location; After controlling the ambient temperature of the cable insulation defect sample to the stable value of the temperature at the defect location, apply a voltage to the cable insulation defect sample until partial discharge occurs and collect partial discharge data.

[0011] In a possible implementation, the step of establishing a heat conduction model and a partial discharge model and coupling them to obtain a combined temperature and partial discharge model includes: Establish a heat conduction model and a partial discharge model; Establish a relationship model between temperature and material parameters, including: a material resistance equation reflecting the change of resistance with temperature, a material relative permittivity equation reflecting the change of relative permittivity with temperature, and a material dielectric loss equation reflecting the change of material dielectric loss angle with temperature; Couple the heat conduction model, the partial discharge model, and the temperature and material parameter relationship model to obtain a combined temperature and partial discharge model.

[0012] In a possible implementation, the heat conduction model includes: a heat conduction equation, a Joule loss equation, and a dielectric loss equation; The heat conduction equation is: ; The Joule loss equation is: ; The dielectric loss equation is: ; Among them, is the material density, is the specific heat capacity at constant pressure, is the temperature, is the time, is the total, is the joule loss, is the dielectric loss, is the material thermal conductivity, is the partial discharge current, is the material resistance, is the power supply frequency, is the capacitance, is the applied voltage, is the tangent of the dielectric loss angle.

[0013] In a possible implementation manner, the partial discharge model includes: a partial discharge current equation, a tunneling effect equation, and a Schottky effect equation; The partial discharge current equation is: ; The tunneling effect equation is: ; The Schottky effect equation is: ; Among them, is the partial discharge current, is the tunneling current, is the Schottky current, is the applied voltage, is the tunneling effect related material parameter that affects the tunneling current by the material, is the tunneling effect related material parameter that reflects the inhibitory effect of the potential barrier on the tunneling current, is the Schottky effect related material parameter that reflects the promoting effect of temperature on the current, is the Schottky effect related material parameter that represents the height of the potential barrier for electron emission, is the temperature, is the Boltzmann constant.

[0014] In a possible implementation manner, the material resistance equation is: ; The relative dielectric constant equation of the material is: ; The material dielectric loss angle equation is: = ; Among them, is the material resistance at the standard temperature, is the resistance temperature coefficient, is the temperature rise value, is the relative dielectric constant of the material, is the standard relative dielectric constant, is the temperature coefficient of relative dielectric constant, is the material dielectric loss angle, is the dielectric loss angle of the standard material, is the temperature coefficient of dielectric loss tangent.

[0015] In a possible implementation, the step of coupling the heat conduction model, the partial discharge model, and the temperature and material parameter relationship model to obtain a temperature and partial discharge joint model includes: Taking temperature as a coupling bridge, the heat conduction model, partial discharge model and the relationship model between temperature and material parameters are combined to obtain the temperature and partial discharge joint model framework; The temperature and partial discharge joint model is obtained by training the partial discharge data and the cable insulation defect sample parameters and optimizing the temperature and partial discharge joint model parameters.

[0016] In a possible implementation, the temperature and partial discharge joint model framework is: ; in, is the cable insulation thickness and defect spacing.

[0017] In a second aspect, the present application provides a cable partial discharge characteristic testing system based on the combined action of electricity and heat, the system is used to perform the above-mentioned cable partial discharge characteristic testing method based on the combined action of electricity and heat, the system comprising: An analog acquisition module is used to apply a load current to the cable insulation defect sample, and when the temperature of the defect position is stable, apply a voltage to the cable insulation defect sample until partial discharge occurs, and collect partial discharge data; Model building module, used to build heat conduction model and partial discharge model, and couple them to obtain temperature and partial discharge joint model; The characteristic calculation module is used to input the material parameters, temperature and partial discharge data of the cable to be tested into the temperature and partial discharge joint model to obtain the partial discharge characteristics of the cable to be tested.

[0018] The technical solution provided by this application may have the following beneficial effects: Through the cable partial discharge characteristic testing method and system based on the combined effect of electricity and heat of the present application, it is possible to obtain the cable parameters at the same time by simulating the temperature and voltage changes in the actual operation of the high-voltage cable; establish a heat conduction model and a partial discharge model, and couple them to obtain a temperature and partial discharge joint model, quantify the dynamic influence of temperature on the parameters of the insulation material, and thus improve the accuracy of the cable partial discharge characteristic testing.

[0019] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and should not limit the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0021] Figure 1 A flowchart showing a method for testing the partial discharge characteristics of a cable based on the combined action of electric and thermal effects in an exemplary embodiment of the present disclosure; Figure 2 A detailed flowchart showing step S100 of the method for testing the partial discharge characteristics of a cable based on the combined action of electric and thermal effects in an exemplary embodiment of the present disclosure; Figure 3 A detailed flowchart showing step S200 of the method for testing the partial discharge characteristics of a cable based on the combined action of electric and thermal effects in an exemplary embodiment of the present disclosure; Figure 4 A detailed flowchart showing step S300 of the method for testing the partial discharge characteristics of a cable based on the combined action of electric and thermal effects in an exemplary embodiment of the present disclosure; Figure 5 A schematic structural diagram showing a system for testing the partial discharge characteristics of a cable based on the combined action of electric and thermal effects in an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more complete and will fully convey the concept of the example embodiments to those skilled in the art. The features, structures, or characteristics described can be combined in any suitable manner in one or more embodiments.

[0023] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0024] In this exemplary embodiment, a method for testing the partial discharge characteristics of a cable based on the combined action of electricity and heat is first provided. This method can be applied to a terminal device, such as a mobile terminal like a mobile phone, a desktop computer, a personal digital assistant, a laptop computer, a tablet computer, a smart watch, etc. Refer to Figure 1 As shown in Step S100: Fabricate a cable insulation defect sample; the cable insulation defects include air gap defects and semi-conductive layer protrusion defects.

[0025] Step S200: Apply a load current to the cable insulation defect sample. When the temperature at the defect location is stable, apply a voltage to the cable insulation defect sample until partial discharge occurs, and collect partial discharge data, which includes: defect type, defect location temperature, partial discharge inception voltage, discharge quantity of partial discharge, and partial discharge phase spectrum diagram.

[0026] Step S300: Establish a heat conduction model and a partial discharge model, and couple them to obtain a temperature and partial discharge joint model.

[0027] Step S400: Input the material parameters, temperature, and partial discharge data of the cable to be tested into the temperature and partial discharge joint model to obtain the partial discharge characteristics of the cable to be tested.

[0028] The above method can fabricate a cable insulation defect sample, apply a current until the temperature of the defect is stable, then apply a voltage until partial discharge occurs, and collect data such as defect type, temperature, partial discharge inception voltage, discharge quantity, and phase spectrum diagram; then establish and couple a heat conduction model and a partial discharge model; finally, input the material parameters of the cable to be tested and partial discharge data, and output its partial discharge characteristics. Thus, through experimental data collection and model coupling analysis, the partial discharge characteristics of the cable can be accurately obtained, providing a scientific basis for cable insulation status assessment, defect type identification, and operation and maintenance, and improving the accuracy and reliability of cable insulation defect diagnosis.

[0029] Next, Figures 1 to 4 each step of the above method in this exemplary embodiment will be described in more detail.

[0030] In step S100, fabricate a cable insulation defect sample; the cable insulation defects include air gap defects and semi-conductive layer protrusion defects.

[0031] It should be noted that the air gap defect is a tiny air gap inside or between layers of solid insulating materials, such as cable insulation layers and GIS insulators, which is usually caused by manufacturing, process or environmental factors, resulting in the air dielectric constant (ε≈1) being much lower than that of insulating materials (such as cross-linked polyethylene ε≈2.3), and the air gap is subjected to a higher partial pressure. When the voltage exceeds the air breakdown field strength (about 3kV / mm), local discharge is triggered, energy is released to corrode the insulation, and electrical dendrites are gradually formed, which eventually break down; the protrusion defect of the semi-conductive layer is a sharp protrusion or unevenness on the surface, which destroys the uniformity of the electric field, has a small curvature radius at the protrusion, and the field strength is concentrated. For example, a 1mm protrusion on a high-voltage conductor can increase the local field strength by 10 times, triggering corona discharge, i.e. local discharge, and long-term discharge leads to local heating, accelerates insulation aging, and even causes penetrating breakdown.

[0032] In one embodiment, Figure 2 As shown, step S100 may include the following sub-steps: In step S110, cross-linked polyethylene particles and a polished metal rod are placed in a metal mold, or cross-linked polyethylene particles are added after a semi-conductive material is preset in the metal mold.

[0033] It should be noted that the metal rod is selected to have a diameter of 3mm, and is polished with sandpaper until the surface is smooth to remove the oxide layer or impurities, and then the metal rod is wiped with alcohol paper to remove surface oil and dust to ensure cleanliness.

[0034] In step S120, the metal mold is cross-linked by vacuum heating.

[0035] It should be noted that, optionally, a mold containing cross-linked polyethylene particles and metal rods / semi-conductive material is placed in a vacuum laminating machine, and the parameters are set to a temperature of 120°C and a pressure of 3 to 5 MPa. The vacuum is drawn and maintained for 10 minutes to allow the cross-linked polyethylene particles to be initially molded in a vacuum environment, and the internal air is discharged to complete preheating; the temperature of the laminating machine is then raised to 180°C, and the pressure is adjusted to 15 MPa; the temperature and pressure are maintained for 30 minutes to allow the cross-linked polyethylene particles to undergo a cross-linking reaction to form a stable insulating structure.

[0036] In step S130, the metal mold containing the preset semiconductive material and cross-linked polyethylene particles is demolded to obtain a semiconductive layer protrusion defect sample, or, after demolding the metal mold containing the metal rod and cross-linked polyethylene particles, the metal rod is removed to obtain an air gap defect sample.

[0037] It should be noted that after the crosslinking is completed, turn off the heating, and wait for the mold to cool naturally or assist with water cooling to accelerate the cooling to room temperature; open the mold to take out the sample, thus completing the demolding, and polish the surface of the sample piece to ensure good electrode contact during subsequent experiments; make an air gap defect, and the metal rod can be removed by chemical dissolution or machining to form a regular air gap.

[0038] In step S200, apply a load current to the cable insulation defect sample. When the temperature at the defect location is stable, apply a voltage to the cable insulation defect sample until partial discharge occurs, and collect partial discharge data. The partial discharge data includes: defect type, temperature at the defect location, partial discharge inception voltage, discharge amount of partial discharge, and partial discharge phase spectrum diagram.

[0039] It can be understood that partial discharge is likely to occur at the defective part of the cable, and the partial discharge data reflects the partial discharge situation at different temperatures and voltages.

[0040] In one embodiment, as Figure 3 shown, step S200 may include the following sub-steps: In step S210, apply a load current to the cable insulation defect sample until the temperature on the cable surface and the temperature at the defect location are stable, and obtain the temperature change data of the cable surface and the defect location.

[0041] It should be noted that different load currents are applied to the cable insulation defect sample, and the changes in the cable surface temperature and the defect location temperature over time are recorded.

[0042] It can be understood that after applying a load current to the cable insulation defect sample, the temperature rise at the defective part will be greater than that of the normal surface. By taking the cable normal surface temperature as an environmental factor, it is judged whether the temperature is stable.

[0043] In step S220, after controlling the environmental temperature of the cable insulation defect sample to the stable value of the temperature at the defect location, apply a voltage to the cable insulation defect sample until partial discharge occurs, and collect partial discharge data.

[0044] It can be understood that at the temperature obtained in step S210, apply a voltage to the cable, and record the partial discharge inception voltage, the discharge amount of partial discharge, and the partial discharge phase spectrum diagram.

[0045] The method of applying voltage is specifically as follows: Pre-boosting: Rise to 1.5 times the rated voltage at a rate of 0.5 kV / s (for example, a 10 kV cable rises to 15 kV) and maintain for 5 minutes to eliminate space charges. Measurement of partial discharge inception voltage (PDIV): Rise the voltage at a rate of 0.2 kV / s and monitor the partial discharge signal through the pulse current method. When the discharge amount exceeds 10 pC and appears continuously for 3 times, record the voltage at this time as PDIV. Recording of discharge amount and phase spectrum: Keep the voltage at 1.5 times PDIV for 30 minutes and synchronously record: Discharge amount: Measured by a high-frequency current transformer with an accuracy of ±5%. Phase spectrum: Combine synchronous acquisition with the voltage phase and use the FFT algorithm to generate a phase distribution from 0 to 360°. The temperature at the defect location is transmitted in real time through an internal fiber optic sensor, and the surface temperature is synchronously recorded by a thermocouple to ensure that the time stamps of the partial discharge signal and the temperature data are aligned.

[0046] In step S300, a heat conduction model and a partial discharge model are established and coupled to obtain a temperature and partial discharge joint model.

[0047] It can be understood that, optionally, using COMSOL Multiphysics software, based on Fourier's law, a cable heat conduction model is established, considering the temperature dependence of dielectric loss and material parameters, and combining the Schottky effect and the tunneling effect, a partial discharge current model under the action of temperature is established, the heat conduction model and the partial discharge model are coupled, a temperature-partial discharge joint equation is established, and the influence of the change of the temperature field on the development of partial discharge is solved.

[0048] In one embodiment, as Figure 4 shown, step S300 may include the following sub-steps: In step S310, a heat conduction model and a partial discharge model are established.

[0049] Optionally, the heat conduction model includes: heat conduction equation, Joule loss equation, dielectric loss equation; The heat conduction equation is: ; The Joule loss equation is: ; The dielectric loss equation is: ; Among them, is the material density, is the specific heat capacity at constant pressure, is the temperature, is the time, is the total, is the Joule loss, is the dielectric loss, is the material thermal conductivity, is the partial discharge current, is the material resistance, is the power supply frequency, is the capacitance, is the applied voltage, is the tangent of the dielectric loss angle.

[0050] Optionally, the partial discharge model includes: a partial discharge current equation, a tunneling effect equation, and a Schottky effect equation; The partial discharge current equation is: ; The tunneling effect equation is: ; The Schottky effect equation is: ; Wherein, is the partial discharge current, is the tunneling current, is the Schottky current, is the applied voltage, is the tunneling effect related material parameter that reflects the influence of the material on the tunneling current, is the tunneling effect related material parameter that reflects the inhibitory effect of the potential barrier on the tunneling current, is the Schottky effect related material parameter that reflects the promoting effect of temperature on the current, is the Schottky effect related material parameter that represents the potential barrier height of electron emission, is the temperature, is the Boltzmann constant.

[0051] It can be understood that the Schottky current is used to describe the influence of temperature on electron emission. When the cable is operating, an increase in temperature will reduce the electron emission potential barrier, enabling more electrons to be emitted from the material surface, forming a discharge current. The tunneling current is used to explain the phenomenon that electrons can penetrate the potential barrier without sufficient thermal energy under a strong electric field. At the cable insulation defects (such as air gaps, tips), the electric field is concentrated, and electrons pass through the potential barrier through quantum tunneling effect, forming a discharge current. The Schottky current reflects temperature dependence, and the tunneling current reflects electric field dependence. The model constructed by combining the two can more accurately match the "thermal-electric coupling" characteristics of cable partial discharge and improve the accuracy of the model's prediction of the discharge current.

[0052] In step S320, a relationship model between temperature and material parameters is established, including: a material resistance equation that reflects the change of resistance with temperature, a material relative dielectric constant equation that reflects the change of relative dielectric constant with temperature, and a material dielectric loss equation that reflects the change of material dielectric loss angle with temperature.

[0053] Optionally, the material resistance equation is: ; The material relative dielectric constant equation is: ; The dielectric loss angle equation of the material is: = ; in, is the material resistance at standard temperature, is the temperature coefficient of resistance, is the temperature rise value, is the relative dielectric constant of the material, is the standard relative dielectric constant, is the temperature coefficient of relative dielectric constant, is the material dielectric loss angle, is the dielectric loss angle of the standard material, is the temperature coefficient of dielectric loss tangent.

[0054] In step S330, the heat conduction model, the partial discharge model and the temperature and material parameter relationship model are coupled to obtain a temperature and partial discharge joint model.

[0055] Further, step S330 may include the following sub-steps: In step S331, the temperature is used as a coupling bridge to combine the heat conduction model, the partial discharge model and the relationship model between temperature and material parameters to obtain a temperature and partial discharge joint model framework.

[0056] The temperature and partial discharge joint model framework is: ; in, is the cable insulation thickness and defect spacing.

[0057] Understandably, The specific meaning needs to be determined in combination with the scenario: Normal insulation structure of the cable: Refers to the thickness of the cable insulation layer, which is used to calculate the overall insulation capacitance and reflects the effect of the insulation layer geometry on the capacitance. Insulation defect scenarios (such as air gaps): It represents the spacing of defects, that is, the distance between the insulating media on both sides of the air gap. It is used to calculate the capacitance of the defect area and reflects the effect of defect geometry on local capacitance, discharge and heat conduction.

[0058] In step S332, the temperature and partial discharge joint model parameters are optimized by training with the partial discharge data and the cable insulation defect sample parameters to obtain the temperature and partial discharge joint model.

[0059] It can be understood that the specific training steps are: 1. Preparation of training data Collect measured data to obtain partial discharge data of cable insulation defect samples under different working conditions (such as measured discharge current ,temperature ), and the measured values of material parameters (such as those measured at different temperatures , , , etc.). Organize the input-output pairs: Construct a training dataset with the input being sample parameters and the output being the measured values of partial discharge current, temperature, and material parameters. 2. Initialize the model parameters by assigning initial values to the unknown parameters in the model. The initial values can be based on empirical formulas, literature data, or random assignment. 3. Iterative calculation and error evaluation. First, perform forward calculation by substituting the current parameters into the model to calculate the partial discharge current and material parameters. Calculate the temperature distribution through the heat conduction equation, then update the material parameters based on the temperature, and finally feedback to the partial discharge model to complete a full coupling calculation. Then, perform error calculation by calculating the error between the simulated value and the measured value, usually using the mean square error (MSE). 4. Parameter optimization and update. Use an optimization algorithm to adjust the parameters. The gradient descent method or genetic algorithm can be selected for calculation. The gradient descent method calculates the gradient of the error with respect to each parameter and updates the parameters along the opposite direction of the gradient, such as . The genetic algorithm encodes the parameters as "chromosomes" and selects the parameter combination that minimizes the error through selection, crossover, and mutation operations. Repeat the steps of iterative calculation, error evaluation, and parameter optimization and update until the error converges (such as the MSE is less than the preset threshold, or the error change rate is <1% for consecutive multiple iterations). 5. Model verification and output. Verify the model accuracy using test data that has not participated in training. If the simulation results match the measured data well (such as the error <5%), then save the optimized parameters, and finally obtain the trained joint model of temperature and partial discharge.

[0060] Furthermore, in this exemplary embodiment, a test system for the partial discharge characteristics of a cable based on the combined electro-thermal effect is also provided. Referring to Figure 5 shown in, the system may include:

[0061] A model establishment module for establishing a heat conduction model and a partial discharge model and coupling them to obtain a joint model of temperature and partial discharge.

[0062] A characteristic calculation module for inputting the material parameters, temperature, and partial discharge data of the cable to be tested into the joint model of temperature and partial discharge to obtain the partial discharge characteristics of the cable to be tested.

[0063] Among them, the simulation acquisition module includes: a power frequency high-voltage unit for providing a stable power frequency high voltage; a current unit for adjusting the current magnitude; a temperature control unit for controlling the ambient temperature around the cable; and a data acquisition unit for real-time acquisition of partial discharge data, where the partial discharge data includes defect type, defect location temperature, partial discharge inception voltage, discharge amount of partial discharge, and partial discharge phase spectrum diagram.

[0064] It should be noted that, optionally, the power frequency high-voltage module is composed of a voltage regulator, a test transformer, and a capacitive voltage divider, with an output voltage range of 0 to 100 kV and a frequency of 50 Hz; the current module is composed of a voltage regulator, a current booster, and a current transformer, with an output current range of 0 to 1000 A; the temperature control module uses a hot air oven, with a temperature control range of -10°C to 200°C and an accuracy of ±1°C; the data acquisition module uses a high-speed data acquisition card, with a sampling frequency of not less than 10 MHz, and is connected to a thermocouple temperature sensor and a high-frequency current transformer (HFCT) for partial discharge signal acquisition.

[0065] Regarding the device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment related to the method, and will not be elaborated here.

[0066] It should be noted that although several modules or units of the device for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiments of the present disclosure, the features and functions of the two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units. The components shown as modules or units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the present disclosure solution. Those of ordinary skill in the art can understand and implement it without creative work.

[0067] In an exemplary embodiment of the present disclosure, an electronic device is further provided. The electronic device may include a processor and a memory for storing executable instructions of the processor. Among them, the processor is configured to execute the steps of the method for testing the partial discharge characteristics of a cable based on the combined action of electrothermal in any one of the above embodiments by executing the executable instructions.

[0068] Those skilled in the art can understand that various aspects of the present invention can be implemented as a system, a method, or a program product. Therefore, various aspects of the present invention can be specifically implemented in the following forms, namely: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or an implementation combining hardware and software aspects, which can be collectively referred to as "circuit", "module", or "system" here.

[0069] Through the description of the above embodiments, those skilled in the art can easily understand that the exemplary embodiments described herein can be implemented by software or by a combination of software and necessary hardware. Therefore, the technical solutions according to the embodiments of the present disclosure can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, a USB flash drive, a mobile hard disk, etc.) or on a network, including several instructions to cause a computing device (which can be a personal computer, a server, or a network device, etc.) to execute the above-mentioned method for testing the partial discharge characteristics of a cable based on the combined action of electrothermal according to the embodiments of the present disclosure.

[0070] In an exemplary embodiment of the present disclosure, there is also provided a computer storage medium having a computer program stored thereon, and when the program is executed by, for example, a processor, the steps of the method for testing the partial discharge characteristics of a cable based on the combined action of electrothermal described in any one of the above embodiments can be implemented.

[0071] In some possible implementation manners, various aspects of the present invention can also be implemented in the form of a computer program product, which includes a computer program or instructions. When the computer program product runs on a terminal device, the computer program code or instructions are used to cause the terminal device to execute the steps according to various exemplary embodiments of the present invention described in the above-mentioned part of the method for testing the partial discharge characteristics of a cable based on the combined action of electrothermal in this specification.

[0072] The above program product can be written in any combination of one or more programming languages for the program code to perform the operations of the present invention. The programming languages include object-oriented programming languages - such as Java, C++, etc., and also include conventional procedural programming languages - such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computing device, partially on the user's device, executed as an independent software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device can be connected to the user's computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computing device (for example, by using an Internet service provider to connect through the Internet).

[0073] The computer software product can be stored in a computer storage medium, which includes read-only memory (ROM), random access memory (RAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), one-time programmable read-only memory (OTPROM), electrically-erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc memories, magnetic disc memories, magnetic tape memories, or any other medium that is computer-readable and can be used to carry or store data.

[0074] Those skilled in the art will readily conceive of other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include known common general knowledge or conventional technical means in the technical field not disclosed in the present disclosure. The specification and examples are only regarded as exemplary, and the true scope and spirit of the present disclosure are pointed out by the appended claims.

Claims

1. A method for testing the partial discharge characteristics of cables based on the combined action of electricity and heat, characterized in that: include: Making a cable insulation defect sample; the cable insulation defect includes an air gap defect and a semi-conductive layer protrusion defect; Applying a load current to the cable insulation defect sample, and when the temperature of the defect position is stable, applying a voltage to the cable insulation defect sample until partial discharge occurs, and collecting partial discharge data, the partial discharge data including: defect type, defect position temperature, partial discharge starting voltage, partial discharge discharge amount and partial discharge phase spectrum; Establish a heat conduction model and a partial discharge model, and couple them to obtain a temperature and partial discharge joint model; The material parameters, temperature and partial discharge data of the cable under test are input into the temperature and partial discharge joint model to obtain the partial discharge characteristics of the cable under test.

2. The cable partial discharge characteristic testing method based on the combined action of electricity and heat according to claim 1 is characterized in that: The step of preparing the cable insulation defect sample comprises: Put cross-linked polyethylene particles and a polished metal rod in a metal mold, or, pre-place a semi-conductive material in the metal mold and then add the cross-linked polyethylene particles; Cross-linking of metal molds by vacuum heating; The metal mold containing the preset semiconductive material and cross-linked polyethylene particles is demolded to obtain a semiconductive layer protrusion defect sample, or, after demolding the metal mold containing the metal rod and cross-linked polyethylene particles, the metal rod is removed to obtain an air gap defect sample.

3. The cable partial discharge characteristic testing method based on the electric and thermal combined action according to claim 1 is characterized in that: The step of applying a load current to the cable insulation defect sample, applying a voltage to the cable insulation defect sample until partial discharge occurs when the temperature of the defect position is stable, and collecting partial discharge data, wherein the step of collecting partial discharge data comprises: Applying a load current to the cable insulation defect sample until the cable surface temperature and the defect location temperature are stable, and obtaining the cable surface temperature and the defect location temperature change data; After controlling the ambient temperature of the cable insulation defect sample to a stable temperature value at the defect position, applying voltage to the cable insulation defect sample to cause partial discharge, and collecting partial discharge data.

4. The cable partial discharge characteristic testing method based on the combined action of electricity and heat according to claim 1 is characterized in that: The step of establishing a heat conduction model and a partial discharge model, and coupling them to obtain a temperature and partial discharge joint model includes: Establish heat conduction model and partial discharge model; Establish a temperature and material parameter relationship model, including: material resistance equation for the reaction resistance changing with temperature, material relative dielectric constant equation for the reaction relative dielectric constant changing with temperature, and material dielectric loss equation for the reaction material dielectric loss angle changing with temperature; The heat conduction model, partial discharge model and the temperature and material parameter relationship model are coupled to obtain a temperature and partial discharge joint model.

5. The cable partial discharge characteristic testing method based on the combined action of electricity and heat according to claim 4 is characterized in that: The heat conduction model includes: a heat conduction equation, a Joule loss equation, and a dielectric loss equation; The heat conduction equation is: ; The Joule loss equation is: ; The dielectric loss equation is: ; in, is the material density, is the specific heat capacity at constant pressure, is the temperature, For time, For total, is the Joule loss, is the dielectric loss, is the thermal conductivity of the material, is the partial discharge current, is the material resistance, is the power frequency, is the capacitance, To apply voltage, is the dielectric loss tangent.

6. The cable partial discharge characteristic testing method based on the electric and thermal combined action according to claim 5 is characterized in that: The partial discharge model includes: a partial discharge current equation, a tunneling effect equation and a Schottky effect equation; The partial discharge current equation is: ; The tunneling effect equation is: ; The Schottky effect equation is: ; in, is the partial discharge current, is the tunneling current, is the Schottky current, To apply voltage, is the material parameter related to the tunneling effect that affects the tunneling current, To reflect the tunneling effect related material parameters that reflect the inhibitory effect of the potential barrier on the tunneling current, To reflect the Schottky effect related material parameters that promote the current through temperature, is the Schottky effect related material parameter representing the barrier height for electron escape, is the temperature, is the Boltzmann constant.

7. The cable partial discharge characteristic testing method based on the electric and thermal combined action according to claim 6 is characterized in that: The material resistance equation is: ; The relative dielectric constant equation of the material is: ; The dielectric loss angle equation of the material is: = ; in, is the material resistance at standard temperature, is the temperature coefficient of resistance, is the temperature rise value, is the relative dielectric constant of the material, is the standard relative dielectric constant, is the temperature coefficient of relative dielectric constant, is the material dielectric loss angle, is the dielectric loss angle of the standard material, is the temperature coefficient of dielectric loss tangent.

8. The cable partial discharge characteristic testing method based on the combined action of electricity and heat according to claim 7 is characterized in that: The step of coupling the heat conduction model, the partial discharge model and the temperature and material parameter relationship model to obtain a temperature and partial discharge joint model includes: Taking temperature as a coupling bridge, the heat conduction model, partial discharge model and the relationship model between temperature and material parameters are combined to obtain the temperature and partial discharge joint model framework; The temperature and partial discharge joint model is obtained by training the partial discharge data and the cable insulation defect sample parameters and optimizing the temperature and partial discharge joint model parameters.

9. The cable partial discharge characteristic testing method based on the electric and thermal combined action according to claim 8 is characterized in that: The temperature and partial discharge joint model framework is: ； in, is the cable insulation thickness and defect spacing.

10. A cable partial discharge characteristic test system based on electric and thermal combined action, characterized in that: The system is used to execute the method according to any one of claims 1 to 9, and the system comprises: An analog acquisition module is used to apply a load current to the cable insulation defect sample, and when the temperature of the defect position is stable, apply a voltage to the cable insulation defect sample until partial discharge occurs, and collect partial discharge data; Model building module, used to build heat conduction model and partial discharge model, and couple them to obtain temperature and partial discharge joint model; The characteristic calculation module is used to input the material parameters, temperature and partial discharge data of the cable to be tested into the temperature and partial discharge joint model to obtain the partial discharge characteristics of the cable to be tested.

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