High-voltage cable insulation tree-DCIC characteristic joint detection method and system

Abstract

A method and system for joint detection of electrical tree-DCIC characteristics of high-voltage cable insulation, including placing an insulating material sample on a measurement experimental platform and collecting images of the sample during the experiment; based on a time-division multiplexing strategy, applying high-voltage AC voltage and high-voltage DC voltage alternately to the insulating material sample, and performing electrical tree degradation and DCIC-Q(t) measurements alternately during the voltage application process; collecting morphological data of electrical tree degradation and characteristic data of DCIC-Q(t) measurements during the experiment to form a test data set for the performance of the insulating material; using the test data set for the performance of the insulating material as the input of the model, and using a trained insulating material performance test model to output the test results of the performance of the insulating material. By synchronously measuring the DCIC characteristics of the insulating medium during the electrical tree degradation process, the charge dynamic characteristics of the insulating material during the electrical tree degradation process are obtained, and the performance of the insulating material for the high-voltage cable can be evaluated by this method.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical engineering high voltage and insulation material performance testing, and in particular relates to a method and system for joint detection of high voltage cable insulation DCIC characteristics. Background Art

[0002] High-voltage cable transmission has the advantages of large transmission capacity, long distance, high efficiency and low loss. It is a reliable technical means to meet the needs of large-capacity, long-distance cross-regional power transmission. It is also the best means to solve problems such as urban power grid capacity expansion, new energy grid connection and offshore island power supply.

[0003] The Direct Current Integrated Charge (DCIC) method is an effective detection method for obtaining the dynamic characteristics of charge in insulating dielectric materials. Its principle is to integrate the leakage current in the insulating medium to obtain characteristic parameters such as dielectric constant, space charge, dielectric conductivity, dielectric relaxation time constant, and carrier mobility.

[0004] Prior art 1 (CN113376483A) "A method for evaluating the insulation state of XLPE cables" uses DCIC-q(t) technology to test the dynamic change parameters of the charge of the cable to be tested, extracts the conductivity of the insulating medium of the cable to be tested according to the dynamic change parameters of the charge, establishes a neural network model of dynamic charge parameter distribution, obtains the insulation state of the cable to be tested, establishes a BP neural network and FCM XLPE cable insulation aging state evaluation model, and inputs the dynamic change parameters of the charge into the BP neural network and FCM XLPE cable insulation aging state evaluation model. Prior art 1 extracts the dynamic change parameters of the charge, and uses the fuzzy C-means clustering (FCM) method to classify and determine the insulation state. The proposed evaluation model can improve the accuracy of the cable insulation aging state evaluation. Among them, the DCIC-q(t) technical testing method includes: controlling the voltage of the high-voltage DC source through the terminal; detecting the current passing through the sample through the integral capacitor, integrating and obtaining the charge information, and transmitting it to the zigbee receiver through AD conversion; the zigbee receiver receives the signal wave, and analyzes and processes the data to transmit the processing results. However, the DCIC-q(t) technology in the prior art 1 tests the dynamic change parameters of the charge of the cable to be tested not only for the insulation degradation process, but also the electrical tree degradation phenomenon of the high-voltage cable insulation material is the core factor threatening the insulation reliability, and the generation and development of the electrical tree degradation of the insulation material is closely related to the charge dynamics within the insulation material. Therefore, detecting the charge dynamic characteristics during the generation and development of the electrical tree degradation is of great significance to the performance evaluation of the insulation material. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a method and system for joint detection of electrical tree-DCIC characteristics of high-voltage cable insulation, by synchronously measuring the DCIC characteristics of the insulating medium during electrical tree degradation, and obtaining the charge dynamic characteristics of the insulating material during electrical tree degradation, thereby realizing the evaluation of the performance of the insulating material for the high-voltage cable.

[0006] The present invention adopts the following technical solution.

[0007] In one aspect, the present invention provides a method for joint detection of high voltage cable insulation electrical tree-DCIC characteristics, comprising:

[0008] Step 1, placing the insulating material sample on the measurement experimental platform;

[0009] Step 2, based on a time division multiplexing strategy, a high voltage AC voltage and a high voltage DC voltage are alternately applied to the insulating material sample, and electrical tree degradation and DCIC-Q(t) measurements are alternately performed during the voltage application process;

[0010] Step 3, repeating step 2 for a set number of cycles, collecting morphological image data of electrical tree degradation during the experiment, and using DCIC-Q(t) measurement technology to collect DCIC-Q(t) feature data; the degradation morphological image data and DCIC-Q(t) feature data constitute a test data set for the performance of the insulating material;

[0011] Step 4: Using the test data set of the insulation material performance as the input of the model, the trained insulation material performance test model is used to output the insulation material performance test results.

[0012] Preferably, step 2 comprises:

[0013] Step 2.1, applying a high voltage AC voltage with an effective value of not less than 6 kV and a duration of not less than 10 min to the insulating material sample; when the high voltage AC voltage is applied, performing electrical tree degradation on the insulating material sample;

[0014] Step 2.2, applying a high voltage DC voltage with a voltage value of not less than 3 kV and a duration of not less than 5 min to the insulating material sample; when the high voltage DC voltage is applied, performing DCIC-Q(t) measurement on the insulating material sample.

[0015] Preferably, in step 3, the set number of cycles is not less than 4.

[0016] Preferably, in step 3, the DCIC-Q(t) characteristic data includes: the equivalent capacitance C of the insulating sample a , space charge Q sc , Conductivity of insulation sample G a, relaxation time constant τ, carrier mobility μ.

[0017] Preferably, the insulating sample equivalent capacitance C a Satisfies the following relationship:

[0018] ∫I char (t)dt=Q0=C a U DC

[0019] In the formula,

[0020] I char (t) is the charging current, which represents the displacement current that charges the electrode and establishes the electric field.

[0021] Q0 is the charge on the electrode that is accumulated by the charging current to form the capacitor, that is, the initial charge.

[0022] U DC is a DC voltage.

[0023] Preferably, the space charge Q sc Satisfies the following relationship:

[0024]

[0025] In the formula,

[0026] I abs (t) is the absorption current, which includes the current of the insulating medium polarization process and the charge injection process, and has a decay characteristic.

[0027] Q sc It is the amount of space charge inside the insulating medium, including the polarization charge generated by the polarization of the insulating medium and the charge injected by the electrode under high electric field strength.

[0028] Preferably, the insulation sample conductivity G a Satisfies the following relationship:

[0029] ∫I cond (t)dt=U DC G a t

[0030] In the formula,

[0031] I cond (t) is the conductance current, which represents the DC conductivity of the insulating medium.

[0032] U DC is a DC voltage.

[0033] Preferably, the relaxation time constant τ satisfies the following relationship:

[0034]

[0035] In the formula,

[0036] I abs (t) is the absorption current, which includes the current of the insulating medium polarization process and the charge injection process, and has a decay characteristic.

[0037] Q sc It is the amount of space charge inside the insulating medium, including the polarization charge generated by the polarization of the insulating medium and the charge injected by the electrode under high electric field strength.

[0038] Preferably, the carrier mobility μ satisfies the following relationship:

[0039]

[0040] In the formula,

[0041] J is the current density in the insulating sample,

[0042] d is the thickness of the insulating sample,

[0043] E is the applied DC electric field strength,

[0044] ε0 is the dielectric constant of vacuum, ε0=8.865×10 -12 F / m,

[0045] ε r is the relative dielectric constant, which depends on the material of the insulating material to be tested.

[0046] Preferably, the leakage current integrated charge Q(t) can be expressed as the sum of three partial charges, satisfying the following relationship:

[0047] Q(t)=∫I char (t)dt+∫I abs (t)dt+∫I cond (t)dt

[0048] In the formula, the charging current I char (t), absorption current I abs (t) and the conduction current I cond The sum of (t) is the response current I(t) under the action of high voltage DC voltage, where the high voltage DC voltage is a step voltage.

[0049] Preferably, in step 4, the insulation material performance test model is a neural network-based model, including an input layer, three hidden layers and an output layer;

[0050] The insulation material performance test model is trained by machine learning process to obtain the mapping relationship between DCIC-Q(t) characteristic data and insulation material performance. The parameter configuration of each layer is determined based on the mapping relationship to obtain a trained insulation material performance test model.

[0051] On the other hand, the present invention also proposes a high-voltage cable insulation electrical tree-DCIC characteristic joint detection system, comprising: a measurement experimental platform, a first time division multiplexing module, a second time division multiplexing module, a high-voltage DC power supply, a high-voltage AC power supply, a DCIC-Q(t) measurement module, and an image acquisition module;

[0052] Measuring experimental platform, used to place insulating material samples;

[0053] A first time division multiplexing module, one end of which is connected to the measurement experimental platform, and the other end of which is respectively connected to a high-voltage DC power supply and a high-voltage AC power supply; the first time division multiplexing module is used to alternately apply a high-voltage AC voltage and a high-voltage DC voltage to the insulating material sample based on a time division multiplexing strategy;

[0054] A second time division multiplexing module, one end of which is connected to the measurement experimental platform, and the other end of which is respectively connected to the first ground terminal and the DCIC-Q(t) measurement module; the second time division multiplexing module is used to perform electrical tree degradation on the insulating material sample in the process of applying the high-voltage AC voltage according to the time division signal provided by the first time division multiplexing module, and perform DCIC-Q(t) measurement on the insulating material sample in the process of applying the high-voltage DC voltage;

[0055] The image acquisition module is used to collect image data of insulating material samples during the experiment.

[0056] Preferably, when the first time division multiplexing module connects one end of the insulating material sample to the high voltage AC voltage, the second time division multiplexing module grounds the other end of the insulating material sample through the first grounding end.

[0057] Preferably, when the first time division multiplexing module connects one end of the insulating material sample to a high voltage DC voltage, the second time division multiplexing module connects the other end of the insulating material sample to a DCIC-Q(t) measurement module, and the DCIC-Q(t) measurement module is used to collect DCIC-Q(t) measurement characteristic data of the insulating material sample when electrical tree degradation occurs; wherein the DCIC-Q(t) measurement module is grounded through the second grounding terminal.

[0058] Preferably, the images of the insulating material sample collected by the image collection module during the experiment include: morphological image data of electrical tree degradation of the insulating material sample.

[0059] The beneficial effects of the present invention are as follows:

[0060] 1. Accurately measure the charge dynamic characteristics in the insulating material during the generation and development of electrical tree degradation of the insulating material, detect and evaluate the performance of the insulating material based on the charge dynamic characteristics, and realize the joint evaluation of the insulating medium performance based on the electrical tree growth characteristics and DCIC characteristic parameters, thereby improving the credibility of the test results;

[0061] 2. Through DCIC-Q(t) measurement, the leakage current integrated charge characteristics of the insulation material can be divided into stages, which is conducive to quantitative evaluation of the degree of insulation material degradation, and to provide insulation material degradation early warning and degradation development trend prediction according to the stage of the leakage current integrated charge characteristics;

[0062] 3. Collecting the morphological image data of electrical tree degradation of insulating material samples is helpful to verify the accuracy of performance testing of insulating material samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a flowchart of the steps of the combined detection method of the insulation tree-DCIC characteristics of high-voltage cables of the present invention;

[0064] Figure 2 is a structural schematic diagram of an insulation material performance test model in one embodiment of the present invention;

[0065] Figure 3 It is a structural schematic diagram of the high-voltage cable insulation electrical tree-DCIC characteristic joint detection system of the present invention;

[0066] Figure 3 The reference numerals in the drawings are described as follows:

[0067] 1-measurement experiment platform; 21-first time division multiplexing module; 22-second time division multiplexing module; 31-high voltage DC power supply; 32-high voltage AC power supply; 4-DCIC-Q(t) measurement module; 5-image acquisition module; 61-first ground terminal; 62-second ground terminal;

[0068] Figure 4 is a graph showing the electrical tree degradation morphology of the insulating material and the DCIC test result in one embodiment of the present invention;

[0069] Figure 5 1 is a morphological image of electrical tree degradation of an insulating material under different test cycles in one embodiment of the present invention. DETAILED DESCRIPTION

[0070] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present application.

[0071] like Figure 1On the one hand, the present invention proposes a joint detection method for high-voltage cable insulation electrical tree-DCIC characteristics, including steps 1 to 4.

[0072] Step 1: Place the insulating material sample on the measurement experimental platform.

[0073] Step 2: Based on the time division multiplexing strategy, high voltage AC voltage and high voltage DC voltage are alternately applied to the insulating material sample, and electrical tree degradation and DCIC-Q(t) measurements are alternately performed during the voltage application process.

[0074] Preferably, step 2 comprises:

[0075] Step 2.1, applying a high voltage AC voltage with an effective value of not less than 6 kV and a duration of not less than 10 min to the insulating material sample; when the high voltage AC voltage is applied, the insulating material sample is subjected to electrical tree degradation.

[0076] Step 2.2, applying a high voltage DC voltage with a voltage value of not less than 3 kV and a duration of not less than 5 min to the insulating material sample; when the high voltage DC voltage is applied, performing DCIC-Q(t) measurement on the insulating material sample.

[0077] It is worth noting that in the preferred embodiment of the present invention, the voltage value and duration of the high-voltage AC voltage and the high-voltage DC voltage are a non-restrictive and preferred choice. Those skilled in the art can apply high-voltage AC voltage or high-voltage DC voltage of different voltage values ​​and durations to the insulating material sample according to requirements such as the accuracy of the insulation test.

[0078] Step 3, repeat step 2 for a set number of cycles, collect morphological image data of electrical tree degradation during the experiment, and use DCIC-Q(t) measurement technology to collect DCIC-Q(t) feature data; the degradation morphological image data and DCIC-Q(t) feature data constitute a test data set for the performance of the insulating material.

[0079] Preferably, in step 3, the number of cycles is set to be no less than 4. It should be noted that in the preferred embodiment of the present invention, the number of cycles is set to be no less than 4, which is a non-limiting and preferred choice.

[0080] Preferably, in step 3, the DCIC-Q(t) characteristic data includes: the equivalent capacitance C of the insulating sample a , space charge Q sc , Conductivity of insulation sample G a , relaxation time constant τ, carrier mobility μ.

[0081] Based on the insulation medium response theory, the response current I(t) under the action of high voltage DC voltage in the form of step voltage satisfies the following relationship:

[0082] I(t)=I char (t)+I abs (t)+I cond (t)

[0083] In the formula,

[0084] I char (t) is the charging current, which represents the displacement current that charges the electrode and establishes the electric field,

[0085] I abs (t) is the absorption current, which includes the current of the insulating medium polarization process and the charge injection process, and has a decay characteristic

[0086] I cond (t) is the conductance current, which characterizes the DC conductivity of the insulating medium. Therefore, the leakage current integral charge Q(t) can be expressed as the sum of the three partial charges, satisfying the following relationship:

[0087] Q(t)=∫I char (t)dt+∫I abs (t)dt+∫I cond (t)dt

[0088] Furthermore, the following relationship is satisfied for the charging current component:

[0089] ∫I char (t)dt=Q0=C a U DC

[0090] In the formula,

[0091] C a is the equivalent capacitance of the insulating sample,

[0092] I char (t) is the charging current, which represents the displacement current that charges the electrode and establishes the electric field.

[0093] Q0 is the charge on the electrode that is accumulated by the charging current to form the capacitor, that is, the initial charge.

[0094] U DC is a DC voltage.

[0095] Furthermore, the following relationship is satisfied for the absorption current component:

[0096]

[0097] In the formula,

[0098] Q sc is the space charge,

[0099] Iabs (t) is the absorption current, which includes the current of the insulating medium polarization process and the charge injection process, and has a decay characteristic.

[0100] Q sc It is the amount of space charge inside the insulating medium, including the polarization charge generated by the polarization of the insulating medium and the charge injected by the electrode under high electric field strength.

[0101] Furthermore, the absorption current attenuation law conforms to a negative exponential function, so the integral value of the absorption current can be expressed by a negative exponential function, satisfying the following relationship:

[0102]

[0103] In the formula,

[0104] τ is the relaxation time constant,

[0105] I abs (t) is the absorption current, which includes the current of the insulating medium polarization process and the charge injection process, and has a decay characteristic.

[0106] Q sc It is the amount of space charge inside the insulating medium, including the polarization charge generated by the polarization of the insulating medium and the charge injected by the electrode under high electric field strength.

[0107] Furthermore, the DC conduction current component satisfies the following relationship:

[0108] ∫I cond (t)dt=U DC G a t

[0109] In the formula,

[0110] G a is the conductivity of the insulating sample,

[0111] I cond (t) is the conductance current, which represents the DC conductivity of the insulating medium.

[0112] U DC is a DC voltage.

[0113] Furthermore, the carrier mobility μ satisfies the following relationship:

[0114]

[0115] In the formula,

[0116] J is the current density in the insulating sample,

[0117] d is the thickness of the insulating sample,

[0118] E is the applied DC electric field strength,

[0119] ε0 is the dielectric constant of vacuum, ε0=8.865×10 -12 F / m,

[0120] ε r is the relative dielectric constant, which depends on the material of the insulating material to be tested.

[0121] The typical results of DCIC-Q(t) for insulating dielectric materials can be described in three parts, as follows:

[0122] (i) Initial charge accumulation stage. This stage lasts for a short time. After the electric field is applied, charges accumulate instantly at both ends of the electrode to form a capacitor.

[0123] (ii) Absorption charge accumulation stage, in which the charge accumulation shows a negative exponential increase, and the charge forms a polarized electric field inside the insulating medium;

[0124] (iii) Conductivity stage: In this stage, the absorption current has decayed, the leakage current is a DC conduction current, and the integrated charge accumulation shows a linear upward trend.

[0125] Step 4: Using the test data set of the insulation material performance as the input of the model, the trained insulation material performance test model is used to output the insulation material performance test results.

[0126] Preferably, in step 4, Figure 2 The insulation material performance test model is a neural network-based model, which includes an input layer, three hidden layers and an output layer.

[0127] The insulation material performance test model is trained by machine learning process to obtain the mapping relationship between DCIC-Q(t) characteristic data and insulation material performance. The parameter configuration of each layer is determined based on the mapping relationship to obtain a trained insulation material performance test model.

[0128] Another aspect of the present invention is to provide a high voltage cable insulation tree-DCIC characteristic joint detection system, such as Figure 3 , including: a measurement experimental platform 1, a first time division multiplexing module 21, a second time division multiplexing module 22, a high-voltage DC power supply 31, a high-voltage AC power supply 32, a DCIC-Q(t) measurement module 4, and an image acquisition module 5.

[0129] The measuring experimental platform 1 is used for placing insulating material samples.

[0130] The first time division multiplexing module 21 has one end connected to the measurement experiment platform 1 and the other end connected to the high-voltage DC power supply 31 and the high-voltage AC power supply 32 respectively; the first time division multiplexing module 21 is used to alternately apply high-voltage AC voltage and high-voltage DC voltage to the insulating material sample based on the time division multiplexing strategy.

[0131] The second time division multiplexing module 22 has one end connected to the measurement experimental platform 1, and the other end connected to the first ground terminal and the DCIC-Q(t) measurement module 4 respectively; the second time division multiplexing module 22 is used to perform electrical tree degradation on the insulating material sample in the process of applying a high-voltage AC voltage according to the time division signal provided by the first time division multiplexing module 21, and perform DCIC-Q(t) measurement on the insulating material sample in the process of applying a high-voltage DC voltage.

[0132] The image acquisition module 5 is used to acquire image data of the insulating material sample during the experiment.

[0133] Preferably, when the first time division multiplexing module 21 connects one end of the insulating material sample to the high voltage AC voltage, the second time division multiplexing module 22 connects the other end of the insulating material sample to the ground through the first grounding terminal 61 .

[0134] Preferably, when the first time division multiplexing module 21 connects one end of the insulating material sample to a high voltage DC voltage, the second time division multiplexing module 22 connects the other end of the insulating material sample to a DCIC-Q(t) measurement module 4, and the DCIC-Q(t) measurement module 4 is used to collect DCIC-Q(t) measurement characteristic data of the insulating material sample when electrical tree degradation occurs; wherein the DCIC-Q(t) measurement module 4 is grounded via the second grounding terminal 62.

[0135] Preferably, the images of the insulating material sample collected by the image collection module 5 during the experiment include: morphological image data of electrical tree degradation of the insulating material sample.

[0136] The insulation material electrical tree degradation morphology and DCIC test result curve obtained by using the high-voltage cable insulation electrical tree-DCIC characteristic joint detection method and system are shown in detail in Figure 4 , the morphological images of insulation material electrical tree degradation under different test cycles are shown in Figure 5 .

[0137] The beneficial effects of the present invention are as follows:

[0138] 1. Accurately measure the charge dynamic characteristics in the insulating material during the generation and development of electrical tree degradation of the insulating material, detect and evaluate the performance of the insulating material based on the charge dynamic characteristics, and realize the joint evaluation of the insulating medium performance based on the electrical tree growth characteristics and DCIC characteristic parameters, thereby improving the credibility of the test results;

[0139] 2. Through DCIC-Q(t) measurement, the leakage current integrated charge characteristics of the insulation material can be divided into stages, which is conducive to quantitative evaluation of the degree of insulation material degradation, and to provide insulation material degradation early warning and degradation development trend prediction according to the stage of the leakage current integrated charge characteristics;

[0140] 3. Collecting the morphological image data of electrical tree degradation of insulating material samples is helpful to verify the accuracy of performance testing of insulating material samples.

[0141] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation schemes of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, but not to limit the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A joint detection method for high voltage cable insulation electrical tree-DCIC characteristics, characterized in that: The method comprises: Step 1, placing the insulating material sample on the measurement experimental platform; Step 2, based on a time division multiplexing strategy, a high voltage AC voltage and a high voltage DC voltage are alternately applied to the insulating material sample, and in the process of applying the high voltage AC voltage, electrical tree degradation is performed on the insulating material sample, and in the process of applying the high voltage DC voltage, DCIC-Q(t) is measured on the insulating material sample; Step 3, repeating step 2 for a set number of cycles, collecting morphological image data of electrical tree degradation during the experiment, and using DCIC-Q(t) measurement technology to collect DCIC-Q(t) feature data; the degradation morphological image data and DCIC-Q(t) feature data constitute a test data set for the performance of the insulating material; Step 4: Using the test data set of the insulation material performance as the input of the model, the trained insulation material performance test model is used to output the insulation material performance test results.

2. The method for joint detection of high-voltage cable insulation electrical tree-DCIC characteristics according to claim 1 is characterized in that: Step 2 includes: Step 2.1, applying a high voltage AC voltage with an effective value of not less than 6 kV and a duration of not less than 10 min to the insulating material sample; when the high voltage AC voltage is applied, performing electrical tree degradation on the insulating material sample; Step 2.2, applying a high voltage DC voltage with a voltage value of not less than 3 kV and a duration of not less than 5 min to the insulating material sample; when the high voltage DC voltage is applied, performing DCIC-Q(t) measurement on the insulating material sample.

3. The method for joint detection of high-voltage cable insulation electrical tree-DCIC characteristics according to claim 1 is characterized in that: In step 3, the number of cycles is set to be no less than 4.

4. The method for joint detection of high-voltage cable insulation electrical tree-DCIC characteristics according to claim 3 is characterized in that: In step 3, the DCIC-Q(t) characteristic data includes: the equivalent capacitance C of the insulation sample a , space charge Q sc , Conductivity of insulation sample G a , relaxation time constant τ, carrier mobility μ.

5. The method for joint detection of high-voltage cable insulation electrical tree-DCIC characteristics according to claim 3 is characterized in that: Insulation sample equivalent capacitance C a Satisfies the following relationship: ∫I char (t)dt=Q0=C a U DC In the formula, I char (t) is the charging current, which represents the displacement current that charges the electrode and establishes the electric field. Q0 is the charge on the electrode that is accumulated by the charging current to form the capacitor, that is, the initial charge. U DC is a DC voltage.

6. The method for joint detection of high-voltage cable insulation electrical tree-DCIC characteristics according to claim 3 is characterized in that: Space charge Q sc Satisfies the following relationship: In the formula, I abs (t) is the absorption current, which includes the current of the insulating medium polarization process and the charge injection process, and has a decay characteristic. Q sc It is the amount of space charge inside the insulating medium, including the polarization charge generated by the polarization of the insulating medium and the charge injected by the electrode under high electric field strength.

7. The method for joint detection of high voltage cable insulation electrical tree-DCIC characteristics according to claim 3 is characterized in that: Insulation sample conductivity G a Satisfies the following relationship: ∫I cond (t)dt=U DC G a t In the formula, I cond (t) is the conductance current, which represents the DC conductivity of the insulating medium. U DC is a DC voltage.

8. The method for joint detection of high-voltage cable insulation electrical tree-DCIC characteristics according to claim 3 is characterized in that: The relaxation time constant τ satisfies the following relationship: In the formula, I abs (t) is the absorption current, which includes the current of the insulating medium polarization process and the charge injection process, and has a decay characteristic. Q sc It is the amount of space charge inside the insulating medium, including the polarization charge generated by the polarization of the insulating medium and the charge injected by the electrode under high electric field strength.

9. The method for joint detection of high voltage cable insulation electrical tree-DCIC characteristics according to claim 3, characterized in that: The carrier mobility μ satisfies the following relationship: In the formula, J is the current density in the insulating sample, d is the thickness of the insulating sample, E is the applied DC electric field strength, ε0 is the dielectric constant of vacuum, ε0=8.865×10 -12 F / m, ε r is the relative dielectric constant, which depends on the material of the insulating material to be tested.

10. The method for joint detection of high voltage cable insulation electrical tree-DCIC characteristics according to any one of claims 5 to 7, characterized in that: The leakage current integrated charge Q(t) can be expressed as the sum of three partial charges, satisfying the following relationship: Q(t)=∫I char (t)dt+∫I abs (t)dt+∫I cond (t)dt In the formula, the charging current I char (t), absorption current I abs (t) and the conduction current I cond The sum of (t) is the response current I(t) under the action of high voltage DC voltage, where the high voltage DC voltage is a step voltage.

11. The method for joint detection of high voltage cable insulation tree-DCIC characteristics according to claim 1, characterized in that: In step 4, the insulation material performance test model is a neural network-based model, including an input layer, three hidden layers and an output layer; The insulation material performance test model is trained by machine learning process to obtain the mapping relationship between DCIC-Q(t) characteristic data and insulation material performance. The parameter configuration of each layer is determined based on the mapping relationship to obtain a trained insulation material performance test model.

12. A high-voltage cable insulation electrical tree-DCIC characteristic joint detection system implemented by using the high-voltage cable insulation electrical tree-DCIC characteristic joint detection method according to any one of claims 1 to 11, characterized in that: The detection system includes: Measurement experimental platform, first time division multiplexing module, second time division multiplexing module, high voltage DC power supply, high voltage AC power supply, DCIC-Q(t) measurement module, image acquisition module; Measuring experimental platform, used to place insulating material samples; A first time division multiplexing module, one end of which is connected to the measurement experimental platform, and the other end of which is respectively connected to a high-voltage DC power supply and a high-voltage AC power supply; the first time division multiplexing module is used to alternately apply a high-voltage AC voltage and a high-voltage DC voltage to the insulating material sample based on a time division multiplexing strategy; A second time division multiplexing module, one end of which is connected to the measurement experimental platform, and the other end of which is respectively connected to the first ground terminal and the DCIC-Q(t) measurement module; the second time division multiplexing module is used to perform electrical tree degradation on the insulating material sample in the process of applying the high-voltage AC voltage according to the time division signal provided by the first time division multiplexing module, and perform DCIC-Q(t) measurement on the insulating material sample in the process of applying the high-voltage DC voltage; The image acquisition module is used to collect image data of insulating material samples during the experiment.

13. The high-voltage cable insulation tree-DCIC characteristic joint detection system according to claim 12, characterized in that: When the first time division multiplexing module connects one end of the insulating material sample to the high voltage AC voltage, the second time division multiplexing module connects the other end of the insulating material sample to the ground via the first grounding end.

14. The high-voltage cable insulation tree-DCIC characteristic joint detection system according to claim 12, characterized in that: When the first time division multiplexing module connects one end of the insulating material sample to a high voltage DC voltage, the second time division multiplexing module connects the other end of the insulating material sample to a DCIC-Q(t) measurement module, and the DCIC-Q(t) measurement module is used to collect DCIC-Q(t) measurement characteristic data of the insulating material sample when electrical tree degradation occurs; wherein the DCIC-Q(t) measurement module is grounded through the second grounding terminal.

15. The high-voltage cable insulation tree-DCIC characteristic joint detection system according to claim 11, characterized in that: The images of the insulating material sample collected by the image acquisition module during the experiment include: morphological image data of the electrical tree degradation of the insulating material sample.

Images