Electric tree real-time observation and ultrahigh frequency partial discharge monitoring combined characterization method

Abstract

The invention relates to an electric tree real-time observation and ultrahigh frequency partial discharge monitoring combined characterization method, which belongs to the field of packaging insulating material electric tree degradation research, and is used for carrying out real-time observation and recording on electric tree growth in organic silica gel, and carrying out partial discharge signal acquisition and subsequent processing by adopting an ultrahigh frequency probe at the same time. Comprising a high-voltage power supply, a microscopic imaging system and an ultrahigh-frequency partial discharge monitoring system. The method comprises the following steps. The method comprises the following steps: step 1, preparing a needle-plate electrode sample encapsulated by organic silica gel; 2, an electric tree growth platform is built; step 3, adjusting the microscopic imaging system to realize real-time observation of growth of the electrical tree; 4, building an ultrahigh-frequency partial discharge monitoring system; and step 5, characterizing the electrical tree degradation state of the organic silica gel through the combination of electrical tree real-time image detection and a PRPD image.

Description

Technical Field

[0001] The invention belongs to the research field of electrical tree degradation of packaging insulating materials, and particularly relates to a joint characterization method of real-time observation of electrical trees and ultra-high frequency partial discharge monitoring. Background Art

[0002] Silicone gel is often used as a packaging material for power modules due to its good electrical, thermal and mechanical properties, and is used to build insulation systems. Silicone gel wraps the metal electrodes of the substrate with different potentials. During manufacturing, the surface is not smooth enough due to process reasons, and burrs will appear. At the same time, defects such as gaps will be introduced during the module production process. These physical defects will cause the growth and propagation of electrical dendrites in the silicone gel when subjected to electrical and thermal stresses, and eventually breakdown and cause the insulation structure to fail, seriously threatening the service life of the power module. Failure of the insulation system caused by electrical tree growth in silicone gel is a common failure form of power modules. Therefore, a defect simulation sample in the power module was prepared, and an electrical tree growth platform was built to observe the electrical tree growth process in the silicone gel in real time, and partial discharge monitoring was carried out at the same time, and joint characterization was achieved. The above methods will provide a relevant basis for the study of electrical tree degradation in power modules. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for jointly characterizing electrical tree growth by real-time observation and ultra-high frequency partial discharge monitoring, which can realize the joint characterization of electrical tree degradation of package insulation by the growth process of electrical tree and partial discharge characteristics.

[0004] The present invention provides a method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring, comprising:

[0005] Step 1: Prepare a needle-plate electrode sample encapsulated with silicone gel: take two-component addition-type silicone gel A and B components in a mass ratio of 1:1 and place them in a beaker, stir them thoroughly and degas them, encapsulate them in a cavity containing a needle-plate electrode, and then cure them to prepare a sample;

[0006] Step 2: Build an electrical dendrite growth platform: connect the needle electrode and plate electrode of the sample to the high-voltage power supply and the ground wire respectively, and connect the needle electrode to the digital oscilloscope through a high-voltage probe;

[0007] Step 3: Adjust the microscopic imaging system to achieve real-time observation of electrical dendrite growth: adjust the distance between the lens and the sample, select the appropriate magnification and light source intensity, and make the needle tip area clearly visible in the picture;

[0008] Step 4: Build a UHF partial discharge monitoring system: Connect the UHF sensor to the digital oscilloscope and the signal processing system, collect partial discharge signals through the UHF sensor, and further analyze them by the signal processing system;

[0009] Step 5: Characterize the degradation state of silicone gel electrical treeing by combining real-time image detection of electrical treeing with PRPD diagram.

[0010] Furthermore, in step 1, the organic silicon gel is subjected to degassing treatment after mechanical stirring and pouring into the mold, which greatly eliminates the influence of bubbles introduced during stirring and potting on the degradation of electrical treeing of the sample;

[0011] Furthermore, in step 1, the distance between the needle electrode and the plate electrode is set to 3 mm;

[0012] Furthermore, in step 2, the high voltage power supply is a high frequency voltage source, the voltage output is 0 to 50 kV, and the frequency range is 0 to 30 kHz, which can simulate the actual high frequency working condition;

[0013] Furthermore, in step 2, the high voltage power supply is connected to the needle electrode via a protective resistor;

[0014] Furthermore, the microscopic observation system in step 3 can be connected to a display to perform real-time observation and continuous recording to record the initiation and growth process of the electrical tree;

[0015] Furthermore, in step 4, the UHF sensor has a measurement frequency band of 200 MHz to 2 GHz and a sensitivity of 1 pC; the maximum sampling rate of the digital oscilloscope is 10 Gs / s and the sampling bandwidth can reach 1.5 GHz;

[0016] Furthermore, the signal processing in step 4 adopts the sym8 wavelet method to perform wavelet decomposition on the UHF sensor signal;

[0017] Furthermore, in step 5, the electrical tree growth process is linked to the partial discharge characteristics to characterize the degradation state of the electrical tree of the sample; wherein the partial discharge characteristics should include the relationship between the discharge amount, the number of discharges and the phase, which is presented through the PRPD diagram;

[0018] Furthermore, in step 5, the electrical tree growth process is divided into four stages: electrical tree no growth, electrical tree potential, electrical tree development, and electrical tree breakdown;

[0019] Furthermore, the PRPD diagram obtained in step 5 shows that partial discharge mainly occurs at the zero-crossing point and peak value of the voltage.

[0020] Furthermore, in the step 5, there is no obvious discharge signal in the stage where the electrical tree is not growing; there is an obvious local discharge signal in the latent stage of the electrical tree, but there is no electrical tree growth; the local discharge signal is strong in the development stage of the electrical tree, and the growth of the electrical tree is obvious; the local discharge is intense in the breakdown stage of the electrical tree, and the electrical tree grows from the needle electrode to the plate electrode and then breaks down.

[0021] The present invention has at least the following beneficial effects:

[0022] The high-frequency and high-voltage source is used to meet the actual working conditions of power devices, and the needle-plate electrode defect simulates the spike defect of silicone gel encapsulation insulation very well. At the same time, the sample has good transparency, which can realize the real-time recording of the growth process of electrical trees. The partial discharge characteristics obtained by the UHF partial discharge monitoring system are used to characterize the degradation process of electrical trees in silicone gel, which provides a basis for improving the reliability of power device encapsulation insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 The present invention provides a silicone gel-encapsulated needle-plate electrode sample.

[0025] Figure 2 The invention provides a real-time observation platform for electrical tree branches and a UHF partial discharge monitoring platform.

[0026] Figure 3 It is a flow chart of the combined characterization method of organic silicon gel electrical tree degradation and ultra-high frequency partial discharge monitoring provided by the present invention. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those of ordinary skill in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0028] like Figure 1 As shown, the present invention provides a silicone gel-encapsulated needle-plate electrode sample, which at least comprises the following steps:

[0029] Step 1-1: 30 g of each of the silicone gel A and B components are selected and poured into a beaker, and the solution is stirred by mechanical stirring for 15 minutes until the mixture is evenly mixed, and then the mixture is moved to a vacuum chamber for vacuum degassing for 10 minutes to obtain a bubble-free mixture;

[0030] Step 1-2: Assemble the needle electrode and the plate electrode in an acrylic mold. The needle tip needs to be polished before assembly. The distance between the needle tip and the plate electrode is 3 mm.

[0031] Step 1-3: Pour the degassed mixture into the mold until it covers the upper surface of the plate electrode, then move it into a vacuum chamber for degassing for 10 minutes. After the bubbles are eliminated, move the sample into a constant temperature vacuum box and cure it at 60°C for 12 hours to obtain the sample.

[0032] Figure 2 The present invention provides a real-time observation and ultra-high frequency partial discharge monitoring platform for electrical tree branches, which at least includes the following steps:

[0033] Step 2-1: Connect the sample needle electrode to the high-voltage power supply through a protective resistor, and connect the plate electrode to the ground wire; at the same time, connect the input end of the high-voltage probe to the needle electrode, and the output end to the oscilloscope;

[0034] Step 2-2: Place the sample under the microscope observation system, adjust the distance, magnification and light source intensity, so that the needle electrode and plate electrode are clearly visible on the observation screen;

[0035] Step 2-3: Place the UHF sensor at a suitable location next to the sample, connect the digital oscilloscope, connect the oscilloscope to the signal processing system, and store the data obtained by the UHF sensor for subsequent analysis.

[0036] Figure 3 Flow chart of the joint characterization method for silicone gel electrical treeing degradation and UHF partial discharge monitoring.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring, characterized in that: include: Step 1: Prepare a needle-plate electrode sample encapsulated with silicone gel: take two-component addition-type silicone gel A and B components in a mass ratio of 1:1 and place them in a beaker, stir them thoroughly and degas them, encapsulate them in a cavity containing a needle-plate electrode, and then cure them to prepare a sample; Step 2: Build an electrical dendrite growth platform: connect the needle electrode and plate electrode of the sample to the high-voltage power supply and the ground wire respectively, and connect the needle electrode to the digital oscilloscope through a high-voltage probe; Step 3: Adjust the microscope imaging system to achieve real-time observation of electrical dendrite growth: adjust the distance between the lens and the sample, select the appropriate magnification and light intensity, and make the needle tip area clearly visible in the picture. Step 4: Build a UHF partial discharge monitoring system: Connect the UHF sensor to the digital oscilloscope and the signal processing system, collect partial discharge signals through the UHF sensor, and further analyze them by the signal processing system; Step 5: Characterize the degradation state of silicone gel electrical treeing by combining real-time image detection of electrical treeing with PRPD diagram.

2. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1 is characterized in that: In the step 1, the organic silicon gel is degassed after mechanical stirring and pouring into the mold, which greatly eliminates the influence of bubbles introduced during stirring and potting on the degradation of electrical treeing of the sample.

3. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1 is characterized in that: The distance between the needle electrode and the plate electrode in step 1 is set to 3 mm.

4. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1 is characterized in that: In step 2, the high voltage power supply is a high frequency voltage source, the voltage output is 0-50 kV, and the frequency range is 0-30 kHz, which can simulate the actual high frequency working condition.

5. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1 is characterized in that: In step 2, the high voltage power supply is connected to the needle electrode via a protective resistor.

6. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1, characterized in that: In step 3, the microscopic observation system can be connected to a display to perform real-time observation and continuous recording to record the initiation and growth process of the electrical tree.

7. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1 is characterized in that: In step 4, the UHF sensor has a measurement frequency band of 200 MHz to 2 GHz and a sensitivity of 1 pC; the maximum sampling rate of the digital oscilloscope is 10 Gs / s and the sampling bandwidth can reach 1.5 GHz.

8. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1, characterized in that: The signal processing in step 4 adopts the sym8 wavelet method to perform wavelet decomposition on the UHF sensor signal.

9. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1, characterized in that: In step 5, the electrical tree growth process is linked to the partial discharge characteristics to characterize the degradation state of the electrical tree of the sample; wherein the partial discharge characteristics should include the relationship between the discharge amount, the number of discharges and the phase, which is presented through the PRPD diagram.

10. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1, characterized in that: In step 5, the electrical tree growth process is divided into four stages: electrical tree no growth, electrical tree potential, electrical tree development, and electrical tree breakdown.

11. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1, characterized in that: The PRPD diagram obtained in step 5 shows that partial discharge mainly occurs at the zero-crossing point and peak of the voltage.

12. The method for joint characterization of real-time observation of electrical tree branches and ultra-high frequency partial discharge monitoring according to claim 1, characterized in that: In the step 5, there is no obvious discharge signal in the stage where the electrical tree does not grow; there is an obvious local discharge signal in the latent stage of the electrical tree, but there is no electrical tree growth; the local discharge signal is strong in the development stage of the electrical tree, and the growth of the electrical tree is obvious; the local discharge is intense in the breakdown stage of the electrical tree, and the electrical tree grows from the needle electrode to the plate electrode and breaks down.

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