Non-uniform electric field semi-conductive material charge testing device

Abstract

The utility model belongs to the technical field of charge testing, and provides a non-uniform electric field semi-conductive material charge testing device, which comprises a signal generator, a pulse matching circuit, a high-voltage direct-current power supply, a charge testing platform, a signal acquisition module and an oscilloscope, the charge test platform comprises a metal cavity, a metal electrode, a semiconductive upper spherical electrode, a crosslinked polyethylene slice material and a lower electrode; the metal electrode, the semiconductive upper spherical electrode, the crosslinked polyethylene slice material and the lower electrode are sequentially attached and coaxially arranged in the metal cavity from top to bottom; the signal generator is connected with the pulse matching circuit, the pulse matching circuit and the high-voltage direct-current power supply are coupled to generate a direct-current test pulse signal, and the direct-current test pulse signal acts on the crosslinked polyethylene slice material sequentially through the metal electrode and the semiconductive upper spherical electrode; and the signal acquisition module is connected with the lower electrode and is used for acquiring an ultrasonic signal generated by space charges in the crosslinked polyethylene slice material, converting the ultrasonic signal into an electric signal, amplifying the electric signal and transmitting the electric signal to an oscilloscope.

Description

Technical Field

[0001] The utility model belongs to the technical field of charge testing, and in particular relates to a semi-conductive material charge testing device in a non-uniform electric field. Background Art

[0002] The statements in this section merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] With the rapid development of high-voltage direct current (HVDC) cables, research has focused on the material selection of the outer semiconductive shielding layer. The primary locations for power cable failures are the cable itself and cable accessories. Cross-linked polyethylene (XLPE) is the mainstream insulation material for HVDC cables, but there are multiple material options for the outer semiconductive shielding layer. The semiconductive material in the cable itself is mostly made of ethylene-vinyl acetate copolymer (EVA) and carbon black (CB). However, the semiconductive material in cable accessories, such as the stress cone, is currently mostly made of two rubber materials: silicone rubber (SR) or ethylene propylene diene monomer (EPDM) and carbon black (CB). Research has found that different base semiconductive materials exhibit significant differences in conductivity and physical and mechanical properties. These differences can inhibit charge injection into the semiconductive material to varying degrees. Furthermore, a comparison of the transient evolution of space charge at the interface of an insulation discontinuity under DC voltages of different polarities reveals a significant polarity effect on charge accumulation at the discontinuous interface. Wedge-shaped electrodes distort the electric field strength, exacerbating charge accumulation and leading to partial discharge.

[0004] The electrodes of existing semi-conductive material charge testing devices mostly adopt the needle-plate electrode form, which is only suitable for testing the charge distribution characteristics under extremely non-uniform electric fields, and is not suitable for testing the charge distribution characteristics under slightly non-uniform electric fields. In addition, the main parts of power cable failure are the cable body and cable accessories. Cross-linked polyethylene is the mainstream material for the insulation layer of high-voltage DC cables, but there is more than one material choice for the semi-conductive shielding layer on the outside of the cable. Different base semi-conductive materials have significant differences in conductivity and physical and mechanical properties. These differences will have varying degrees of inhibitory effects on the injection of charge into the semi-conductive material. Existing charge testing devices are mostly dielectric materials and do not consider the impact of semi-conductive materials on the charge accumulation of cross-linked polyethylene slice materials, thereby affecting the accuracy of charge test results. Utility Model Content

[0005] In order to solve the technical problems existing in the above background technology, the utility model provides a semi-conductive material charge testing device in a non-uniform electric field, which can improve the insulation performance of cross-linked polyethylene slice materials and enhance the accuracy of charge test results.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A device for testing the charge of a semi-conductive material in a non-uniform electric field, comprising: a signal generator, a pulse matching circuit, a high-voltage DC power supply, a charge testing platform, a signal acquisition module, and an oscilloscope;

[0008] The charge test platform includes a metal cavity and a metal electrode, a semi-conductive upper spherical electrode, a cross-linked polyethylene slice material and a lower electrode; the metal electrode, the semi-conductive upper spherical electrode, the cross-linked polyethylene slice material and the lower electrode are sequentially and coaxially arranged in the metal cavity from top to bottom;

[0009] The signal generator is connected to a pulse matching circuit, and the pulse matching circuit is coupled with a high-voltage DC power supply to generate a DC test pulse signal, which acts on the cross-linked polyethylene slice material through the metal electrode and the semi-conductive upper spherical electrode in turn; the signal acquisition module is connected to the lower electrode, and is used to collect the ultrasonic signal generated by the space charge in the cross-linked polyethylene slice material, convert it into an electrical signal, and transmit it to the oscilloscope after amplification.

[0010] As an implementation mode, silicone oil is provided on the upper side of the lower electrode in the metal cavity.

[0011] As an embodiment, the depth of the silicone oil is higher than the upper surface of the cross-linked polyethylene slice material and lower than the upper surface of the semi-conductive upper spherical electrode.

[0012] As an embodiment, the signal acquisition module includes a connected piezoelectric sensor and a signal amplifier; the piezoelectric sensor is attached to the lower surface of the lower electrode.

[0013] As an embodiment, the piezoelectric sensor is a PVDF piezoelectric film sensor.

[0014] As an embodiment, the size of the cross-linked polyethylene chip material is larger than the size of the semi-conductive upper spherical electrode.

[0015] As an embodiment, the pulse matching circuit includes an isolation filtering module, a zero-crossing comparison module and a pulse converter, the input end of the isolation filtering module is connected to the signal generator, the output end of the isolation filtering module is connected to the input end of the zero-crossing comparison module, and the output end of the zero-crossing comparison module is connected to the pulse converter.

[0016] In one embodiment, the lower electrode is grounded.

[0017] As an embodiment, the diameter of the semi-conductive upper spherical electrode is 15 mm.

[0018] As an embodiment, the metal cavity is provided with two cable holes, and a first cable and a second cable are respectively passed through the two cable holes, one end of the first cable and the second cable are connected to the metal electrode, the other end of the first cable is connected to the pulse matching circuit, and the other end of the second cable is connected to the high-voltage DC power supply.

[0019] The beneficial effects of the utility model are:

[0020] The electrodes of the semi-conductive material charge testing device in a non-uniform electric field of the utility model adopt a semi-conductive upper spherical electrode and a lower electrode to form a ball-plate electrode model. The average electric field strength is maintained constant by adjusting the amplitude of the DC polarization voltage applied to the semi-conductive upper spherical electrode. The starting time of applying the polarization voltage is set as the zero time. By selecting different times, the internal space charge movement characteristics of the medium in the instantaneous non-uniform electric field can be obtained.

[0021] The utility model applies a DC test pulse to the cross-linked polyethylene slice material of the charge test platform through a pulse matching circuit and a high-voltage DC power supply, and adopts semi-conductive upper spherical electrodes with different substrates to respectively perform charge tests on the cross-linked polyethylene slice material, thereby obtaining different test charge distribution data for comparison, and realizing the test collection of the spatial charge distribution of the cross-linked polyethylene slice material under DC high field strength.

[0022] During the charge test process, the utility model uses silicone oil to effectively isolate the current, prevent current leakage or arc transmission, improve the insulation performance of the cross-linked polyethylene slice material, improve the accuracy of the charge test results, and provide a data basis for studying the spatial charge accumulation of insulating materials of semi-conductive materials under high DC field strength.

[0023] Advantages of additional aspects of the present invention will be partially given in the following description, and partially become apparent from the following description, or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention.

[0025] Figure 1 It is a structural schematic diagram of a semi-conductive material charge testing device in a non-uniform electric field according to an embodiment of the present utility model.

[0026] In the picture:

[0027] 1. Metal cavity; 2. Metal electrode; 3. Semi-conductive upper spherical electrode; 4. Lower electrode; 5. Cross-linked polyethylene slice material; 6. Piezoelectric sensor; 7. Signal amplifier; 8. Silicone oil. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0031] Cross-linked polyethylene (XLPE) insulated cables are widely used in power transmission and distribution systems due to their excellent properties, such as high dielectric strength, low dielectric loss, good heat and aging resistance, and easy construction and installation. However, the dielectric strength of cables degrades during operation due to electrical aging and thermal stress. This gradual degradation caused by the combined stress on the dielectric is closely related to the reliability of electrical equipment, making the safe operation of cables a key factor in the stability of power systems.

[0032] When a dielectric is subjected to electrical stress, space charge (charge stored in a localized location) is generated in the insulator or on its surface, significantly affecting the insulation performance. Existing research shows that the negative impact of space charge characteristics under DC conditions on dielectrics is due to the local field enhancement caused by the continuous accumulation of charges of a given polarity. The amount of space charge under DC stress is positively correlated with the aging time, so it can also represent a characteristic indicator of the degree of aging. The accumulation of space charge accelerates the electrical aging of the insulating material, thereby reducing its service life. The breakdown of the insulating medium occurs after the space charge accumulates to a certain threshold, which seriously damages the insulation system and threatens the reliable operation of cable accessories.

[0033] Figure 1 This is a schematic diagram of the structure of the semi-conductive material charge test device in a non-uniform electric field according to an embodiment of the present invention. Figure 1 As shown, a device for testing the charge of a semi-conductive material in a non-uniform electric field of this embodiment includes: a signal generator, a pulse matching circuit, a high-voltage DC power supply, a charge testing platform, a signal acquisition module, and an oscilloscope;

[0034] The charge test platform includes a metal cavity 1 and a metal electrode 2 (such as a copper electrode), a semi-conductive upper spherical electrode 3, a cross-linked polyethylene chip material 5 and a lower electrode 4; the metal electrode 2, the semi-conductive upper spherical electrode 3, the cross-linked polyethylene chip material 5 and the lower electrode 4 are coaxially arranged in the metal cavity 1 from top to bottom.

[0035] The signal generator is connected to a pulse matching circuit, which is coupled with a high-voltage DC power supply to generate a DC test pulse signal. This signal is then applied to the cross-linked polyethylene slice material 5 via the metal electrode 2 and the semi-conductive upper spherical electrode 3. The signal acquisition module is connected to the lower electrode 4 and is used to collect ultrasonic signals generated by space charge in the cross-linked polyethylene slice material 5, convert them into electrical signals, amplify them, and transmit them to an oscilloscope. In this embodiment, the lower electrode 4 is grounded.

[0036] In the specific implementation process, silicone oil 8 is provided on the upper side of the lower electrode 4 in the metal cavity 1. The depth of the silicone oil 8 is higher than the upper surface of the cross-linked polyethylene slice material 5 and lower than the upper surface of the semi-conductive upper spherical electrode 3.

[0037] In this embodiment, the signal acquisition module includes a connected piezoelectric sensor 6 and a signal amplifier 7; the piezoelectric sensor 6 is attached to the lower surface of the lower electrode 4. The piezoelectric sensor 6 is a PVDF piezoelectric film sensor. The piezoelectric sensor 6 can convert the collected ultrasonic signal into an electrical signal and transmit it to the signal amplifier 7 for signal amplification.

[0038] In a specific embodiment, the device for testing the charge of a semiconductive material in a non-uniform electric field of the embodiment can be provided with a semiconductive upper spherical electrode 3 of various carbon black (CB) doping materials. For example, the semiconductive upper spherical electrode 3 can be an ethylene-vinyl acetate copolymer (EVA) semiconductive upper spherical electrode 3, a silicone rubber (SR) semiconductive upper spherical electrode 3, and an ethylene propylene diene monomer (EPDM) semiconductive upper spherical electrode 3. The diameter of the semiconductive upper spherical electrode 3 is 15 mm. The size of the cross-linked polyethylene chip material 5 is larger than that of the semiconductive upper spherical electrode 3.

[0039] Specifically, the pulse matching circuit includes an isolation filtering module, a zero-crossing comparison module and a pulse converter. The input end of the isolation filtering module is connected to the signal generator, the output end of the isolation filtering module is connected to the input end of the zero-crossing comparison module, and the output end of the zero-crossing comparison module is connected to the pulse converter.

[0040] Specifically, the signal generator can generate a sinusoidal wave signal of a specific frequency and amplitude. The input end of the isolation filter module is connected to the signal generator. The isolation filter module can collect the sinusoidal wave signal of the signal generator, isolate and reduce noise, and filter out noise interference; the output end of the isolation filter module is connected to the input end of the zero-crossing comparison module. The zero-crossing comparison module can convert the sinusoidal wave signal into a square wave voltage signal with equal period. The output end of the zero-crossing comparison module is connected to a pulse converter. The pulse converter can synchronize the received square wave voltage signal into a pulse signal.

[0041] It should be noted that the isolation filter module, the zero-crossing comparison module and the pulse converter can all be implemented using existing circuit structures, which will not be described in detail here.

[0042] In this embodiment, the metal cavity 1 is provided with two cable holes, and a first cable and a second cable are respectively passed through the two cable holes. One end of the first cable and the second cable are connected to the metal electrode 2, the other end of the first cable is connected to the pulse matching circuit, and the other end of the second cable is connected to the high-voltage DC power supply.

[0043] In this embodiment, the charge test platform is respectively connected to a pulse matching circuit and a high-voltage DC power supply. The pulse matching circuit is coupled to the metal electrode 2 of the charge test platform through a series capacitor through the top opening of the charge test platform and the high-voltage DC power supply through a series resistor through the side opening of the charge test platform. The charge test platform generates a DC test pulse by receiving a pulse signal and a high-voltage current. The DC test pulse is injected by the metal electrode 2 and acts on the cross-linked polyethylene chip material 5 below through the semi-conductive upper spherical electrode 3. The space charge in the cross-linked polyethylene chip material 5 generates an ultrasonic signal through the vibration of the pulsed DC battery. The ultrasonic signal is collected by a signal acquisition module and generates an electrical signal. The signal acquisition module is connected to an oscilloscope, which can receive the electrical signal of the signal acquisition module. At the same time, the oscilloscope is also connected to a computer terminal and can upload the stored signal waveform to the computer terminal to obtain the final charge test waveform.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A device for testing the charge of a semiconducting material in a non-uniform electric field, characterized in that: include: Signal generator, pulse matching circuit, high-voltage DC power supply, charge test platform, signal acquisition module and oscilloscope; The charge test platform includes a metal cavity and a metal electrode, a semi-conductive upper spherical electrode, a cross-linked polyethylene slice material and a lower electrode; the metal electrode, the semi-conductive upper spherical electrode, the cross-linked polyethylene slice material and the lower electrode are sequentially and coaxially arranged in the metal cavity from top to bottom; The signal generator is connected to a pulse matching circuit, and the pulse matching circuit is coupled with a high-voltage DC power supply to generate a DC test pulse signal, which acts on the cross-linked polyethylene slice material through the metal electrode and the semi-conductive upper spherical electrode in turn; the signal acquisition module is connected to the lower electrode, and is used to collect the ultrasonic signal generated by the space charge in the cross-linked polyethylene slice material, convert it into an electrical signal, and transmit it to the oscilloscope after amplification.

2. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 1, wherein: Silicone oil is provided in the metal cavity on the upper side of the lower electrode.

3. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 2, wherein: The depth of the silicone oil is higher than the upper surface of the cross-linked polyethylene slice material and lower than the upper surface of the semi-conductive upper spherical electrode.

4. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 1, wherein: The signal acquisition module includes a connected piezoelectric sensor and a signal amplifier; the piezoelectric sensor is attached to the lower surface of the lower electrode.

5. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 4, wherein: The piezoelectric sensor is a PVDF piezoelectric film sensor.

6. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 1, wherein: The size of the cross-linked polyethylene slice material is larger than that of the semi-conductive upper spherical electrode.

7. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 1, wherein: The pulse matching circuit includes an isolation filter module, a zero-crossing comparison module and a pulse converter. The input end of the isolation filter module is connected to the signal generator, the output end of the isolation filter module is connected to the input end of the zero-crossing comparison module, and the output end of the zero-crossing comparison module is connected to the pulse converter.

8. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 1, wherein: The lower electrode is grounded.

9. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 1, wherein: The diameter of the semi-conductive upper spherical electrode is 15 mm.

10. The device for testing the charge of a semiconductive material in a non-uniform electric field according to claim 1, wherein: The metal cavity is provided with two cable holes, into which a first cable and a second cable are respectively passed, one end of each of the first cable and the second cable is connected to a metal electrode, the other end of the first cable is connected to a pulse matching circuit, and the other end of the second cable is connected to a high-voltage DC power supply.

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