CN115308490A - Method capable of simultaneously measuring interface traps and interface resistivity of multilayer solid medium - Google Patents

Method capable of simultaneously measuring interface traps and interface resistivity of multilayer solid medium Download PDF

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CN115308490A
CN115308490A CN202210942902.1A CN202210942902A CN115308490A CN 115308490 A CN115308490 A CN 115308490A CN 202210942902 A CN202210942902 A CN 202210942902A CN 115308490 A CN115308490 A CN 115308490A
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interface
sample
electrode
resistivity
interface sample
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吴凯
冯玉
吴少雷
骆晨
张云霄
张天峰
戚振彪
董苏
赵成
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Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/045—Circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
    • G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
    • G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation

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Abstract

The invention provides a method for simultaneously measuring the interface trap and the interface resistivity of a multilayer solid medium, which comprises the following steps: step S1: preparing an XLPE/SIR interface sample with a specified thickness; placing a test electrode and a high-voltage electrode in the middle of the interface sample; wherein the high-voltage electrode is connected with a direct-current high voltage, and the test electrode is connected with the skin ampere meter; step S2: firstly, connecting an interface sample into a high-voltage power supply in a test circuit for polarization, then carrying out liquid nitrogen cooling on the interface sample to a first specified temperature value, and at the moment, grounding and short-circuiting the interface sample; and step S3: completing the polarization and depolarization of the interface sample; and step S4: obtaining the thermal stimulation current value of the interface sample and the recorded interface sample temperature value under the thermal stimulation current; s5, acquiring a TSC curve; and S6, acquiring the interface trap and the interface resistivity of the interface sample according to the TSC curve. The invention has good effect.

Description

Method capable of simultaneously measuring interface traps and interface resistivity of multilayer solid medium
Technical Field
The invention belongs to the technical field of solid medium material parameter testing, and particularly relates to a method capable of simultaneously measuring a multilayer solid medium interface trap and interface resistivity.
Background
In recent years, nearly 20% of cabling has been in operation for more than 20 years, and it is expected that, in the next 10 years, early commissioning cabling will continue to enter the end of the expected economic life. In the long-term operation process, the cable is subjected to the combined aging effect of electricity, heat and force, and the faults of the distribution network cable are obviously increased. The multilayer composite medium interface of the cable joint is used as the weakest place of a cable system, the influence factors of insulation failure of the interface under the combined aging effect are extremely complex, and in addition, the rule is not clear due to the limitation of a measuring means and a representation method, so that the time for stable operation of the cable system is greatly limited. Past data have shown that the cable joint composite media interface is the weakest point in the overall cable system. More and more scholars are focusing on the study of composite interfaces. Researches show that under the coupling action of multiple physical fields such as high voltage, high electric field, high temperature field and the like, the cable is gradually aged, molecular chains of the crosslinked polyethylene and the silicone rubber are broken, microscopic defects are continuously enlarged, and the defects can capture carriers to form space charges. The electric field inside the material can be distorted as space charge accumulates, further exacerbating the aging of the material. Therefore, the research on the composite interface is deeply carried out, so that reasonable characterization technology and method are provided, the correlation between the interface charge trap and the interface charge behavior is cleaned, and the method has important significance for promoting the research on the aging of the insulating material.
In recent years, many students use high-precision optical instruments such as a transmission electron microscope, a raman spectroscopy and a dynamic mechanical analyzer to research the microscopic interface of the composite material, however, the method can only be used for researching the appearance of the microscopic interface, and the charge characteristic and the trap characteristic of the interface are difficult to be reflected visually. Researchers have also studied the aging of insulating materials by using Pulse Electroacoustic (PEA), isothermal current attenuation (IEC), frequency domain dielectric spectroscopy (FDS), and the like. The methods have some defects, wherein the pulse electroacoustic method and the frequency domain dielectric spectroscopy can not directly obtain the trap level which is an important parameter for describing the material performance through calculation, and the isothermal current attenuation method has long testing time and can not distinguish a plurality of polarization processes, so that the polarization mechanism is difficult to describe. Meanwhile, it can be found that the current measurement technology focuses more on the study of the charge characteristics of single-layer cross-linked polyethylene, and the study method and characterization technology for the double-layer composite medium interface or multi-layer solid medium interface trap and the interface resistivity of the cross-linked polyethylene and the silicone rubber are still insufficient.
Therefore, it is necessary to design a method for simultaneously measuring the interface trap and the interface resistivity of the multilayer solid medium to solve the above technical problems.
Disclosure of Invention
In order to solve the problems, the invention provides a method for simultaneously measuring the interface trap and the interface resistivity of a multilayer solid medium, which comprises the following steps:
step S1: preparing an XLPE/SIR interface sample with a specified thickness; placing a test electrode and a high-voltage electrode in the middle of the interface sample; wherein the high-voltage electrode is connected with a direct-current high voltage, and the test electrode is connected with the skin ampere meter;
step S2: firstly, connecting an interface sample into a high-voltage power supply in a test circuit for polarization, then carrying out liquid nitrogen cooling on the interface sample to a first specified temperature value, and at the moment, grounding and short-circuiting the interface sample;
and step S3: removing the depolarization electric field at the designated time, linearly heating to a second designated temperature value at a designated rate, and completing the polarization and depolarization of the interface sample;
and step S4: according to the linear temperature rise process, obtaining the thermal stimulation current value of the interface sample and the recorded interface sample temperature value under the thermal stimulation current through a picoammeter;
s5, acquiring a TSC curve according to the thermal stimulation current value and the interface sample temperature value;
and S6, acquiring an interface trap and interface resistivity of the interface sample according to the TSC curve.
Further, the area between the high-voltage electrode and the test electrode is a test interface area.
Furthermore, protective electrodes are respectively arranged on the upper surface and the lower surface of the interface sample.
Further, a protective resistor in the test circuit is used for preventing the surface safety meter from being damaged when the interface sample is subjected to breakdown or flashover along the surface.
Further, in the process of linear temperature rise, the short-circuit current of the test circuit is the thermal stimulation current.
The invention provides a method for simultaneously measuring the interface trap and the interface resistivity of a multilayer solid medium, and the measurement circuit device can realize the measurement of the polarization and depolarization process and the interface resistivity of a sample only by controlling a switch.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 shows a cross-sectional isometric view of a four-electrode system according to an embodiment of the invention.
Fig. 2 shows a longitudinal section elevation of a four-electrode system according to an embodiment of the invention.
Fig. 3 shows a flow chart for measuring solid media interface traps and interface resistivity in accordance with an embodiment of the invention.
FIG. 4 shows a schematic diagram of a measurement circuit according to an embodiment of the invention.
Fig. 5 shows a schematic diagram of controlling a temperature controller to inject liquid nitrogen to the periphery of a sample for cooling according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the present invention provides a method for simultaneously measuring the interface trap and the interface resistivity of a multilayer solid medium, the method comprising:
step S1: preparing an XLPE (cross-linked polyethylene)/SIR (surface insulation resistance) interface sample (the interface sample is of a double-layer structure and comprises an XLPE sample and an SIR sample) with a specified thickness; placing a test electrode and a high-voltage electrode in the middle of the interface sample; the high-voltage electrode is connected with direct-current high voltage, the testing electrode is connected with the skin ampere meter, the area between the high-voltage electrode and the testing electrode is a testing interface area, and in addition, protective electrodes are respectively arranged on the upper surface and the lower surface of the interface sample;
step S2: firstly, an interface sample is connected to a high-voltage power supply in a test circuit for polarization, wherein a protective resistor in the test circuit is used for preventing a skin ampere meter from being damaged when the interface sample is punctured or flashover along a surface, then the interface sample is cooled to a first specified temperature value by liquid nitrogen, and at the moment, the interface sample is grounded and short-circuited;
and step S3: removing the depolarization electric field at the designated time, linearly heating to a second designated temperature value at a designated rate, and completing the polarization and depolarization of the interface sample;
and step S4: according to the method, the thermal stimulation current value of the interface sample and the recorded interface sample temperature value under the thermal stimulation current (the interface sample temperature value can be obtained through a temperature controller) are obtained through a picoammeter in the linear temperature rising process, wherein the short-circuit current of a test circuit is the thermal stimulation current in the linear temperature rising process, and the thermal stimulation current method can intuitively reflect the trap characteristic of the composite material interface so as to judge the insulating property of the insulating material;
s5, acquiring a TSC curve (the TSC curve is formed by the thermal stimulation current and the corresponding temperature value) according to the thermal stimulation current value and the interface sample temperature value;
s6, acquiring an interface trap and interface resistivity of the interface sample according to the TSC curve;
the step S6 specifically includes:
after the TSC curve is obtained, the TSC curve can be analyzed, so that the temperature corresponding to the current peak value and the half peak value of the interface sample is obtained, and the material interface trap level and the trapped charge quantity can be obtained by utilizing a formula;
the interfacial resistivity is related to the interfacial resistance, the electrode length and the electrode spacing, as can be seen from the interfacial resistivity formula. And measuring the length of the electrodes of the annular four-electrode system and the distance between the electrodes, and calculating to obtain the interface resistivity of the composite material according to ohm's law by utilizing the current readings displayed by the picoampere meter.
The following description will be made with reference to an embodiment.
As shown in fig. 1-5, wherein fig. 1 and 2 are a cross-sectional isometric view and a longitudinal elevation view, respectively, of an annular four-electrode system (i.e., the annular four-electrode device of fig. 3) for measuring XLPE/SIR interfacial resistivity. The system comprises units I to seven, wherein the unit I is that a test electrode 1 is connected with a measuring unit (namely a picoammeter); the second unit is a high-voltage electrode 2 connected with a high-voltage power supply, wherein the area between the first unit and the second unit is a fifth test interface area unit, and the fifth unit is an annular copper electrode sprayed by a vacuum ion sputtering instrument; the third and fourth units are respectively a protective electrode 3 and a protective electrode 4; unit six is an SIR sample; unit seven is an XLPE sample, specifically:
the unit comprises a third unit, a sixth unit, a seventh unit and a fourth unit from top to bottom in sequence, wherein the upper end of the second unit is arranged in the inner hole of the sixth unit, the lower end of the second unit is arranged in the inner hole of the seventh unit, the second unit is annular, the fifth unit is arranged in the inner hole of the second unit, and the first unit is arranged in the inner hole of the fifth unit.
Fig. 3 is a flowchart of the present invention, which includes the following specific steps:
an annular four-electrode device was prepared as shown in fig. 1. Respectively measuring the radius r of the high voltage electrode 1 1 And the ring width r of the interface test area unit five 2 . The test electrode and the high-voltage electrode are arranged in the interface sample, and in order to reduce the air gap of the composite interface, the test electrode and the high-voltage electrode are made as thin as possible; and meanwhile, protective electrodes are respectively arranged on the upper surface of the third unit and the lower surface of the fourth unit, and the current flowing from the high-voltage electrode 2 to the testing electrode 1 is composed of the bulk current of part of the interface sample, so that the calculated interface resistivity value is smaller than the actual value. After the protective electrodes 3 and 4 are arranged, more body current in the interface sample flows to the protective electrodes, so that the effect of shielding leakage current in the interface sample is achieved. In addition, a certain pressure needs to be applied to the whole interface sample device to reduce the gap between the layers;
as shown in fig. 4, the test circuit includes a temperature controller, a computer, a high voltage power supply, a pico-ampere meter, a protection resistor, a switch S1, a switch S2, a heater, and two heat-preservation packs, wherein the heat-preservation packs cover the whole annular four-electrode system, the heat-preservation packs are placed in a liquid nitrogen pool, and the two heaters are respectively placed on the upper surface of the protection electrode 3 and the lower surface of the protection electrode 4.
Close switch S1, openAnd (2) opening the S2, connecting the interface sample into a high-voltage power supply (when the switch S1 is closed and the S2 is disconnected, the high-voltage electrode 2 is connected with the positive electrode of the high-voltage power supply, the negative electrode of the high-voltage power supply is not connected with the protective electrode 3, the wire is led out from the test electrode 1 to be connected with the Pian ammeter, and then the wire is connected into the negative electrode of the high-voltage power supply through the protective resistor) so as to be polarized for a period of time. Then, liquid nitrogen is injected into the heat preservation bag unit at the periphery of the interface sample through a temperature controller to be rapidly cooled as shown in figure 5, and the temperature of the interface sample is reduced to T 0 At this point, the charge inside the interface sample is considered to have been "frozen". At the moment, the switch S1 is opened, the switch S2 is closed, the interface sample is grounded and short-circuited for a period of time, and the influence of surface charges of the interface sample is eliminated;
the output of the DC power supply is controlled to a certain value by the temperature controller, so that the heater linearly heats the interface sample to T at a certain speed beta 1 ；
The output value of the direct current power supply is continuously adjusted through the temperature controller, and then the heating power of the heater is adjusted. The method comprises the steps that a skin ampere meter obtains a short-circuit current of an external circuit, namely a thermal stimulation current of an interface sample, a computer is used for obtaining a temperature value corresponding to the current value in real time, data are drawn into a TSC curve, S1 and S2 are closed, and the interface sample is cooled to normal temperature, so that the interface resistivity can be measured;
obtaining temperature values corresponding to the peak current and the half-peak current according to the TSC curve, and calculating trap parameters of a material interface, including a trap level E and a trapped charge quantity Q:
Figure BDA0003786460850000061
Figure BDA0003786460850000062
wherein K is Boltzmann's constant; tm is the temperature corresponding to the current peak value; delta T is a temperature difference value corresponding to a current half-peak value; t is a unit of 0 And T 1 Respectively as a temperature rise stage t 0 And t 1 Is correspondingly provided withThe temperature value of (a); i (T) is the TSC current; beta is the speed K/min corresponding to the linear temperature rise stage; i (t) represents the TSC current as a function of time.
By using an annular four-electrode system, according to a calculation formula of the interface resistivity:
Figure BDA0003786460850000063
where rho if Is the interfacial resistivity, R if The interface resistance of the interface sample is given as l is the electrode length and g is the electrode spacing. The interfacial resistivity of the interfacial sample can be calculated according to equation (3):
Figure BDA0003786460850000064
in the formula of U O Is a direct current high voltage power supply; I.C. A 0 Is the number of the Pian table; r is the resistance value of the protection resistor; l. the 0 I.e. the length (2 r) of the high voltage electrode 1 +r 2 )π；g 0 Namely the ring width r of a ring electrode (ring copper electrode sprayed by a vacuum ion sputtering apparatus) in an interface test area 2 Wherein r is 1 Is the radius of the high voltage electrode 1, r 2 The ring width of the ring-shaped copper electrode for sputtering by a vacuum ion sputtering apparatus.
The invention also has the following advantages:
1. only one measuring circuit device (the measuring circuit device is shown in figure 4, namely, the parts except the annular four-electrode system in figure 4 are all parts of the measuring circuit device) is required to be built, so that the multilayer solid medium interface trap and the interface resistivity can be obtained, and the measuring device is simple and convenient;
2. the invention is suitable for high-voltage measurement, and can be suitable for external application of more than 10 KV;
3. the parameters obtained by the method are strictly calculated through a formula, are more intuitive and have higher accuracy
4. On one hand, the invention provides a new measuring means and technology for the characterization of the composite insulating material interface, for example, the technical means is only suitable for the measurement of an XLPE/SIR double-layer solid medium interface trap and interface resistivity, and is also suitable for the measurement of the interface trap and the interface resistivity of other single-layer or multi-layer polymer materials; on the other hand, a solid foundation is laid for the design of the insulating material of the high-voltage equipment, the research of aging and the evaluation of the service life.
Although the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present invention.

Claims (5)

1. A method for simultaneously measuring the interface trap and the interface resistivity of a multilayer solid medium is characterized by comprising the following steps:
step S1: preparing an XLPE/SIR interface sample with a specified thickness; placing a test electrode and a high-voltage electrode in the middle of the interface sample; wherein the high-voltage electrode is connected with direct-current high voltage, and the testing electrode is connected with the skin ampere meter;
step S2: firstly, connecting an interface sample into a high-voltage power supply in a test circuit for polarization, then carrying out liquid nitrogen cooling on the interface sample to a first specified temperature value, and at the moment, grounding and short-circuiting the interface sample;
and step S3: removing the depolarization electric field at the designated time, linearly heating to a second designated temperature value at a designated rate, and completing the polarization and depolarization of the interface sample;
and step S4: according to the linear temperature rise process, obtaining the thermal stimulation current value of the interface sample and the recorded interface sample temperature value under the thermal stimulation current through a picoammeter;
s5, acquiring a TSC curve according to the thermal stimulation current value and the interface sample temperature value;
and S6, acquiring the interface trap and the interface resistivity of the interface sample according to the TSC curve.
2. The method for simultaneously measuring the interface trap and the interface resistivity of the multilayer solid medium as claimed in claim 1, wherein the region between the high voltage electrode and the test electrode is a test interface region.
3. The method for simultaneously measuring the interface trap and the interface resistivity of the multilayer solid medium according to claim 2, wherein the upper surface and the lower surface of the interface sample are respectively provided with a protective electrode.
4. The method as claimed in claim 3, wherein the protection resistor in the test circuit is used to prevent the Pian meter from being damaged when the interface sample is broken down or flashover along the surface.
5. The method for simultaneously measuring the interface trap and the interface resistivity of the multilayer solid medium according to claim 4, wherein in the process of linear temperature rise, the short-circuit current of the test circuit is the thermal stimulation current.
CN202210942902.1A 2022-08-08 2022-08-08 Method capable of simultaneously measuring interface traps and interface resistivity of multilayer solid medium Pending CN115308490A (en)

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