Cable accessory insulation interface discharge state diagnosis method based on escaped gas analysis

Abstract

The invention belongs to the technical field of cable diagnosis, and discloses a cable accessory insulation interface discharge state diagnosis method based on escape gas analysis, which comprises the following steps: analyzing cable accessory insulation interface escape gas characteristics under different discharge types, and determining a cable accessory insulation interface discharge type diagnosis standard; the discharge types comprise interface partial discharge, interface intermittent arc discharge and interface disruptive discharge; collecting and analyzing escaped gas of the insulation interface of the to-be-detected cable accessory; and according to the cable accessory insulation interface discharge type diagnosis standard, determining the insulation interface discharge state of the to-be-tested cable accessory. According to the invention, accurate diagnosis of the insulation interface discharge type can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of cable diagnosis, and in particular relates to a method for diagnosing the discharge state of the insulation interface of a cable accessory based on escaping gas analysis. Background Art

[0002] Power cables are the main veins of urban power transmission. Cable accessories, as key components of the electrical connection of the cable system, are the weak link of the cable system. Both operating experience and research results show that most cable accessory failures are related to insulation interface discharge. As the operating time increases, the discharge gradually develops until the interface completely loses its insulation performance and eventually causes the cable accessory breakdown failure. Accurately detecting the insulation interface discharge of cable accessories is of great significance to ensure the safe and reliable operation of the cable system.

[0003] The insulation status detection technology of cable accessories can be generally divided into electrical measurement methods and non-electrical measurement methods. Commonly used methods include partial discharge method, temperature measurement method, etc. Field operation experience shows that these methods generally have problems such as susceptibility to interference, low sensitivity and poor reliability, resulting in a low detection rate of cable accessory defects and difficulty in timely detection of early faults such as insulation interface discharge. Current research has found that gas will be generated during the development of defects such as cable overheating and discharge. The type and concentration of gas products are strongly correlated with the type and degree of defects and are not easily interfered with. Therefore, by analyzing the characteristics of the generated gas, it is expected to achieve effective identification of cable accessory defects and accurate assessment of insulation status.

[0004] At present, the research on cable gas generation mainly focuses on the cable body, while the insulation structure and materials of cable accessories are completely different from those of the cable body, and the defect types are quite different from those of the cable body. Cable accessories mainly use elastomeric insulation materials such as silicone rubber (SiR), which are fitted with the cable body XLPE insulation to form an interface insulation structure. Due to the difference in the elemental composition and structural units of SiR and the cable body materials, the gas generation characteristics of the insulation interface should be significantly different from those of the cable body. In addition, when there are impurities such as air gap cavities and moisture inside the insulation interface, these impurities will cause partial discharge under the action of the electric field. During long-term operation, partial discharge may evolve into intermittent arc discharge, and eventually cause permanent breakdown failure of the insulation interface. The development process of interface discharge shows obvious stages, and the types and characteristics of discharge in each stage are different. There are obvious differences in the characteristics of gas products under the action of different interface discharge types. Existing research on cable gas diagnosis mainly focuses on gas generation due to defects in the cable body, while the gas generation characteristics under the action of insulation interface discharge of cable accessories are not clear. Exploring the characteristics of gas escaping from the insulation interface of cable accessories under different discharge types can lay a theoretical foundation for the insulation status diagnosis method of cable accessories based on gas analysis. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for diagnosing the insulation interface discharge state of cable accessories based on escaping gas analysis, so as to achieve accurate diagnosis of the insulation interface discharge type.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions to achieve it.

[0007] The present invention provides a method for diagnosing the discharge state of the insulation interface of a cable accessory based on the analysis of the escaped gas, which comprises the following steps:

[0008] S1 analyzes the characteristics of gas released from the insulation interface of cable accessories under different discharge types, and determines the diagnostic criteria for the discharge types of the insulation interface of cable accessories; the discharge types include partial discharge at the interface, intermittent arc discharge at the interface, and breakdown discharge at the interface;

[0009] S2 collects the escaping gas from the insulation interface of the cable accessories to be tested and analyzes it;

[0010] S3 determines the insulation interface discharge state of the cable accessory to be tested according to the cable accessory insulation interface discharge type diagnosis standard.

[0011] In the above step S1, a cable accessory insulation interface discharge experimental platform is built, and then experiments of different discharge types are carried out, and the characteristics of the gas escaping from the insulation interface during the experiment are analyzed to determine the diagnosis standard of the cable accessory insulation interface discharge type.

[0012] The cable accessory insulation interface discharge experimental platform includes a non-partial discharge test device, an insulation interface unit gas production device and a signal acquisition system; the non-partial discharge test device includes a transformer, a protective resistor, a voltage divider and a voltage regulator; the voltage regulator, the transformer and the protective resistor are connected in sequence; the voltage divider is connected in series with the branch where the protective resistor and the transformer are located, and the voltage divider is connected in parallel with the insulation interface unit gas production device, and the signal output end of the voltage divider is connected to the recorder of the signal acquisition system; the insulation interface unit gas production device includes a sealed cavity for installing an insulation interface sample and a gas collection unit deep into the sealed cavity; the insulation interface sample is composed of an XLPE sample and a SiR sample in interface contact, and a needle electrode and a plate electrode are placed between the XLPE sample and the SiR sample; the needle electrode is connected to the input end of the voltage divider through a wire, the voltage signal is measured through the voltage divider, and the recorder is connected; the plate electrode is grounded, the current signal on the grounding line is measured through a high-frequency current sensor, and the recorder is connected; the recorder sends the collected voltage and current data to a host computer connected to it.

[0013] The structure of the insulating interface sample is as follows: the insulating interface sample is composed of an XLPE sample and a SiR sample stacked together; the needle and plate electrodes are placed between the SiR sample and the XLPE sample, the interface pressure is applied by a bolt group and a spring, and the insulating interface sample is fixed in a sealed cavity by a fixing unit. The fixing unit includes an organic glass plate, a stud, a nut and a spring, the stud and the nut form a bolt group, the insulating interface sample is placed between the upper and lower organic glass plates, and is fixed by a stud and a nut passing through the organic glass plate, and a spring is provided between the organic glass plate and the nut.

[0014] In the above step S1, the following steps are performed using the above cable accessories insulation interface discharge test platform:

[0015] (1) conducting discharge experiments of different discharge types respectively and collecting the gas released from the insulation interface; the discharge types include interface partial discharge, interface intermittent arc discharge and interface breakdown discharge;

[0016] (2) The gas content of the escaped gas collected from the discharge experiments of different discharge types is analyzed by gas chromatography; the diagnostic standard of the discharge type of the insulation interface of the cable accessories is obtained through analysis:

[0017] (i) For interfacial partial discharge, the small molecule gases produced include CO2, H2, CO, and CH4;

[0018] (ii) For intermittent arc discharge at the interface, the small molecule gases produced include CO2, H2, CO, C2H4, C2H2, CH4, and C2H6;

[0019] (iii) For interface breakdown discharge, the small molecule gases produced include H2, CO2, C2H2, CO, C2H4, CH4, and C2H6.

[0020] Furthermore, during the interface local discharge gas production experiment, voltage was applied to the interface sample until local discharge occurred, the interface gas escaping under the local discharge condition was collected, and the gas composition and content were analyzed; during the interface intermittent discharge gas production experiment, voltage was applied to the interface sample until intermittent arc discharge occurred, the interface gas escaping under the intermittent arc discharge condition was collected, and the gas composition and content were analyzed; during the interface breakdown gas production experiment, voltage was applied to the interface sample until continuous arc discharge occurred, and the same voltage was continued to be applied until the interface broke down, the interface gas escaping under the interface breakdown condition was collected, and the gas composition and content were analyzed.

[0021] Furthermore, in (i), for the interfacial partial discharge, the relationship between the content of small molecule gases produced is CO2>H2≈CO>CH4;

[0022] In (ii), for intermittent arc discharge at the interface, the relationship between the content of small molecule gases produced is CO2>H2>CO≈C2H4≈C2H2>CH4>C2H6;

[0023] In (iii), for the interface breakdown discharge, the relationship between the content of small molecule gases produced is H2>CO2>C2H2>CO>C2H4>CH4>C2H6.

[0024] Further, in the above (ii), the content of unsaturated hydrocarbons is C2H4:C2H2≈1;

[0025] In the above (iii), the content of unsaturated hydrocarbons is C2H4:C2H2≈0.6.

[0026] The above step S1 also includes:

[0027] (3) The volatile organic compounds in the escaped gas collected from the discharge experiments of different discharge types were analyzed by gas chromatography-mass spectrometry; the diagnostic criteria for the discharge type of the insulation interface of cable accessories were also obtained through analysis:

[0028] (iv) For interfacial partial discharge, no volatile organic compounds were detected;

[0029] The volatile organic compounds detected by interfacial intermittent arc discharge and interface breakdown discharge include several main types of VOC (Volatile Organic Compounds), such as organic oxides, silicon-containing organic compounds, olefins, alkynes, alkanes, aromatic hydrocarbons, and nitrogen-containing organic compounds.

[0030] Furthermore, in (iv), for interfacial intermittent arc discharge, the relationship between the volatile organic matter content is: olefins > organic oxides > alkynes ≈ silicon-containing organic matter > alkanes > aromatic hydrocarbons > nitrogen-containing organic matter;

[0031] For interfacial breakdown discharge, the relationship between the volatile organic matter content is: olefins > alkynes > organic oxides > silicon-containing organic matter ≈ aromatic hydrocarbons > nitrogen-containing organic matter > alkanes.

[0032] In the above (iv), the silicon-containing organic compound includes hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane.

[0033] In the above step S2, the collected escaped gas is analyzed by a gas chromatograph and / or a gas chromatograph-gas spectrometer.

[0034] Compared with the prior art, the cable accessories insulation interface discharge state diagnosis method based on escaping gas analysis provided by the present invention has the following beneficial effects:

[0035] 1) The present invention builds a cable accessory insulation interface discharge experimental platform, studies the characteristics of escaping gas under different discharge types, and determines the diagnostic standard of the cable accessory insulation interface discharge type;

[0036] 2) The present invention has found through research that, for partial discharge at the interface, only small molecules of H2, CO2, CO, and CH4 are produced; for intermittent arc discharge and interface breakdown, small molecules of H2, CO2, CO, CH4, C2H6, C2H4, and C2H2 are produced; the ratio of C2H2 content to C2H4 content in the escaping gas of interface breakdown is higher than that of intermittent arc discharge at the interface; based on this, the diagnosis of discharge types such as partial discharge at the interface, intermittent discharge, and interface breakdown can be realized;

[0037] 3) The present invention has also been found through research that, for partial discharge at the interface, no volatile organic compounds are generated, and the gases released during intermittent discharge at the interface and breakdown at the interface contain several types of VOCs, such as organic oxides, silicon-containing organic compounds, olefins, alkynes, alkanes, aromatic hydrocarbons, and nitrogen-containing organic compounds; the total discharge at the interface breakdown is the highest, and the proportion of alkynes is higher; the interface breakdown consumes a large amount of oxygen, which makes the proportion of organic oxides higher; the pyrolysis reaction becomes more intense after the oxygen is consumed, which makes the proportion of aromatic hydrocarbons higher;

[0038] 4) The present invention has also found through research that there are silicon-containing organic substances in the escaping gases caused by intermittent arc discharge at the interface and breakdown at the interface, wherein the main components are hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic flow chart of a method for diagnosing the discharge state of the insulation interface of cable accessories based on escaping gas analysis provided in an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of the structure of a cable accessory insulation interface discharge test platform provided by an embodiment of the present invention;

[0041] Figure 3 It is a schematic diagram of the structure of the gas production device of the insulation interface unit;

[0042] Figure 4 This is a schematic diagram of an interface sample in an embodiment of the present invention;

[0043] Figure 5 The gas chromatography analysis results of the gas production experiment of the interface sample in the embodiment of the present invention;

[0044] Figure 6 is the percentage of different types of VOC content in the gas production experiment of the interface sample in the embodiment of the present invention;

[0045] Figure 7is the ratio of VOC gas released by different discharge types in the gas production experiment of the interface sample in the embodiment of the present invention;

[0046] In the figure, 1-non-partial discharge test device, 11-transformer, 12-protective resistor, 13-voltage divider, 14-voltage regulator, 2-insulating interface unit gas production device, 21-sealed chamber, 22-gas collecting unit, 22-1-gas guide tube, 22-2-syringe, 22-3-gas valve, 23-fixing unit, 23-1-plexiglass plate, 23-2-stud, 23-3-nut, 23-4-spring, 3-signal acquisition system; 31-wave recorder. DETAILED DESCRIPTION

[0047] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0048] Example

[0049] like Figure 1 As shown, an embodiment of the present invention provides a method for diagnosing the discharge state of the insulation interface of a cable accessory based on the analysis of the escaped gas, which comprises the following steps:

[0050] S1 analyzes the characteristics of gas released from the insulation interface of cable accessories under different discharge types, and determines the diagnostic criteria for the discharge types of the insulation interface of cable accessories; the discharge types include partial discharge at the interface, intermittent arc discharge at the interface, and breakdown discharge at the interface;

[0051] S2 collects the escaping gas from the insulation interface of the cable accessories to be tested and analyzes it;

[0052] S3 determines the insulation interface discharge state of the cable accessory to be tested according to the cable accessory insulation interface discharge type diagnosis standard.

[0053] The above steps S1-S3 are explained in detail below in conjunction with specific experiments.

[0054] In the above step S1, a cable accessory insulation interface discharge experimental platform is built, and then experiments of different discharge types are carried out, and the characteristics of the gas escaping from the insulation interface during the experiment are analyzed to determine the diagnosis standard of the cable accessory insulation interface discharge type.

[0055] The insulating interface samples used in this embodiment are prepared from XLPE samples and SiR samples. The XLPE samples in the interface samples are pressed from XLPE pellets into samples with a size of 50mm×25mm×2mm, and the surface is evenly polished with 400-mesh sandpaper. The SiR samples are purchased samples with a size of 20mm×20mm×2mm made by vulcanizing SiR raw rubber. After the sample preparation is completed, the surfaces of XLPE and SiR are wiped with alcohol, rinsed with distilled water, placed in a vacuum drying oven at 70°C for 24 hours, and then taken out for use.

[0056] The cable accessories insulation interface discharge test platform used in this embodiment is as follows: Figure 2-Figure 3 As shown, it includes a non-partial discharge test device 1, an insulating interface unit gas production device 2 and a signal acquisition system 3.

[0057] The non-partial discharge test device 1 is used to apply voltage to the insulation interface sample. The non-partial discharge test device 1 includes a transformer 11, a protective resistor 12, a voltage divider 13 and a voltage regulator 14; the voltage regulator 14, the transformer 11, and the protective resistor 12 are connected in sequence; the voltage divider 13 is connected in series to the branch where the protective resistor 12 and the transformer 11 are located, and the voltage divider 13 is connected in parallel with the insulation interface unit gas production device 2, and the signal output end of the voltage divider 13 is connected to the recorder 31 of the signal acquisition system 3.

[0058] The insulating interface unit gas production device 2 includes a sealed cavity 21 for installing an insulating interface sample and a gas collection unit 22 extending deep into the sealed cavity 21. The insulating interface sample is fixed in the sealed cavity by a fixing unit 23. The fixing unit 23 includes an organic glass plate 23-1, a stud 23-2, a nut 23-3 and a spring 23-4. The stud 23-2 and the nut 23-3 form a bolt group. The insulating interface sample is placed between the upper and lower organic glass plates 23-1 and fixed by the stud 23-2 and the nut 23-3 passing through the organic glass plate 23-1. A spring 23-4 is provided between the organic glass plate 21 and the nut. The assembled fixing unit 23 can also be fixed in the sealed cavity 21 by a bracket. The gas collection unit 22 includes an air guide tube 22-1 extending deep into the sealed cavity 21 and a syringe 22-2 connected to the air guide tube 22-1. The syringe 22-2 is used to collect gas; an air valve 22-3 is provided on the air guide tube 22-1.

[0059] The insulating interface sample includes XLPE samples and SiR samples stacked together, and the needle electrode and plate electrode are placed between the SiR sample and the XLPE sample. The interface pressure is applied by the bolt group and the spring to make the interface in close contact. The plate electrode size is 40mm×20mm, the needle electrode is 40mm long, 10mm wide, the needle tip angle is 40°, and the vertical distance between the needle and plate electrodes is 5mm. The needle electrode 23 is connected to the input end of the voltage divider 13 through a wire, and the voltage signal is measured through the voltage divider and connected to the recorder. The plate electrode is grounded, and the current signal on the ground line is measured through a wire through a high-frequency current sensor and connected to the recorder 31; the recorder 31 sends the collected voltage and current data to the host computer 32 connected to it.

[0060] In the above step S1, the following steps are performed using the above cable accessories insulation interface discharge test platform:

[0061] (1) Discharge experiments of different discharge types were carried out and the gas released from the insulating interface was collected; the discharge types included interface partial discharge, interface intermittent arc discharge and interface breakdown discharge.

[0062] During the interface partial discharge gas generation experiment, a stable partial discharge occurred when a voltage of 5.6 kV was applied to the interface sample. After 48 hours of pressurization, the escaping gas was collected by the gas collection unit. Based on the collected partial discharge current waveform, according to the formula The average discharge capacity within 48 hours of pressurization is calculated to be about 1.6×10 -8 C. There is no obvious change between the interface partial discharge sample and the interface sample before the experiment, such as Figure 4 shown.

[0063] During the intermittent arc discharge gas generation experiment, intermittent arc discharge occurred when 6.7 kV voltage was applied to the interface sample. When continuous discharge occurred, the pressure was stopped and the escaped gas was collected by the gas collection unit. Intermittent arc discharge usually occurred near the voltage peak and lasted for 1 / 4 cycle or 1-4 cycles before extinguishing. The average discharge amount was about 1.1×10 -4 C. Compared with the interface samples before the experiment, the interface samples after intermittent discharge showed a small and uniformly distributed shallow depression between the two electrodes on the surface of the XLPE and SiR samples, and there were light gray ablation channels and a small amount of carbon black particles on the surface of the material, such as Figure 4 shown.

[0064] During the interface breakdown gas generation experiment, a continuous and stable arc discharge phenomenon occurred when a voltage of 7.5 kV was applied to the interface sample. The voltage of 7.5 kV was continued to be applied until the interface was broken down. The average discharge amount was about 2.5×10 -2C, and then the escaping gas is collected by the gas collection unit. After the breakdown, the interface samples, XLPE and SiR samples have obvious deep groove type electric track channels on the surface, and a large range of shallow depressions appear around the deep groove type electric track; there are a large number of white particles in the SiR electric track channel, and there are obvious ablation marks and a large number of carbon black particles between the interfaces, such as Figure 4 shown.

[0065] (2) The gas content of the escaped gas collected from the discharge experiments of different discharge types was analyzed by gas chromatography.

[0066] In order to reduce the impact of experimental randomness, three groups of repeated tests were carried out on gas generation by partial discharge at the interface, gas generation by intermittent arc discharge at the interface, and gas generation by breakdown at the interface. The contents of seven small molecule gases, H2, CO2, CO, CH4, C2H6, C2H4, and C2H2, in the escaping gas were analyzed using a gas chromatograph. The gas chromatographic results are shown in Figure 2. Figure 5 shown.

[0067] According to the results of gas chromatography analysis, the content relationship of small molecule gases produced by partial discharge at the interface is CO2>H2≈CO>CH4, and no C2H6, C2H4, or C2H2 gases are produced. The content relationship of small molecule gases produced by intermittent arc discharge at the interface is CO2>H2>CO≈C2H4≈C2H2>CH4>C2H6, and unsaturated hydrocarbon gases are produced, and the content of unsaturated hydrocarbons is C2H4:C2H2≈1. The content relationship of small molecule gases produced by interface breakdown is H2>CO2>C2H2>CO>C2H4>CH4>C2H6, and the content of unsaturated hydrocarbons is C2H4:C2H2≈0.6, and the unsaturation of small molecule hydrocarbon gases increases.

[0068] The diagnostic criteria for the discharge type of the insulation interface of cable accessories are obtained through analysis:

[0069] (i) For interfacial partial discharge, the small molecule gases generated include CO2, H2, CO, and CH4; the content of the small molecule gases generated is in the relationship of CO2>H2≈CO>CH4;

[0070] (ii) For intermittent arc discharge at the interface, the small molecule gases generated include CO2, H2, CO, C2H4, C2H2, CH4, and C2H6; the content of the small molecule gases generated is in the following relationship: CO2>H2>CO≈C2H4≈C2H2>CH4>C2H6, and C2H4:C2H2≈1;

[0071] (iii) For interface breakdown discharge, the small molecule gases generated include H2, CO2, C2H2, CO, C2H4, CH4, and C2H6. The content relationship of the small molecule gases generated is H2>CO2>C2H2>CO>C2H4>CH4>C2H6, and C2H4:C2H2≈0.6.

[0072] (3) The volatile organic compounds in the escaping gases collected from discharge experiments of different discharge types were analyzed by gas chromatography-mass spectrometry.

[0073] The gas released from three groups of interface partial discharge gas generation experiments, interface intermittent arc discharge gas generation experiments and interface breakdown gas generation experiments were analyzed by gas chromatography-mass spectrometry. No VOC was detected in the gas released from interface partial discharge, and some gas chromatography-mass spectrometry experimental results of gas released from interface intermittent arc discharge and interface breakdown are shown in Table 1.

[0074] Table 1 Results of gas generation by discharge gas chromatography-mass spectrometry of interface unit samples

[0075]

[0076]

[0077] VOCs with a credibility of more than 70 in the GC-MS results were screened out and divided into several main VOC types according to the different functional groups, including organic oxides, silicon-containing organics, olefins, alkynes, alkanes, aromatic hydrocarbons, nitrogen-containing organics, etc. The percentage of each VOC content is as follows: Figure 6 shown.

[0078] According to the results of gas chromatography-mass spectrometry, the VOC content of intermittent arcing gas is: olefins> organic oxides> alkynes ≈ silicon-containing organic matter> alkanes> aromatic hydrocarbons> nitrogen-containing organic matter, and the VOC content of interfacial breakdown gas is: olefins> alkynes> organic oxides> silicon-containing organic matter ≈ aromatic hydrocarbons> nitrogen-containing organic matter> alkanes. The percentage of olefin content in intermittent arcing and interface breakdown gas is the highest, the percentage of olefin and alkane content in intermittent arcing gas is higher, and the percentage of other VOC content in interface breakdown gas is higher.

[0079] Through analysis, it is concluded that the diagnostic standards for the discharge type of the insulation interface of cable accessories also include:

[0080] (iv) For interfacial partial discharge, no volatile organic compounds were detected;

[0081] The volatile organic compounds detected by interfacial intermittent arc discharge and interface breakdown discharge include several main types of VOC (Volatile Organic Compounds), such as organic oxides, silicon-containing organic compounds, olefins, alkynes, alkanes, aromatic hydrocarbons, and nitrogen-containing organic compounds.

[0082] Furthermore, in (iv), for interfacial intermittent arc discharge, the relationship between the volatile organic matter content is: olefins > organic oxides > alkynes ≈ silicon-containing organic matter > alkanes > aromatic hydrocarbons > nitrogen-containing organic matter;

[0083] For interfacial breakdown discharge, the relationship of volatile organic matter content is: olefins > alkynes > organic oxides > silicon-containing organics ≈ aromatic hydrocarbons > nitrogen-containing organics > alkanes;

[0084] Silicon-containing organic compounds include hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane.

[0085] As a semi-quantitative method, the ratio of the peak areas of two substances in the same test can represent the ratio of the content of the two substances. The ratio of some VOCs can reflect the development trend of various chemical reactions, such as Figure 7 shown.

[0086] C in the gas released from intermittent arc discharge at the interface 烷烃 / C 不饱和烃 Greater than C in the gas released by interface breakdown 烷烃 / C 不饱和烃 , and the C in the gas released by intermittent arc discharge at the interface 炔烃 / C 烯烃 Less than C in the gas released by interface breakdown 炔烃 / C 烯烃 As the average discharge amount increases, the proportion of alkane content decreases; the proportion of alkyne content increases, and the unsaturation degree of hydrocarbon VOC increases. 有机氧化物 / C 不饱和烃 Less than C in the gas released by interface breakdown 有机氧化物 / C 不饱和烃 , indicating that the proportion of oxide content increases with the increase of average discharge capacity. The oxidation reaction is more likely to occur under aerobic conditions. As the average discharge capacity increases, more alkyl radicals and activated oxygen are produced, making the self-oxidation reaction more intense. 芳香烃 / C C3 -4 不饱和烃 Less than C in the gas released by interface breakdown 芳香烃 / C C3 -4 不饱和烃 , indicating that with the increase of the average discharge amount, short-chain unsaturated hydrocarbons are cyclized into aromatic hydrocarbons. There is a small amount of oxygen between the interfaces. During the long-term arcing process that eventually leads to interface breakdown, the oxygen content gradually decreases, the temperature rises, and the alkyl radicals undergo a thermal decomposition reaction similar to incomplete combustion. In addition, the surface of the sample with interface breakdown contains a large amount of carbon black particles and soot particles produced by combustion. C含硅有机物 / C 不饱和烃 Greater than C in the gas released by interface breakdown 含硅有机物 / C不饱和烃 , indicating that the proportion of unsaturated hydrocarbon content increases with the increase of average discharge amount. On the one hand, compared with SiR, XLPE main chain bond energy is lower and more prone to decomposition. On the other hand, at higher energy, SiR methyl side chain is prone to homolytic cleavage reaction, and the generated methyl radicals may rearrange to produce alkyl radicals with more carbon atoms, thereby generating more unsaturated hydrocarbons.

[0087] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0088] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0089] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0090] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0091] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for diagnosing the discharge state of the insulation interface of cable accessories based on escaping gas analysis, characterized in that: The following steps are involved: S1 analyzes the characteristics of gas released from the insulation interface of cable accessories under different discharge types, and determines the diagnostic criteria for the discharge types of the insulation interface of cable accessories; the discharge types include partial discharge at the interface, intermittent arc discharge at the interface, and breakdown discharge at the interface; S2 collects the escaping gas from the insulation interface of the cable accessories to be tested and analyzes it; S3 determines the insulation interface discharge state of the cable accessory to be tested according to the cable accessory insulation interface discharge type diagnosis standard.

2. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to claim 1 is characterized in that: In step S1, a cable accessory insulation interface discharge experimental platform is built, and then experiments of different discharge types are carried out, and the characteristics of the gas escaping from the insulation interface during the experiment are analyzed to determine the diagnostic standard of the cable accessory insulation interface discharge type; the cable accessory insulation interface discharge experimental platform is used to perform the following steps: (1) Conduct discharge experiments of different discharge types and collect the gas escaping from the insulating interface; (2) The gas content of the escaped gas collected from the discharge experiments of different discharge types is analyzed by gas chromatography; the diagnostic standard of the discharge type of the insulation interface of the cable accessories is obtained through analysis: (i) For interfacial partial discharge, the small molecule gases produced include CO2, H2, CO, and CH4; (ii) For intermittent arc discharge at the interface, the small molecule gases produced include CO2, H2, CO, C2H4, C2H2, CH4, and C2H6; (iii) For interface breakdown discharge, the small molecule gases produced include H2, CO2, C2H2, CO, C2H4, CH4, and C2H6.

3. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to claim 2 is characterized in that: The cable accessory insulation interface discharge experimental platform includes a non-partial discharge test device, an insulation interface unit gas production device and a signal acquisition system; the non-partial discharge test device includes a transformer, a protective resistor, a voltage divider and a voltage regulator; the voltage regulator, the transformer and the protective resistor are connected in sequence; the voltage divider is connected in series with the branch where the protective resistor and the transformer are located, and the voltage divider is connected in parallel with the insulation interface unit gas production device, and the signal output end of the voltage divider is connected to the recorder of the signal acquisition system; the insulation interface unit gas production device includes a sealed cavity for installing an insulation interface sample and a gas collection unit deep into the sealed cavity; the insulation interface sample is composed of an XLPE sample and a SiR sample in interface contact, and a needle electrode and a plate electrode are placed between the XLPE sample and the SiR sample; the needle electrode is connected to the input end of the voltage divider through a wire, the voltage signal is measured through the voltage divider, and the recorder is connected; the plate electrode is grounded, the current signal on the grounding line is measured through a high-frequency current sensor, and the recorder is connected; the recorder sends the collected voltage and current data to a host computer connected to it.

4. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to claim 3 is characterized in that: The insulating interface sample is composed of an XLPE sample sheet and a SiR sample sheet stacked together, and the insulating interface sample is fixed in the sealed cavity by a fixing unit.

5. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to claim 2 is characterized in that: In (i), for interfacial partial discharge, the relationship between the content of small molecule gases produced is CO2>H2≈CO>CH4; In (ii), for intermittent arc discharge at the interface, the relationship between the content of small molecule gases produced is CO2>H2>CO≈C2H4≈C2H2>CH4>C2H6; In (iii), for the interface breakdown discharge, the relationship between the content of small molecule gases produced is H2>CO2>C2H2>CO>C2H4>CH4>C2H6.

6. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to claim 2 is characterized in that: Step S1 also includes: (3) The volatile organic compounds in the escaped gas collected from the discharge experiments of different discharge types were analyzed by gas chromatography-mass spectrometry; the diagnostic criteria for the discharge type of the insulation interface of cable accessories were also obtained through analysis: (iv) For interfacial partial discharge, no volatile organic compounds were detected; The volatile organic compounds detected for interfacial intermittent arc discharge and interfacial breakdown discharge include the main VOC types of organic oxides, silicon-containing organics, olefins, alkynes, alkanes, aromatic hydrocarbons, and nitrogen-containing organics.

7. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to claim 6 is characterized in that: (iv), for interfacial intermittent arc discharge, the relationship of volatile organic matter content is: olefins > organic oxides > alkynes ≈ silicon-containing organics > alkanes > aromatic hydrocarbons > nitrogen-containing organics; For interfacial breakdown discharge, the relationship between the volatile organic matter content is: olefins > alkynes > organic oxides > silicon-containing organic matter ≈ aromatic hydrocarbons > nitrogen-containing organic matter > alkanes.

8. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to claim 7 is characterized in that: In (iv), the silicon-containing organic compound includes hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane.

9. The method for diagnosing the discharge state of the insulation interface of cable accessories based on the analysis of the escaped gas according to any one of claims 1 to 8, characterized in that: In step S2, the collected escaped gas is analyzed by a gas chromatograph and / or a gas chromatograph-gas spectrometer.

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