Monitoring system for VOCS of transformer substation cable trench

Abstract

The invention discloses a transformer substation cable trench VOCS monitoring system, comprising: an acquisition unit comprising a plurality of sampling joints arranged in a cable trench, a pretreatment gas circuit for converging, filtering and drying the plurality of sampling joints, a direct acquisition branch, an inspection enrichment branch, an on-line enrichment branch, and a conveying gas circuit; the sampling analysis unit comprises a purging gas circuit, a vacuum gas circuit, an atmosphere bypass gas circuit and a collection analysis gas circuit which are connected with the conveying gas circuit through a pipeline, and the submission enrichment branch comprises an adsorption sampling module which can be detached for submission. The on-line enrichment branch comprises an on-line thermal desorption adsorption sampling module and a thermal desorption inspection gas path connected with a thermal desorption interface of the on-line thermal desorption adsorption sampling module, the thermal desorption inspection gas path is connected to a collection and analysis gas path, and the collection and analysis gas path is used for carrying out on-line analysis on VOCS gas from the direct collection branch and the thermal desorption inspection gas path. According to the invention, comprehensive collection and dynamic monitoring of the VOCs with wide boiling point and high and low concentrations in the cable trench are realized.

Description

Technical Field

[0001] The present invention relates to the field of substation fire safety, and in particular to a VOC S monitoring system. Background Art

[0002] The cable trench is an underground pipeline used for laying and replacing power or telecommunication cable facilities. It is also the enclosure structure of the cable laying facilities and an indispensable infrastructure in the substation. Its cables are generally laid in layers and bundles in a relatively concentrated manner.

[0003] Once a cable catches fire, the fire will spread to adjacent cables and even cause a larger area of ​​cables to burn, which will not only cause power outages and threaten the safe and stable operation of the power grid, but may also cause significant property losses and social impacts.

[0004] Volatile organic compounds (VOCs) usually refer to organic compounds with a boiling point below 50℃~260℃ at normal pressure.

[0005] Most of the cables currently in operation use polyethylene, cross-linked polyethylene, polystyrene, polypropylene, natural rubber and other materials as insulation materials. They will gradually age due to long-term operation in high voltage, temperature and humidity seasons, and alternating day and night environments. They will also decompose organic gases accompanied by physical and chemical changes under the influence of many factors such as electric current, electromagnetic fields, and oxidation reactions. If allowed to develop, the overall structure of the sheath will fail, causing electrical fire accidents.

[0006] The periodic inspections of densely laid cables in substations are mostly conventional inspections such as infrared and temperature sensing. There is a lack of effective gas detection methods, and qualitative and quantitative inspection and analysis of volatile organic compounds (VOCs) have not yet been carried out.

[0007] At present, most substations are unmanned, and substations are widely distributed, in remote areas, and far away. There are many cable trenches in each station. If they are tested one by one, it will greatly increase the workload of the staff and affect work efficiency. At the same time, due to the large variety of VOCs in the cable trenches, low concentrations, large temperature and humidity differences between day and night in the outdoor laying area, and significant differences in properties, the commonly used VOCs detection methods are difficult to achieve the purpose of comprehensive sampling of VOCs in the area.

[0008] In summary, it is necessary to design a VOC suitable for substation cable trenches. S monitoring system to implement its internal VOC S Dynamic monitoring / surveillance. Summary of the invention

[0009] The purpose of the present invention is to provide a VOC for substation cable trench SA monitoring system is developed to achieve real-time sampling and monitoring of substation cable trenches.

[0010] To this end, the present invention provides a VOC for substation cable trench S The monitoring system comprises a collection unit for collecting VOCs in a cable trench, a sampling and analysis unit and a control unit, wherein the collection unit comprises a plurality of sampling joints arranged in the cable trench, a pretreatment gas circuit for converging and filtering and drying the plurality of sampling joints, a direct sampling branch, a test enrichment branch, an online enrichment branch, and a delivery gas circuit, wherein the direct sampling branch, the test enrichment branch, and the online enrichment branch are connected in parallel, and the sampling and analysis unit comprises a purge gas circuit, a vacuum gas circuit, and an atmospheric bypass gas circuit connected to the delivery gas circuit pipeline. The purge air path is used to purge the collection unit with nitrogen before the collection test, the vacuum air path is used to vacuum self-clean the collection unit before the collection test, the inspection enrichment branch includes an adsorption sampling module that can be disassembled for inspection, the online enrichment branch includes an online thermal desorption adsorption sampling module and a thermal desorption inspection air path connected to its thermal desorption interface, the thermal desorption inspection air path is connected to the collection and analysis air path, and the collection and analysis air path is used to collect VOCs from the direct collection branch and the online inspection branch. S Gas is analyzed online.

[0011] The present invention aims at the collection and analysis of VOCs in the cable trench of the substation, and proposes a comprehensive collection method for high and low concentration VOCs with a wide boiling point that has low detection cost, high efficiency, and simple operation. It not only ensures the safe operation of the cable line, but also reduces the workload and labor intensity of the inspection and maintenance personnel, which is of great significance for improving the safe operation level of the cable trench.

[0012] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0014] Figure 1 The invention is used for substation cable trench VOC S The schematic diagram of the monitoring system;

[0015] Figure 2 It is a structural schematic diagram of the cable trench of the present invention along the longitudinal section;

[0016] Figure 3 It is a schematic structural diagram of a cross section of a cable trench of the present invention;

[0017] Figure 4 is a schematic structural diagram of the enrichment thermal desorption module of the present invention;

[0018] Figure 5 It is a schematic diagram of the structure of the control unit of the present invention.

[0019] Description of Figure Numbers

[0020] Cable trench 1, cable laying 1-1, cable trench cover 1-2, cable trench fireproof plugging 1-3, cable support 1-4; sampling unit 2, 1~3# combiners 2-1, 2-2, 2-3, 1~7# quick connectors 2-4, 2-5, 2-6, 2-7, 2-8, 2-9, 2-10, 4# combiner 2-11, dust filter 2-12, dryer 2-13, inspection module 2-14, online enrichment module 2-15;

[0021] Groove-type joint 2-151, tongue-type joint 2-152, activated carbon adsorption chamber 2-153, molecular sieve adsorption chamber 2-154, clay adsorption chamber 2-155, metal organic framework material adsorption chamber 2-156, polymer adsorption resin adsorption chamber 2-157, heating coil 2-158, thermal desorption interface 2-159, booster pump 2-16, voltage stabilizer 2-17, condenser 2-18, sampling joint 2-19, sampling pump 3;

[0022] Data acquisition and analysis module 4, data processing and early warning module 5, calibration module 6, nitrogen bottle 7, pressure reducing valve 8; vacuum pump 9; manual two-position three-way valve S1, manual valves V1~V2, electric valves MV1~MV11, vacuum gauge VG. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0024] Combined with reference Figures 1 to 5 The present invention is used for substation cable trench VOC S The monitoring system includes: a collection unit, a sampling and analysis unit and a control unit. The collection unit is used to collect VOCs in the cable trench. It can be disassembled and transported to the laboratory for analytical qualitative and quantitative detection and analysis, and can also be enriched online for qualitative and quantitative detection and analysis by thermal desorption and direct collection of qualitative and quantitative detection and analysis.

[0025] The cable trench 1 is covered with a cable trench cover 1-2, which is divided into sections by fireproof plugging 1-3. This description is a section. Several layers of cable brackets 1-4 are installed on the left and right side walls of the cable trench 1. Each layer of cable brackets 1-4 is equipped with multiple cables 1-1 and sampling connectors 2-19. The number of collection units can be increased according to the actual laying conditions of the substation to achieve VOC inside the cable trench of the entire station. S Dynamic monitoring and surveillance.

[0026] The control unit is electrically connected to the collection unit and the sampling and analysis unit respectively.

[0027] The collection unit includes a gas path system and a sampling connector.

[0028] The gas circuit system includes a pretreatment gas circuit for converging and filtering and drying several sampling joints, a direct sampling branch, an inspection enrichment branch, an online enrichment branch, and a conveying gas circuit. The direct sampling branch, the inspection enrichment branch, and the online enrichment branch are connected in parallel.

[0029] Specifically, the gas circuit system includes 1# to 3# combiners 2-1, 2-2, and 2-3, 1# to 7# quick connectors 2-4, 2-5, 2-6, 2-7, 2-8, 2-9, and 2-10, 4# combiner 2-11, dust filter 2-12, dryer 2-13, inspection module 2-14, online enrichment module 2-15, booster pump 2-16, voltage stabilizer 2-17, condenser 2-18, electric valves MV1 to MV8, and manual valve V1.

[0030] The sampling joint is connected to the pre-treatment gas circuit composed of 1~3# concentrators (i.e. branch concentrators) 2-1, 2-2, 2-3, 1~6# quick connectors 2-4, 2-5, 2-6, 2-7, 2-8, 2-9, electric valves MV1~3, 4# concentrators (i.e. main concentrators) 2-11, 7# quick connectors 2-10, dust filter 2-12, manual two-position three-way valve S1, and dryer 2-13 in sequence through pipelines. The pre-treatment gas circuit is used to filter and dry the dust and moisture in the gas in the cable trench.

[0031] The pretreatment gas circuit is respectively connected to the direct sampling branch, the inspection enrichment branch, and the online enrichment branch. The three branches are connected in parallel and are also connected to the transmission gas circuit.

[0032] The pretreatment gas circuit is connected to the direct-collection and transmission gas circuit composed of the electric valve MV4, the booster pump 2-16, the voltage stabilizer 2-17 and the electric valve MV7 in sequence through pipelines.

[0033] The pretreatment gas circuit is connected in sequence through pipelines to the inspection module (i.e., adsorption sampling module) 2-14, electric valve MV5, online enrichment module 2-15, electric valve MV6, booster pump 2-16, voltage stabilizer 2-17, and electric valve MV7 to form an enrichment and delivery gas circuit (including inspection enrichment and online enrichment).

[0034] The pretreatment gas circuit is connected in sequence through pipelines to the thermal desorption inspection gas circuit composed of electric valve MV5, online enrichment module (ie, online thermal desorption adsorption sampling module) 2-15, electric valve MV6, condenser 2-18, and electric valve MV8.

[0035] Direct gas collection and transmission line is used to collect and analyze high-concentration VOC components in cable trenchesS ; Enriched gas transmission line is used for low concentration complex VOC in cable trench S Qualitative and quantitative analysis to ensure VOC collection S The value is real and effective, providing accurate samples for later laboratory analysis. The thermal desorption gas path is used for low-concentration complex VOC in cable trenches S Online qualitative and quantitative analysis to ensure VOC collection S The value is real and valid.

[0036] There are multiple collection units, which are distinguished according to the fire-proof blocking intervals of the cable trench. This description is a section of fire-proof blocking interval. The number of collection units can be increased according to the actual laying conditions of the substation to realize dynamic monitoring of VOCS inside the cable trench of the entire station.

[0037] The sampling and analysis unit comprises a purge air path, a vacuum air path, an atmospheric bypass air path and a collection and analysis air path which are connected to the conveying air path pipeline.

[0038] The sampling and analysis unit includes a sampling pump 3, a data acquisition and analysis module 4, a data processing and early warning module 5, a calibration module 6, a nitrogen bottle 7, a pressure reducing valve 8, a vacuum pump 9, and electric valves MV9 to MV11.

[0039] The collection unit is connected to the electric valve MV9, sampling pump 3, and data collection and analysis module 4 in sequence through pipelines to collect high-concentration VOC components in the cable trench. S Collect and analyze gas path.

[0040] The collection unit is connected to the purge gas circuit consisting of the electric valve MV10, the pressure reducing valve 8, and the nitrogen bottle 7 in sequence through pipelines. The purge gas circuit is used to purge the gas circuit system to ensure the collection of VOC S The value is real and valid.

[0041] The collection unit is connected to the vacuum air circuit composed of the electric valve MV11, vacuum gauge VG, and vacuum pump 9 in sequence through pipelines. The vacuum air circuit is used to self-clean the air circuit system and regenerate the adsorption materials of the inspection module and the online enrichment module in combination with the purge air circuit to ensure VOC S The analysis results are accurate and reliable.

[0042] The calibration module is used to calibrate the data acquisition and analysis module 4 to ensure the detection accuracy and data accuracy and reliability.

[0043] Online enrichment module 2-15 is used for online enrichment of cable trench VOC SIt has built-in activated carbon adsorption chamber 2-153, molecular sieve adsorption chamber 2-154, clay adsorption chamber 2-155, metal organic framework material adsorption chamber 2-156, polymer adsorption resin adsorption chamber 2-157, and is provided with a heating ring 2-158 and a thermal desorption interface 2-159 on the outside. Both sides are provided with a pin-type self-sealing joint composed of a groove-type part 2-151 and a tongue-type part 2-152 to adapt to the harsh high-sealing use environment and facilitate the disassembly and inspection of the module.

[0044] Online enrichment module 2-15 realizes cable trench VOC S The low-concentration components are efficiently enriched, and online monitoring and analysis are performed after thermal desorption, which overcomes the problem of high precision requirements for data acquisition and analysis modules. At present, the main online monitoring technologies include gas chromatography-mass spectrometry (GC-MS) analyzers and gas chromatography-hydrogen flame ionization detection (GC-FID) analyzers. The present invention adopts enrichment sampling to reduce the precision requirements for instruments, and realizes low-cost and efficient qualitative and quantitative analysis. At the same time, combined with the inspection module 2-14, the VOC inside the cable trench is fully implemented. S Dynamic monitoring and supervision not only ensures the safe operation of cable lines, but also reduces the workload and labor intensity of inspection and maintenance personnel, and provides data for fault trend prediction.

[0045] The control unit includes a DC24V power module, which supplies power to the data acquisition and analysis module 4 and the data processing and early warning module 5. The data terminal of the data acquisition and analysis module 4 is connected to the data processing and early warning module 5 for real-time and accurate collection and analysis of VOC in the cable trench. S The signal acquisition end of the data processing and early warning module 5 is connected to the emergency brake and vacuum gauge feedback signals, and the acquisition and analysis process is started or stopped when an emergency occurs and sampling is required.

[0046] The analysis control output terminal of the data acquisition and analysis module is connected to the output module. The control output terminal of the output module is divided into 18 channels. The 18 output channels are respectively connected to 18 intermediate relays KA1 to KA18.

[0047] The intermediate relay KA1 controls the opening and closing of the main power switch Q0 of the control unit, the intermediate relay KA2 controls the start and stop of the detection operation, the intermediate relay KA3 controls the opening and closing of the electric valve MV1, the intermediate relay KA4 controls the opening and closing of the electric valve MV2, the intermediate relay KA5 controls the opening and closing of the electric valve MV3, the intermediate relay KA6 controls the opening and closing of the electric valve MV4, the intermediate relay KA7 controls the opening and closing of the electric valves MV5 and V6, and the intermediate relay KA8 controls the opening and closing of the electric valve MV7.

[0048] The intermediate relay KA9 controls the opening and closing of the electric valve MV8, the intermediate relay KA10 controls the start and stop of the online enrichment module heating coil, the intermediate relay KA11 controls the start and stop of the condenser, the intermediate relay KA12 controls the start and stop of the booster pump, the intermediate relay KA13 controls the opening and closing of the electric valve MV9, the intermediate relay KA14 controls the opening and closing of the electric valve MV10, the intermediate relay KA15 controls the opening and closing of the electric valve MV11, the intermediate relay KA16 controls the start and stop of the sampling pump, the intermediate relay KA17 controls the start and stop of the vacuum pump, and the intermediate relay KA18 controls the start and stop of the buzzer.

[0049] At the same time, the data processing warning module is connected with a keyboard and a display, which are used for human-computer interaction, setting and displaying key parameters of the system working status.

[0050] Application Examples

[0051] ① Sampling joint arrangement

[0052] Press the sampling connector into Figure 2 , 3 The layered and segmented installation shown in the figure is carried out in a fire-proof separation area of ​​the cable trench. According to the actual laying situation of the substation, additional sampling joints and collection units are added to achieve VOC inside the cable trench of the entire station. S Dynamic monitoring and surveillance.

[0053] ②System self-cleaning

[0054] Preparation: Adjust the manual two-position three-way valve S1 to the appropriate position and confirm that the manual valve V1 is in the closed state.

[0055] Purge: The operation and maintenance personnel select the "Purge" option on the operation interface through the keyboard and confirm the selection. The system is in a reset state before startup, and all electric valves are in a closed state. After the operation and maintenance personnel click to start, the control program will trigger the intermediate relays KA14, KA2, and KA7. The relays are turned on to open the electric valves MV10, MV5, and MV6, open the manual ball valve V2, slowly open the nitrogen cylinder valve, and adjust the pressure of the pressure reducing valve to 0.02MPa. At this time, the sampling unit is purged. After 10 minutes, a pop-up window will display that the purge is completed. Close the nitrogen cylinder valve, the pressure reducing valve, and the manual ball valve V2. After clicking confirm, the system closes the electric valves MV10, MV5, and MV6.

[0056] Vacuum self-cleaning: Adjust the manual two-position three-way valve S1 to the appropriate position, open the manual ball valve V2, and then the operation and maintenance personnel select the "vacuum self-cleaning" option on the operation interface through the keyboard and confirm the selection. Before opening, the system is in the reset state and all electric valves are in the closed state.

[0057] After the operation and maintenance personnel click to start, the control program will trigger the intermediate relays KA15, KA2, and KA7. The relays will turn on and open the electric valves MV11, MV5, and MV6. After 30 seconds, the control program will trigger the intermediate relay KA17. The relay will turn on and turn on the vacuum pump for vacuum self-cleaning. When the system detects that the vacuum gauge VG reaches the threshold, a pop-up window will display that the vacuum self-cleaning is completed and the manual ball valve V2 is closed. After clicking confirm, the system will close the electric valves MV11, MV5, and MV6, and then turn off the vacuum pump after 30 seconds.

[0058] ③ Collection and analysis

[0059] Direct Procurement Analysis: The operation and maintenance personnel select the "Direct Procurement Analysis" option on the operation interface through the keyboard and confirm the selection.

[0060] Before starting, the system is in reset state and all electric valves are in closed state. After the operation and maintenance personnel click to start, the control program will trigger the intermediate relays KA2, KA3, KA6, KA8, KA12, KA13, and KA16, and the relays will turn on the electric valves MV1, MV4, MV7, and MV9. The booster pump will be turned on after 2 seconds, and the sampling pump will be turned on after 5 seconds. At this time, VOCS will be collected at a layered laying position in a certain fire separation zone of a certain section of the cable trench and the timing will start.

[0061] After 1 hour, the control program will trigger the intermediate relay KA4, the system will automatically close the electric valve MV1 and open the electric valve MV2. At this time, VOC is applied to another layered laying position in a fire separation zone of a certain section of the cable trench. S The data is collected and the timing starts. After 1 hour, the control program triggers the intermediate relay KA5, and the system automatically closes the electric valve MV2 and opens the electric valve MV3. At this time, VOC is measured at another layered laying position in a fire separation zone of a certain section of the cable trench. S Collect data and start timing, and then cycle through the tests.

[0062] The data acquisition and analysis module transmits the calculation results to the data processing and early warning module in real time for recording, analysis and early warning of possible faults of power combustibles such as cable sheaths. After the operation is completed, the system automatically shuts down the above operation.

[0063] Submit for inspection and analysis: Open the manual valve V1, and the operation and maintenance personnel select the "Submit for inspection and analysis" option on the operation interface through the keyboard and confirm the selection. Before opening, the system is in the reset state and all electric valves are in the closed state.

[0064] After the operation and maintenance personnel clicks on the start button, the control program will trigger the intermediate relays KA2, KA3, KA4, KA5, KA8, and KA12. The relays will open the electric valves MV1, MV2, MV3, and MV7, and the booster pump will be turned on after 2 seconds. At this time, VOC will be applied to a fire separation area in a certain section of the cable trench. SThe enrichment collection starts and the timing begins. After 2 hours, the system pops up a window to remind you that VOC is present in a fire separation area in a certain section of the cable trench. S Collection completed.

[0065] After confirmation, the system closes the electric valves MV7, MV1, MV2, MV3, and the booster pump. The operation and maintenance personnel take out the inspection module, label it, and put it into the tool box. Then connect other inspection modules to the collection unit, and repeat the above steps until the whole station is collected. The collected inspection modules are sent to the laboratory for instrument analysis, analysis and early warning of possible faults of power combustibles such as cable sheaths, reduce the fire hazards in the densely laid cable areas of substations, and improve the work efficiency of front-line operation and maintenance inspection personnel.

[0066] Online enrichment analysis: Open the manual valve V1, and the operation and maintenance personnel select the "Online Enrichment Analysis" option on the operation interface through the keyboard and confirm the selection. Before opening, the system is in the reset state and all electric valves are in the closed state.

[0067] After the operation and maintenance personnel clicks on the start button, the control program will trigger the intermediate relays KA2, KA3, KA4, KA5, KA7, KA8, and KA12. The relays will open the electric valves MV1, MV2, MV3, MV5, MV6, and MV7. After 2 seconds, the booster pump will be turned on. At this time, VOC will be applied to a fire separation area in a certain section of the cable trench. S The enrichment collection starts and the timing begins. After 2 hours, the system pops up a window to remind you that VOC is present in a fire separation area in a certain section of the cable trench. S Collection completed.

[0068] After confirmation, the system closes the electric valves MV7, MV1, MV2, MV3, MV5, MV6, and the booster pump, and closes the manual V1. The control program will trigger the intermediate relay KA10, and the relay will turn on the online enrichment heating ring for thermal desorption. When the temperature reaches the threshold, the system turns off the heating ring, and the control program will trigger the intermediate relays KA11, KA9, and KA16. The relay will turn on the electric valve MV8 and the condenser. After 5 minutes, the sampling pump will be turned on. At this time, VOC S Collection and analysis.

[0069] The above steps are repeated until the whole station is collected. The data collection and analysis module transmits the calculation results to the data processing and early warning module in real time for recording, analysis and early warning of possible faults of power combustibles such as cable sheaths. After the operation is completed, the system automatically closes the above operation.

[0070] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A VOC for substation cable trench S A monitoring system, characterized in that It includes a collection unit for collecting VOCs in cable trenches, a sampling and analysis unit, and a control unit. The collection unit includes a plurality of sampling joints arranged in the cable trench, a pretreatment gas circuit for converging and filtering and drying the plurality of sampling joints, a direct sampling branch, a test enrichment branch, an online enrichment branch, and a delivery gas circuit. The direct sampling branch, the test enrichment branch, and the online enrichment branch are connected in parallel. The sampling and analysis unit includes a purge air circuit, a vacuum air circuit, an atmospheric bypass air circuit, and a collection and analysis air circuit connected to the delivery air circuit pipeline. The purge air circuit is used to purge the collection unit with nitrogen before the collection test, and the vacuum air circuit is used to perform vacuum self-cleaning on the collection unit before the collection test. The inspection enrichment branch includes an adsorption sampling module that can be disassembled for inspection, the online enrichment branch includes an online thermal desorption adsorption sampling module and a thermal desorption inspection gas path connected to its thermal desorption interface, the thermal desorption inspection gas path is connected to the collection and analysis gas path, and the collection and analysis gas path is used to analyze the VOCs from the direct sampling branch and the thermal desorption inspection gas path. S Gas is analyzed online.

2. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that The gas delivery circuit includes a power delivery branch and a bypass branch, one of which is opened. The power delivery branch is provided with a booster pump, a voltage stabilizer and an electric valve. S It is opened when sampling. A manual valve V2 is provided on the bypass branch, which is opened during nitrogen purging and vacuum self-cleaning.

3. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that The pretreatment gas circuit includes several sampling branches, a main flow combiner, a quick connector, a dust filter, a manual two-position three-way valve S1 and a dryer, wherein each sampling branch includes several sampling hoses, a branch flow combiner, a 1# quick connector, a 2# quick connector, and an electric valve MV1, and each of the several sampling hoses is connected to a sampling connector.

4. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that The direct sampling branch is provided with an electric valve MV4, the inspection enrichment branch is only provided with an adsorption sampling module, and the online enrichment branch is provided with an electric valve MV5, an online thermal desorption adsorption sampling module and an electric valve MV6 in sequence.

5. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that A manual valve V2 is provided on the atmospheric bypass air path, which is opened during the enrichment sampling process in both the inspection enrichment branch and the online enrichment branch.

6. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that The adsorption sampling module is equipped with an activated carbon adsorption chamber, a molecular sieve adsorption chamber, a clay adsorption chamber, a metal organic framework material adsorption chamber, and a polymer adsorption resin adsorption chamber in sequence from inlet to outlet, and both ends of the adsorption sampling module are provided with ejector-type self-sealing joints.

7. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that The online thermal desorption adsorption sampling module is equipped with an activated carbon adsorption chamber, a molecular sieve adsorption chamber, a clay adsorption chamber, a metal organic framework material adsorption chamber, and a polymer adsorption resin adsorption chamber in sequence from inlet to outlet, and is provided with a heating coil and a thermal desorption interface on the outside.

8. The VOC for substation cable trench according to claim 7 S A monitoring system, characterized in that The thermal desorption gas delivery circuit includes a condenser and an electric valve MV8 which are connected to the thermal desorption interface in sequence. The condenser is used to heat the VOC S gas.

9. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that The collection and analysis gas circuit includes MV9, a sampling pump, and a data collection and analysis module which are sequentially connected by pipelines, wherein the data collection and analysis module is connected to the calibration module by pipeline and is in communication connection with the data processing and early warning module.

10. The VOC for substation cable trench according to claim 1 S A monitoring system, characterized in that The sampling method includes the following steps: S1. Install several sampling joints in layers and sections in the fire separation area of ​​the cable trench; S2, using the purge gas line to purge the inspection enrichment branch and the online enrichment branch with nitrogen, and the process ends after the set time is reached; S3, using the vacuum air line to perform vacuum self-cleaning on the inspection enrichment branch and the online enrichment branch, and the process ends when the set vacuum degree is reached; S4. Perform collection and analysis on the collection unit, including direct collection analysis, inspection analysis, and online enrichment analysis. The direct collection analysis is an online analysis in which a single sample is collected through a direct collection branch and sent to the sampling and analysis gas path. The inspection analysis is an offline analysis in which a single sample is collected through an inspection and enrichment branch and the adsorption sampling module is disassembled and sent to the inspection. The online enrichment analysis is an offline analysis in which a VOC sample is collected through an online enrichment branch and the thermal desorbed VOC sample is collected. S Sent to the sampling and analysis gas line for online analysis.

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