Construction method for installing feeder interval of local power outage of 6kV switch cabinet of thermal power plant

Abstract

The present application belongs to the technical field of high-voltage power distribution device expansion, and discloses a construction method for locally powering off and installing feeder interval of 6kV switch cabinet of thermal power plant, which comprises the following steps: realizing local power-off of operation area by load switching and transferring; confirming no-load or light-load state by measuring busbar current of operation section; installing insulation baffle and electromagnetic shielding cloth and reliably grounding; installing insulation piercing connector by phase for A phase, B phase and C phase; immediately carrying out double insulation recovery after installation of each phase and carrying out next phase after passing insulation test; returning load and monitoring temperature rise after completing installation of new cabinet body and debugging of protection device; formally putting into operation after no abnormality in load trial operation. The present application significantly improves construction safety and reliability of installing feeder interval, reduces construction cost and power generation loss, and is suitable for expansion of plant power, environmental protection reconstruction, energy saving upgrading and emergency repair engineering of thermal power plant.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage power distribution equipment expansion technology, and relates to a construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants. Background Technology

[0002] The 6kV power supply system of a thermal power plant is used to power key auxiliary equipment such as boiler induced draft fans, feedwater pumps, and condensate pumps. Its power supply reliability directly determines the safe and stable operation of the unit. In recent years, with the expansion of businesses such as ultra-low emission retrofitting, frequency conversion energy saving, industrial steam supply, and sludge co-firing in thermal power plants, the problems of insufficient number of feeder bays and capacity mismatch in the original switchgear have become increasingly prominent.

[0003] Currently, the conventional practice for adding feeder bays to existing switchgear is to wait for the unit's Class A or Class B overhaul, then shut down the entire 6kV busbar for 48 to 72 hours to complete the installation of the new cabinets, busbar connections, and protection system commissioning before restoring power. However, this method of modification has drawbacks such as significant economic losses, high coordination difficulties, and high safety risks.

[0004] To reduce power outage time, existing technologies have developed solutions using GIS (Gas-Insulated Switchgear) expansion modules. These solutions rely on double-isolation disconnect switches for safety isolation and physical connection via dedicated pre-reserved interfaces, enabling uninterrupted busbar expansion. However, GIS expansion modules place extremely high demands on the switchgear cabinet structure and busbar layout, requiring pre-reserved expansion interfaces in the original cabinet or large-scale structural modifications. This results in high costs, complex construction, and incompatibility with the large existing stock of conventional air-insulated metal-clad switchgear such as KYN28-12 and KYN61-40.5.

[0005] In addition, some literature has proposed a technical approach of using insulation piercing connectors to directly branch onto energized busbars. Insulation piercing connectors achieve electrical connection by piercing the main insulation layer of the busbar, eliminating the need to strip the insulation or cut the busbar, theoretically simplifying construction. However, conventional piercing connection technology is mostly used for branch connections of low-voltage insulated cables of 400V and below. Directly applying this technology to the busbars of 6kV medium-voltage switchgear presents problems such as inadequate insulation control, phase-to-phase interference and short-circuit risks, moisture-induced flashover, and risks associated with working under load.

[0006] Therefore, developing a safe, reliable, closed-loop, environmentally controlled, phase-to-phase interference-free method for installing feeder bays in conventional 6kV switchgear during partial power outages is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a construction method for adding feeder bays to 6kV switchgear in thermal power plants during partial power outages, in order to solve problems such as large losses from power outage modifications, poor compatibility of GIS uninterruptible power expansion modules, and insulation and phase-to-phase risks associated with conventional puncture connections in existing technologies.

[0008] To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0009] A construction method for adding feeder bays to a 6kV switchgear in a thermal power plant during partial power outages includes the following steps:

[0010] S1. Confirm that the capacity and channel of the backup circuit meet the load switching requirements, issue an operation ticket, and use a temporary cable to switch the load of the modification area to the backup circuit to achieve a partial power outage in the work area.

[0011] S2. After the load switching and transfer, measure the actual current of the busbar in the working section. If the actual current of the busbar in the working section is not greater than the preset current threshold, proceed to step S3. If the actual current of the busbar in the working section is greater than the preset current threshold, stop the subsequent operation, investigate the cause and handle it to meet the standard, and then proceed to step S3.

[0012] S3. Clean the cabinet and the busbar of the working section, install insulating baffles, lay electromagnetic shielding cloth and reliably ground the electromagnetic shielding cloth; maintain a safe distance between the insulating baffles and adjacent live parts.

[0013] S4. For the busbar piercing connection points in the cleaning operation section, install the insulation piercing connectors one by one in the order of phase A, phase B, and phase C, and tighten them to the rated tightening torque using a torque wrench; perform insulation restoration treatment on the insulation piercing connectors, and only proceed with the installation of the next phase after the insulation piercing connector of one phase has passed the insulation test.

[0014] S5. After the new cabinet is in place, adjust the level and verticality of the new cabinet, fix it and ground it, and then lay the cable, check the phase sequence and tighten the terminals.

[0015] S6. Enter the protection settings into the protection device of the newly added cabinet, use a relay protection tester to verify the protection settings, and complete the overcurrent and instantaneous overcurrent protection tests to verify the accuracy of the action;

[0016] S7. Maintain a partial power outage in the work area. First, remove the insulating baffle and electromagnetic shielding cloth, clean the work site, and confirm that there are no left-behind objects. Relocate the load according to the operation ticket. Use a thermometer to continuously monitor the temperature rise of the puncture connection point and the terminal block within a preset time. If the temperature rise is not greater than the preset temperature threshold, remove the temporary cable.

[0017] S8. Verify the construction process records, test data, and installation status of the newly added cabinets. After the load test run is completed without any abnormalities, the cabinets will be officially put into operation.

[0018] During steps S1 to S8, the relative humidity and condensation status inside the cabinet are continuously monitored. Construction can only proceed when the relative humidity is not greater than the preset humidity threshold and there is no condensation; otherwise, the process is paused and dehumidification is performed.

[0019] As a limitation, step S1 is preceded by:

[0020] S0. Verify the switchgear model, busbar specifications, bay layout, load parameters, and spare circuits; prepare operation procedure cards; inspect and accept insulation piercing connectors, insulation baffles, insulation self-adhesive tape, insulation sheaths, and temporary cables; and verify torque wrenches, thermometers, megohmmeters, and relay protection testers.

[0021] As a further clarification, the specific process of step S4 is as follows:

[0022] S41. Lightly grind the oxide layer off the pierced connection point of the busbar in the working section and wipe it dry;

[0023] S42. Install the insulation piercing connectors one by one in the order of phase A, phase B, and phase C, and tighten them to the rated tightening torque using a torque wrench.

[0024] S43. After the insulation piercing connector of each phase is installed and qualified, the insulation self-adhesive tape is half-overlapped and an insulation sheath is added. The insulation resistance is tested with a megohmmeter. If the insulation resistance is not less than the preset resistance threshold, it is qualified. The next phase can be installed after the insulation piercing connector of one phase is qualified.

[0025] As a further limitation, in step S42, each of phases A, B, and C shall be equipped with no less than two insulating piercing connectors;

[0026] The torque wrench is tightened in two stages to the rated tightening torque, which is 40 N·m to 60 N·m.

[0027] In step S43, the insulating self-adhesive tape is half-overlapped at least 5 layers, and the covering length exceeds the two ends of the insulating piercing connector by ≥50mm each.

[0028] The insulating sleeve is fastened to the outside of the insulating self-adhesive tape, and the insulating sleeve completely covers the insulating piercing connector and the lead-out terminals of the insulating piercing connector.

[0029] The preset resistance threshold is 1000MΩ.

[0030] As a further limitation, the insulating puncture connector is a torque self-locking puncture connector;

[0031] The insulating sleeve adopts a snap-on type insulating sleeve.

[0032] As a second limitation, in step S2, the preset current threshold is 5% of the rated current of the busbar in the working section;

[0033] In step S3, the safe distance between the insulating baffle and the adjacent live conductor meets the safety clearance requirements for 6kV power distribution equipment in GB 50060, DL / T5352, and DL / T639.

[0034] As a third limitation, in step S5, the horizontal deviation is ≤3mm / m and the vertical deviation is ≤2mm / m;

[0035] The grounding of the newly added cabinet should have a cross-sectional area of ​​≥50mm². 2 The copper conductor is connected to the power plant's grounding grid.

[0036] As a fourth limitation, in step S6, during the overcurrent and instantaneous overcurrent protection test, the operating time error is ≤ ±0.1s.

[0037] As a fifth limitation, in step S7, the preset time is 15~30min and the preset temperature threshold is 40K;

[0038] In step S8, after a 30-minute test run under load, and once the protection device has no alarms and the load is stable, the system is officially put into operation.

[0039] As a sixth limitation, the preset humidity threshold is 75%, and dehumidification is performed using a heater, dehumidifier, or desiccant.

[0040] The present invention, by adopting the above-described technical solution, achieves the following technical advancements compared to existing technologies:

[0041] (1) The entire process of this invention only involves short-term power outages during load switching, with a single power outage time of ≤2 hours. During construction, the unit maintains load operation without reducing output or shutting down, thus significantly reducing power generation losses.

[0042] (2) This invention eliminates safety hazards such as working under load, phase-to-phase short circuit, and flashover due to moisture by taking multiple measures such as confirming the no-load current of the busbar in the working section, phase-by-phase blocking construction, double insulation restoration, and full-process microclimate monitoring, and significantly improves safety.

[0043] (3) This invention does not rely on the dual isolation disconnect switch and dedicated reserved interface of the GIS uninterruptible expansion module. It can be adapted to conventional switch cabinets to form an independent and safe working space. It does not require cutting the busbar or modifying the cabinet structure. It is low in cost and easy to promote.

[0044] (4) The present invention monitors the relative humidity and condensation state inside the cabinet throughout the construction process. Construction can only be carried out when the humidity is not greater than the preset humidity threshold and there is no condensation, thus eliminating the risk of flashover due to moisture from an environmental perspective.

[0045] In summary, this invention significantly improves the construction safety and reliability of adding feeder bays, reduces construction costs and power generation losses, and is applicable to power plant auxiliary power capacity expansion, environmental protection renovation, energy-saving upgrades, and emergency repair projects. Attached Figure Description

[0046] Figure 1 The diagram shows a flowchart illustrating the construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants, as described in an embodiment of the present invention. Detailed Implementation

[0047] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Example

[0049] like Figure 1 As shown, this embodiment is a construction method for adding feeder bays to a 6kV switchgear in a thermal power plant during a partial power outage. In this embodiment, "partial power outage" means that during the entire construction process, the thermal power unit remains connected to the grid and the 6kV busbar is energized throughout. The partial power outage is achieved only by transferring the load to take the feeder bay of the switchgear to be modified out of operation, while the busbar and other power supply feeder bays always maintain normal power supply status.

[0050] This embodiment includes the following steps:

[0051] S0. Pre-construction preparation:

[0052] Verify the switchgear model, busbar specifications, bay layout, load parameters, and spare circuits; prepare operation procedure cards; inspect and accept insulation piercing connectors, insulation baffles, insulation self-adhesive tape, insulation sheaths, and temporary cables; and verify torque wrenches, thermometers, megohmmeters, and relay protection testers.

[0053] Among them, the insulating puncture connector adopts the torque self-locking puncture connector; the insulating sleeve adopts the snap-on insulating sleeve; and the megohmmeter is a 2500V megohmmeter.

[0054] S1, Load switching and transfer:

[0055] Once it is confirmed that the capacity and channel of the backup circuit meet the load switching requirements, an operation ticket is issued, and a temporary cable is used to switch the load of the area to be modified to the backup circuit, thereby achieving a partial power outage in the work area.

[0056] S2. Confirmation of no-load current of busbar in the working section:

[0057] After the load switching and transfer, the actual current of the busbar in the working section is measured with a clamp meter. If the actual current of the busbar in the working section is not greater than 5% of the rated current of the busbar in the working section, then proceed to step S3 to meet the conditions for partial power outage operation and confirm the no-load or light-load state of the busbar in the working section. If the actual current of the busbar in the working section is greater than 5% of the rated current of the busbar in the working section, then the subsequent operation is stopped and the cause is investigated, such as incomplete load transfer, the existence of other untransferred loads, abnormality of the backup circuit, or measurement error. After the condition is met, proceed to step S3.

[0058] S3. Insulation protection installation:

[0059] Clean the dust and oil stains from the cabinet and the busbars of the working section; install insulating baffles between adjacent live parts, and ensure that the safe distance between the insulating baffles and adjacent live parts meets the safety clearance requirements for 6kV power distribution equipment in GB 50060, DL / T5352, and DL / T639.

[0060] Electromagnetic shielding cloth with conductive properties is laid around the busbar of the working section, and the electromagnetic shielding cloth is passed through a cross-sectional area of ​​not less than 4mm². 2 The copper grounding wire is reliably connected to the grounding busbar of the switchgear or the on-site construction grounding terminal to block electromagnetic interference and prevent static electricity accumulation.

[0061] S4. Phase-by-phase piercing connection and double insulation:

[0062] For the busbar piercing connection points in the cleaning operation section, install the insulation piercing connectors one by one in the order of phase A, phase B, and phase C, and tighten them to the rated tightening torque using a torque wrench; perform insulation restoration treatment on the insulation piercing connectors, and only proceed to the next phase after the insulation piercing connector of one phase has passed the insulation test.

[0063] The specific process for this step is as follows:

[0064] S41. Lightly sand the oxide layer at the puncture connection point of the working section busbar with fine sandpaper, and wipe it dry with alcohol.

[0065] S42. Install the insulation piercing connectors one by one in the order of phase A, phase B, and phase C. Install no less than 2 insulation piercing connectors on each phase and tighten them to the rated tightening torque in two stages using a torque wrench. The rated tightening torque is 40 N·m to 60 N·m.

[0066] S43. After the insulation piercing connector of each phase is installed and qualified, use insulating self-adhesive tape to half-overlap at least 5 layers, with the covering length exceeding the two ends of the insulation piercing connector by ≥50mm; and fasten the insulating sheath to the outside of the insulating self-adhesive tape to completely wrap the insulation piercing connector and its lead-out terminals.

[0067] Test the insulation resistance with a megohmmeter. The insulation resistance is qualified if it is ≥1000MΩ. Install the next phase only after the insulation of one-phase insulation piercing connector is qualified. That is, after phase A is fully insulated and qualified, construction of phase B can be carried out; phase C can be carried out only after phase B is completed. Simultaneous construction of two or more phases is strictly prohibited. Wherein, the preset resistance threshold is 1000MΩ, which is set according to DL / T 596-2021 *Preventive Test Code for Power Equipment* (Chapter 13).

[0068] S5. In-place fixing of new cabinet and cable connection:

[0069] After the new cabinet is in place, adjust the levelness of the new cabinet with a level, and the levelness deviation shall be ≤3mm / m; adjust the verticality with a magnetic plumb, and the verticality deviation shall be ≤2mm / m; then firmly fix the new cabinet to the foundation channel steel with bolts. After fixing, reliably ground the grounding terminal of the new cabinet to the power plant grounding grid with a copper conductor with a cross-sectional area of ≥50mm²; finally carry out cable laying, phase sequence checking and terminal tightening.

[0070] S6. Commissioning of protection device:

[0071] Enter the protection setting values into the protection device of the new cabinet according to the setting list, check the protection setting values with a relay protection tester, and then simulate faults to perform overcurrent and instantaneous overcurrent protection tests: set the relay protection tester to output 1.2 times the rated current value and start timing at the same time. The protection device shall issue a tripping command within the set action time, and the error between the measured action time and the set action time shall be ≤±0.1s. All protection items shall be checked and qualified.

[0072] S7. Load reconnection and removal of temporary equipment:

[0073] Maintain the local outage state of the working area. First remove the insulating baffle and electromagnetic shielding cloth, clean the working site, and confirm that no objects are left; reconnect the load according to the operation order, use a temperature measuring instrument to continuously monitor the temperature rise of the piercing connection point and the connection terminal within 15 to 30 minutes, and remove the temporary cable after confirming that the temperature rise is ≤40K. Wherein, the preset temperature threshold is 40K, which is set according to GB / T 11022-2020.

[0074] S8. Acceptance and commissioning:

[0075] Check the construction process records, test data and installation status of the new cabinet, conduct a 30-minute trial operation with load, and formally put into operation after the protection device has no alarm and the load is stable.

[0076] This embodiment also includes microclimate environment control: during the entire construction process of steps S1 to S8, the relative humidity and condensation status inside the cabinet are continuously monitored. Construction can only be carried out when the relative humidity inside the cabinet is ≤75% and there is no condensation. If the relative humidity exceeds the standard or condensation occurs, the operation is suspended and dehumidification is carried out using a heater, dehumidifier or desiccant. Work can only resume after the standard is met.

[0077] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants, characterized in that, Includes the following steps: S1. Confirm that the capacity and channel of the backup circuit meet the load switching requirements, issue an operation ticket, and use a temporary cable to switch the load of the modification area to the backup circuit to achieve a partial power outage in the work area. S2. After the load switching and transfer, measure the actual current of the busbar in the working section. If the actual current of the busbar in the working section is not greater than the preset current threshold, proceed to step S3. If the actual current of the busbar in the working section is greater than the preset current threshold, stop the subsequent operation, investigate the cause and handle it to meet the standard, and then proceed to step S3. S3. Clean the cabinet and the busbar of the working section, install insulating baffles, lay electromagnetic shielding cloth and reliably ground the electromagnetic shielding cloth; maintain a safe distance between the insulating baffles and adjacent live parts. S4. For the busbar piercing connection points in the cleaning operation section, install the insulation piercing connectors one by one in the order of phase A, phase B, and phase C, and tighten them to the rated tightening torque using a torque wrench; perform insulation restoration treatment on the insulation piercing connectors, and only proceed with the installation of the next phase after the insulation piercing connector of one phase has passed the insulation test. S5. After the new cabinet is in place, adjust the level and verticality of the new cabinet, fix it and ground it, and then lay the cable, check the phase sequence and tighten the terminals. S6. Enter the protection settings into the protection device of the newly added cabinet, use a relay protection tester to verify the protection settings, and complete the overcurrent and instantaneous overcurrent protection tests to verify the accuracy of the action; S7. Maintain a partial power outage in the work area. First, remove the insulating baffle and electromagnetic shielding cloth, clean the work site, and confirm that there are no left-behind objects. Relocate the load according to the operation ticket. Use a thermometer to continuously monitor the temperature rise of the puncture connection point and the terminal block within a preset time. If the temperature rise is not greater than the preset temperature threshold, remove the temporary cable. S8. Verify the construction process records, test data, and installation status of the newly added cabinets. After the load test run is completed without any abnormalities, the cabinets will be officially put into operation. During steps S1 to S8, the relative humidity and condensation status inside the cabinet are continuously monitored. Construction can only proceed when the relative humidity is not greater than the preset humidity threshold and there is no condensation; otherwise, the process is paused and dehumidification is performed.

2. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 1, characterized in that, Step S1 is preceded by: S0. Verify the switchgear model, busbar specifications, bay layout, load parameters, and spare circuits; prepare operation procedure cards; inspect and accept insulation piercing connectors, insulation baffles, insulation self-adhesive tape, insulation sheaths, and temporary cables; and verify torque wrenches, thermometers, megohmmeters, and relay protection testers.

3. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 2, characterized in that, The specific process of step S4 is as follows: S41. Lightly grind the oxide layer off the pierced connection point of the busbar in the working section and wipe it dry; S42. Install the insulation piercing connectors one by one in the order of phase A, phase B, and phase C, and tighten them to the rated tightening torque using a torque wrench. S43. After the insulation piercing connector of each phase is installed and qualified, the insulation self-adhesive tape is half-overlapped and an insulation sheath is added. The insulation resistance is tested with a megohmmeter. If the insulation resistance is not less than the preset resistance threshold, it is qualified. The next phase can be installed after the insulation piercing connector of one phase is qualified.

4. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 3, characterized in that, In step S42, each of phases A, B, and C shall be equipped with no less than two insulating piercing connectors; The torque wrench is tightened in two stages to the rated tightening torque, which is 40 N·m to 60 N·m. In step S43, the insulating self-adhesive tape is half-overlapped at least 5 layers, and the covering length exceeds the two ends of the insulating piercing connector by ≥50mm each. The insulating sleeve is fastened to the outside of the insulating self-adhesive tape, and the insulating sleeve completely covers the insulating piercing connector and the lead-out terminals of the insulating piercing connector. The preset resistance threshold is 1000MΩ.

5. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 4, characterized in that, The insulating puncture connector is a torque self-locking puncture connector. The insulating sleeve adopts a snap-on type insulating sleeve.

6. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 1 or 2, characterized in that, In step S2, the preset current threshold is 5% of the rated current of the busbar in the working section; In step S3, the safe distance between the insulating baffle and the adjacent live conductor meets the safety clearance requirements for 6kV power distribution equipment in GB 50060, DL / T5352, and DL / T639.

7. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 1 or 2, characterized in that, In step S5, the horizontal deviation is ≤3mm / m and the vertical deviation is ≤2mm / m; The grounding of the newly added cabinet should have a cross-sectional area of ​​≥50mm². 2 The copper conductor is connected to the power plant's grounding grid.

8. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 1 or 2, characterized in that, In step S6, during the overcurrent and instantaneous overcurrent protection test, the operating time error is ≤ ±0.1s.

9. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 1 or 2, characterized in that, In step S7, the preset time is 15~30 min, and the preset temperature threshold is 40K; In step S8, after a 30-minute test run under load, and once the protection device has no alarms and the load is stable, the system is officially put into operation.

10. The construction method for adding feeder bays during partial power outages of 6kV switchgear in thermal power plants according to claim 1 or 2, characterized in that, The preset humidity threshold is 75%, and dehumidification is performed using a heater, dehumidifier, or desiccant.

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