1. Process Flow
2. Material Supply and Precautions
Product ordering should select products from the original two ministry designated certification manufacturers. Equipment ordering should be arranged to arrive when installation conditions are met. After equipment arrives on site, it should be stored in the on-site equipment warehouse, and the owner should be invited to jointly conduct an unpacking inspection. The manufacturer's technical documents should be complete, the model and specifications should meet the design requirements, and accessories and spare parts should be complete. The cabinet body should have no damage or deformation, the paint should be intact, and the internal electrical devices, components, and insulating porcelain parts should be complete without damage, cracks, or other defects.
3. Pre-Installation Preparation
Before installation, first verify whether the following civil works have been completed:
(1) Whether the roof and floor slabs have been constructed, and whether there is any leakage in the roof and ground;
(2) Whether the interior decoration works of the power distribution room and equipment room have been fully completed;
(3) Whether all types of embedded parts have been installed and meet the equipment installation conditions;
(4) Whether the doors and windows of the room have been installed;
(5) Whether all other processes that cannot be carried out after the start of equipment installation have been completed.
When installing high and low voltage cabinets, use a forklift to transport them along the underground first-floor car ramp to the nearest distance of the substation and distribution room, then use manual chain blocks for relocation. Power cabinets can be moved by manual labor. During transportation, they must be firmly fixed to prevent uneven force, cabinet deformation, or damage to components.
5. Fabrication and Installation of Foundation Steel
According to the drawings, cabinets are arranged in rows and installed on foundation steel. The power distribution room uses No. 10 channel steel. During fabrication, first straighten and level the bent channel steel, then prefabricate and process the foundation steel according to the drawings, and perform rust removal. After the foundation steel is fabricated, embed it in coordination with civil works according to the positions indicated in the drawings.
When installing the foundation channel steel, use a spirit level to level and align it. The unevenness and levelness of the foundation channel steel installation should be less than 1mm per meter and less than 5mm for the full length.
The embedded foundation channel steel of the distribution cabinet should be properly grounded. According to the design requirements, the grounding flat steel should be welded to the grounding grid at both ends, with the welding surface being twice the width of the flat steel.
When installing the cabinet body on the channel steel, use 0.5mm iron sheets for adjustment between the cabinet and the channel steel during alignment, but no more than 3 shims per location. After leveling and alignment, the panel surfaces should be consistent and neatly arranged. The cabinets and the side baffles should be tightened with bolts, and the gaps at the joints between cabinets should be less than 2mm
The grounding of the cabinet should be firm and good. Each cabinet should be separately connected to the foundation steel for grounding. A nose is welded on the side of the foundation steel at the lower left rear of each cabinet, and a copper conductor of not less than 6mm2 is used to firmly connect to the grounding terminal on the cabinet.
The cabinets are connected by busbars. The busbar correction, cutting, processing, installation, painting, and oil brushing should all comply with specification requirements.
After the distribution cabinet is in place, it should be fixed with bolts pressed against the foundation channel steel, and direct welding is strictly prohibited. When the distribution cabinets are arranged individually or in rows, the verticality, levelness deviation, panel surface deviation, and overall deviation of the gaps between cabinets should meet the requirements in the following table:
Serial No. Item Allowable Deviation (mm)
1 Verticality (per meter) <1.5
2 Levelness Top of adjacent two panels <2
Top of row of panels <5
3 Panel surface deviation Edge of adjacent two panels <1
Row of panel surfaces <5
4 Gap between panels <2
In this project, all distribution cabinets are equipped with separate working neutral busbars (N) and protective neutral busbars (PE) to connect the working neutral wire and protective neutral wire respectively. The doors of the distribution cabinets, regardless of whether there are electrical components on the door, should be connected to the PE busbar inside the cabinet using yellow-green two-color flexible wires.
6. Precautions
Before cabinet installation, pay attention to checking the following points to ensure usage requirements:
(1) The drawers should push and pull flexibly and lightly, without jamming or collision, and drawers of the same specification should be able to interchange flexibly.
(2) The mechanical interlock and electrical interlock devices of the drawers should operate correctly and reliably, and the disconnector can only be separated after the circuit breaker is opened.
(3) The center lines of the moving contacts and static contacts should be consistent, and the contacts should be in close contact to ensure that large currents passing through the contacts do not overheat. At the same time, the secondary circuit connection plugs between the drawer and the cabinet body should also maintain good contact.
(4) The contact between the drawer and the cabinet body, and between the cabinet body and the frame, should be good, and the grounding contacts between the drawer and the cabinet body should be tight. When the drawer is pushed in, the grounding contact should close before the main contact, and the opposite when pulled out.
The ordering and installation of low-voltage distribution cabinets should comprehensively consider the connection with external equipment, such as the connection with closed busbars and cable trays. The phase sequence of the reserved connection copper bars inside the cabinet should match the busbar trunking, and the phase spacing should be consistent. The sealing treatment between the cable entering the cabinet and the cabinet body should use tower-type rubber sealing rings, and the cable should be firmly fixed before entering the cabinet to prevent damage to the copper bars and electrical accessories inside the cabinet due to gravity.
During the installation of busbar electrical appliances inside the cabinet, the electrical clearance between exposed live parts of different phases and between exposed live parts and non-insulated metal frames should not be less than 20mm. If this requirement cannot be met, insulation protection measures must be taken.
7. Testing and Adjustment:
(1) Test content: high-voltage cabinet frame, busbars, lightning arresters, high-voltage porcelain insulators, voltage transformers, current transformers, high-voltage circuit breakers, etc.
(2) Adjustment content: adjustment of overcurrent relays, time relays, signal relays, and mechanical interlock adjustment.
(3) Insulation measurement: use a 500V megger to test the resistance of each circuit at the terminal board, and the value must be greater than 0.5 megohms.
(4) If the secondary circuit has transistors, integrated circuits, or electronic components, the inspection of that part must not use a megger, but should use a multimeter.
(5) Connect temporary control power and operating power, and simulate test control, interlocking, operation, relay protection, and signal actions respectively.
8. Power Transmission Operation and Acceptance
(1) Close the switch of the high-voltage incoming cabinet and check whether the voltage on the voltage transformer cabinet is normal.
(2) Close the switch of the transformer cabinet and check whether the transformer is energized.
(3) Close the switch of the low-voltage incoming cabinet and check whether the three-phase voltage on the voltmeter is normal.
(4) After 24 hours of no-load operation without abnormal conditions, the acceptance procedures can be processed.
