Guidelines for the assembly process of low-voltage switchgear and control equipment

1. Scope of application

This standard stipulates the assembly process requirements of the company’s low-voltage complete switchgear and control equipment (the operating environment altitude is lower than 2000m, and when the altitude exceeds 2000m, special treatment should be done.). When the user’s requirements or technical agreements have technical clauses that are higher than or higher than this standard, the user’s requirements or technical agreements shall be implemented.

2. Reference standards

GB7251.1-2005 “Low-voltage switchgear and control equipment, part one type test and partial type test complete equipment”

GB/T16934-1997 “Electric Energy Metering Cabinet”

JB/T5877-2002 “Low-voltage fixed closed switchgear”

GB50171-1992 “Code for Construction and Acceptance of Panels, Cabinets and Secondary Circuit Wiring of Electrical Installation Works”

GB50303-2002 “Code for Acceptance of Construction Quality of Electrical Construction Engineering”

3. Equipment and tools

Drilling machine, adjustable wrench, fixed wrench, Phillips screwdriver, straight screwdriver, manual hydraulic cold press pliers, paper cutter, electric drill, pneumatic screw gun, riveting gun, nameplate printer, 3-meter tape measure, iron hammer, bakelite hammer , Drill bits and taps of various specifications.

4. Process preparation

4.1 Prepare components and auxiliary materials according to the requirements of electrical system diagram, panel layout diagram, material list and drawings; components must pass the inspection and be accompanied by qualified marks and certificates; electrical components should have “3C” marks; The certified components or component surface coatings are moldy or blackened, and the surface of plastic parts is damaged or fragmented. They must not be installed.

4.2 According to the list of materials, check whether the model specifications, technical parameters, and quantity of the installed components meet the requirements of the drawings, whether the accompanying documents and accessories attached to the main electrical components are complete, and the documents and documents attached to the components when unpacking should be collected and submitted inspection department.

4.3 All components and fasteners should be placed on the workbench or on the special station equipment, and it is strictly forbidden to place them on the safe passage or pile them up randomly.

4.4 When the skeleton structural parts are white zinc-coated, the operator should wear clean gloves during the skeleton assembly and assembly, and keep the assembly site clean and tidy.

5. Cabinet assembly process requirements

5.1 After the sheet metal factory sends the cabinet, the workshop supervisor needs to do the following inspections:

5.1.1 According to the sheet metal drawing (panel opening drawing) provided by the technical department, check whether it meets the requirements of the drawing.

5.1.2 Check the structure of the cabinet to see whether the installation holes of primary components such as switches and mechanisms are correct.

5.1.3 Whether the cabinet body is deformed or the surface is damaged.

5.1.4 When the product skeleton is assembled, its verticality (measured by diagonal error), flatness, and gap error formed between structural elements shall comply with the provisions in Table 1.

5.1.5 Structure Before assembly, it should be checked whether the protection level of the shell meets the requirements of relevant standards (generally it should reach IP30).

5.1.6 The opening of the door should be flexible. The opening angle of the door should not be less than 90°.

5.1.7 The plating layer of electroplated parts should not have defects such as peeling, peeling, blackening, rusting, etc., and the parts with the above defects should be excluded during skeleton assembly.

5.1.8 The sprayed coating on the outer surface of the device should have good adhesion, and there should be no defects such as wrinkles, flow marks, blisters, impurities, brush marks, and through-ground color. The color should be uniform, and the surface coating should not have glare. Visual inspection at a distance of 1m from the device, there should be no obvious color difference between devices of the same batch and devices used side by side.

Table 1 Allowable error of skeleton assembly

5.2 The technical requirements for component installation are as follows:

5.2.1 The installation of electrical components shall comply with the requirements specified in the installation instructions and technical conditions (such as arcing distance, installation method, polarity, wiring method, spacing distance of heating elements and heat dissipation measures, etc.).

5.2.2 The installation layout of components should meet the requirements of the assembly arrangement diagram. When the assembly support is adjustable, the installation and adjustment of the components must meet the arcing distance, and the phase-to-phase and phase-to-ground electrical clearances and creepage distances between the main busbar and exposed live parts should also meet the requirements in Table 2. When the requirements in Table 2 cannot be met, composite insulation can be used.

Table 2 Minimum clearances and creepage distances

5.2.3 The horizontal busbars and branch busbars in the cabinet of low-voltage switchgear shall be covered with black 1000V insulating heat-shrinkable sleeves. If there are special requirements, they shall be covered with color-separated 1kV insulating heat-shrinkable sleeves. Meet the requirements of Table 3.

Table 3 Phase sequence color selection specification

5.2.4 The low-voltage capacitance compensation cabinet shall comply with the values in Table 4 when selecting the wire cross-section specifications according to the capacitor capacity. The connecting wires of the terminal piles of the capacitor device shall have insulation suitable for the rated working voltage, and adopt multi-strand black insulated soft wires with copper cores (single-strand color-separated hard wires for 6mm2 and below), and shall be equipped with insulated wires suitable for Cold crimp terminals.

Table 4 Capacitor capacity and wire cross-section selection table

5.2.5 Fasteners for structural parts and electrical components should be tightened without slipping, and anti-loosening measures should be taken. The tightening standard is based on the flattening of the spring washer, and the tightening bolts should expose 2 to 5 teeth of the nut. When assembling fasteners, washers, nuts, bolts, etc. should be smooth in appearance and evenly coated. When assembling the same electrical components and busbars, fasteners of the same variety and specification should be used for installation.

5.2.6 When the door of the box body is a conductor, a 2.5mm2 yellow-green double-color soft insulated wire should be used to reliably connect to the metal frame grounding. The claw-type washer should be used at the grounding screw to ensure that the grounding resistance is not greater than 0.1Ω. There must be an obvious grounding symbol at the grounding place.

5.2.7 The grounding of the low-voltage arrester should be connected in series with a TMY-15×3 and reliably connected to the grounding bar.

5.2.8 The grounding of low-voltage capacitors should be connected in series with a bare 4mm2 single-strand copper core hard wire and reliably connected to the grounding bar.

5.2.9 When the product frame and structural parts of the low-voltage switchgear are electroplated and assembled, the general grounding plate and the screws of the grounding plate shall be welded at appropriate positions near the main component mounting plates such as the frame circuit breaker, rotary knife switch, and knife fuse switch. The diameter should not be less than M10.

5.2.10 The grounding wire of low-voltage electrical appliances should be connected to the grounding plate with a cross-sectional area of not less than 10mm2 yellow and green double-colored wires from the grounding point of the electrical shell to the grounding plate, and keep in good contact.

5.2.11 The action of the mechanical interlocking device of the drawer should be correct and reliable. After the circuit breaker is opened, the primary connectors can be separated. In the disconnected position, the distance between the primary moving contact and the vertical bus bar or static contact should not be less than 20mm.

5.2.12 The push and pull of the drawer should be flexible and light, free from jamming and collision, and the functional units with the same rated current value should be interchangeable.

5.2.13 It should be ensured that the working position, test position and disconnection isolation position of each drawer unit are accurately and reliably in place.

5.2.14 A layer of conductive paste should be applied to the contact points of the primary moving contacts of the drawer to ensure good contact of the contacts.

5.2.15 A 2.5mm yellow-green double-color soft insulated wire should be used to connect the drawer measurement and control board to the metal frame of the drawer. Claw-type washers should be used at the ground of the measurement and control board to ensure that the grounding resistance is not greater than 0.1Ω.

5.2.16 The product nameplate, functional unit usage label, secondary component label, etc. should be marked correctly and completely, and meet the requirements of the technical drawings. Paste should be firm, eye-catching, uniform and even. The circuit mark of the feeder circuit breaker should be consistent with the location of the opening and closing indication marks.

5.2.17 The component label on the door panel should be pasted at an obvious position above the components to facilitate the operator to observe and identify. The use signboard of the drawer unit should be pasted above the hinge side of the drawer door, and the pasting size should be 10mm from the edge of the small drawer door up, down, left, and right.

5.2.18 Printing regulations for low-voltage equipment nameplate parameters:

Print the nameplate parameter table provided by the technical department, and the technician’s nameplate parameter table should be consistent with the “3C” certification report.

6. Process quality control

6.1 After the process is completed, self-inspection should be carried out in accordance with the process items in the “Low-voltage Complete Switchgear and Control Equipment Assembly Process Guidelines”, and sign in the corresponding signature column after passing the test.

6.2 Clean up the cabinet, and clean up the sundries that are not related to the product, such as: redundant thread ends, fasteners, assembly tools, etc.

6.3 Check whether all wiring points are connected reliably, whether all fasteners are fully fastened, and whether the identification and nameplate are correct, complete and clear.

6.4 The surface coating should not be damaged during assembly. For scratches and damages on the coating caused during the assembly process, paint should be repaired, and the color should be consistent with the color of the cabinet panel.

6.5 Check whether the door can be closed freely, whether the door lock is easy to operate, and whether the gap between the deadbolt and the door frame is appropriate.

6.6 Keep the product clean and the production site clean and tidy. There are no screws, nuts and other fasteners and wires and other sundries on the ground.

6.7 Submit inspection after self-inspection.