The installation specifications for medium and high-voltage switchgear

Installation Specifications for Medium and High Voltage Switchgear

The installation of medium and high voltage switch cabinets is a highly specialized and safety-critical task that must strictly adhere to national and industry standards (such as GB and DL/T standards), design drawings, and the technical requirements of the manufacturer. The following are the key points of the installation guidelines:

Carried out jointly with the supervisor, the owner, and the supplier. Check if the packaging is intact.

Verify that the equipment model, specification, and quantity are consistent with the drawings and the list.

Check if the appearance of the cabinet is scratched, deformed, or rusted, and if the paint layer is intact.

Check if the internal components, insulating parts, and busbars are damaged, damp, or fallen off.

Check if the technical documents with the cabinet (certificate of conformity, factory test report, manual, drawings) are complete.

Make a record of the unpacking inspection. If there are any problems, take photos and report them in time.

1. Handling and Hoisting:

Use professional hoisting equipment (such as nylon ropes) and strictly avoid using steel wire ropes to contact the cabinet body to prevent damage to the paint and structure.

Keep the cabinet stable and prevent severe vibrations, tilting or toppling. Usually, it should be lifted from the dedicated lifting points at the bottom.

2. Positioning and Arrangement:

According to the arrangement sequence specified in the design drawings, move the switchgear cabinets one by one onto the foundation channel steel.

Start from the reference cabinet on one side (usually the middle or the side close to the wall), and roughly position it first.

3. Adjustment and Fixation:

Levelness adjustment: Use a level gauge (with an accuracy of no less than 0.5mm/m) and spacers to adjust the verticality and levelness of the cabinet. Requirements: The verticality of a single cabinet should be less than 1.5mm/m, the top level deviation of the row of cabinets should be less than 2mm, and the top level deviation of adjacent cabinets should be less than 1mm.

Gap and flatness: Adjust the gap between adjacent cabinets to be tight and uniform (generally less than 1.5mm). The front of the row of cabinets should be on the same plane, and the deviation of the panel surface should be less than 1mm.

Fixation: After the adjustment is qualified, use welding or bolt connection methods to firmly fix the cabinet to the foundation channel steel. Direct welding on the cabinet is strictly prohibited. The tightening torque for bolt fixation should comply with the requirements.

Cabinet connection: Use the special bolts and connection plates provided by the manufacturer to reliably connect adjacent cabinets to ensure they form a whole. The busbar compartment partition should be installed in place and sealed properly.

Installation of Busbars and Internal Conductors

1. Inspection of Busbars: The surface of the busbar (copper strip or aluminum strip) should be smooth, flat, free of cracks and deformation. The soldering or silver plating on the connection surfaces should be intact.

2. Installation of Busbars:

Assemble according to the manufacturer's serial number and the order specified in the drawings.

Connection surface treatment: The connection surfaces must be clean, smooth, and free of oxide layers. Apply special power composite grease (conductive paste) and prohibit the use of industrial vaseline or other oils.

Fastening with bolts: Use a torque wrench and follow the manufacturer's specified torque and sequence (from the middle to both sides) to cross and diagonally tighten. The torque value must meet the standards to ensure the minimum contact resistance. The exposed length of the bolt head should be 2-3 bolts.

Safety distance: Strictly check the electrical safety clearances between the same phase, relative to the ground, and the energized body to the cabinet body and the door, and must comply with the standard requirements.

Phase marking: The phase sequence markings (A yellow, B green, C red) for the main busbar and branch busbars should be clear, correct, complete, and in the same position.

Check if the carriage track is flat and parallel. Ensure that the carriage can be easily pushed in and pulled out without any jamming.

The switchgear carriage should be accurately positioned and locked securely in the working position, test position, and open position.

The center of the moving and static contacts (isolating plugs) should be aligned, and the insertion depth should meet the requirements. The contact surfaces should be clean and a small amount of special lubricating grease can be applied.

Perform the mechanical operation test of the switchgear carriage to check if the "five prevention" interlocking function is reliable and flexible.

 Fixed Circuit Breaker: Install it firmly on the frame of the cabinet according to the instructions, and connect the main circuit and the operating mechanism.

1. Secondary Wiring:

Follow the design drawings and terminal block diagrams for wiring.

Use standard cross-sectional and color-coded multi-strand copper core insulated wires. The wiring should be correct, secure, neat, and clear.

The wire bundles should be neatly bundled and firmly fixed to avoid crossing. Leave an appropriate margin to avoid affecting the operation of the equipment and the opening and closing of the door panel.

Each terminal connection should not exceed two wires. The wire ends should be crimped onto dedicated copper terminals.

2. Grounding System Installation (Crucial):

Main Grounding Grid Connection: Connect at least two different points of grounding main lines (usually ≥ 40x4mm galvanized flat steel) from the main grounding grid of the substation to the high-voltage room.

Switch Cabinet Grounding Busbar: At the bottom of each row of switch cabinets, a dedicated and continuous grounding copper busbar (usually ≥ 40x4mm or 50x5mm copper busbar) should be set. This copper busbar should be reliably welded to the above two grounding main lines.

Cabinet Grounding: The metal frame and metal door panel of each switch cabinet should be reliably connected to the internal grounding busbar with a copper braided strip with an area of no less than 50mm². The connection points should use anti-loosening bolts.

Component Grounding: The grounding terminals of circuit breakers, transformers, lightning arresters, etc., should be connected to the internal grounding busbar with a dedicated grounding wire (such as ≥ 25mm² copper braided wire).

Through-type Grounding: The grounding busbars of the rows of cabinets should be reliably connected at both ends to the main grounding grid to ensure that the entire switch cabinet array is in the same equipotential ground grid.

 "Five-prevention" Interlock Function Inspection

After installation, each of the "five-prevention" functions must be checked item by item and strictly to ensure 100% reliability:

1. Prevent incorrect tripping or closing of circuit breakers (usually through coded locks or microcomputer anti-error systems).

2. Prevent opening or closing of disconnectors (or switchgear) while the load is on.

3. Prevent connecting grounding wires (closing grounding knife switch).

4. Prevent energizing with grounding wires (grounding knife switch closed).

5. Prevent entering energized compartments by mistake.

The installation of medium and high voltage switch cabinets is a systematic project. The core principle is "precision, firmness, reliability, and safety". Standardized operations must be adhered to, and the quality of busbar connections, grounding reliability, and the "five prevention" interlocking functions must be strictly controlled as the three vital lines. Through strict commissioning tests, the overall installation quality can be verified, ultimately ensuring that the equipment is safely and reliably put into operation.

KYN28-12 indoor armored metal-enclosed switch equipment (hereinafter referred to as KYN28-12 switchgear) is suitable for three-phase AC 50HZ, 7.2~17.5kV single busbar and single busbar sectionalized power system, with perfect "five-proof" function. The removable part of the switchgear cabinet can be equipped with extractable vacuum circuit breaker or vacuum contactor, isolation trolley, PT trolley and other components.