Q&A about low-voltage distribution cabinets -- Hazards
I. The Dangers of Low-Voltage Distribution Boxes
1. It is the lowest level of control and protection facility in the power system, and there is a high chance of contact with people;
2. They are numerous and widely distributed, making them difficult to manage;
3. It is easily affected by on-site conditions and is constantly changing;
4. Low-voltage distribution boxes mainly have metal casings, making them prone to faults such as leakage.
5. Many distribution boxes are in poor environments, making them prone to aging or damage.
II. Selection of Low-Voltage Distribution Boxes
The protection type of low-voltage distribution boxes should be selected based on the conditions of the workplace:
In locations with a relative humidity not exceeding 75% and a low risk of dust, corrosive gases or vapors, or flammable and explosive substances, open-type low-voltage distribution boxes can be selected.
Low-voltage switchgear related knowledge and maintenance methods
The maintenance of low-voltage distribution cabinets mainly aims to ensure their normal and safe operation. A comprehensive annual inspection and maintenance of the low-voltage distribution cabinets is necessary. Maintenance should be completed with minimal power outage time, generally with the power outage time determined for the homeowner one day in advance.
Maintenance procedures and steps for low-voltage distribution cabinets:
1. Maintenance should begin from the low-voltage side of the transformer. After de-energizing the distribution cabinet, clean the dust inside the cabinet, check whether the busbars and downleads are properly connected, whether the joints are overheating or discolored, check whether the cable heads and terminal blocks are secure and reliable, check whether the grounding wire is corroded, and whether the terminal blocks are tightened. All secondary circuit wiring connections should be reliable and the insulation should meet the requirements.
2. When inspecting drawer-type switches, the drawer-type switch cabinet should move smoothly when pushed in or pulled out, and the mechanical interlocking should be reliable. Check whether the automatic air switch operating mechanism on the drawer cabinet is in place and whether the wiring screws are tight. Clean the surface and surrounding area of the contactor contacts and check whether the contactor contacts are in good contact. If the contact is poor, the contact surface can be slightly filed if necessary. If the contacts are severely burned (the contact points are worn down to 1/3 of the original thickness), the contacts should be replaced. Power indicators and indicator lights should be in good working order.
Q&A about low-voltage distribution cabinets -- types
GCK cabinet: (MCC)
Main architecture
The basic structure of the cabinet is a modular assembly structure. It is bolted together, and the functional compartments are isolated from each other using 20mm modular mounting holes. A key feature of the GCK cabinet is that the busbar is located at the top of the cabinet, and its compartments are divided into functional unit compartments (front of the cabinet), busbar compartments (top of the cabinet), and cable compartments (rear of the cabinet). It can also be wall-mounted; in this case, the right side of the cabinet is widened by 200mm to serve as the cable compartment, resulting in a similar top busbar configuration to the MNS cabinet.
Functional Unit
The module for drawer height is 200mm.
MNS Cabinet: (MCC)
Main architecture
1. The basic structure of the cabinet is assembled from C-shaped profiles. These C-shaped profiles are made by bending steel plates with mounting holes of E=25mm.
2. The withdrawable MCC cabinet is divided into three compartments: a functional unit compartment (front left), a busbar compartment (rear), and a cable compartment (front right). Since the horizontal busbar compartment is at the rear, it can also be made into a double-sided cabinet.
3: To reduce the bandwidth of the switchgear, the main busbar is installed horizontally at the top of the switchgear, with the rear half of the cabinet serving as the cable compartment. In this configuration, the busbar layout is similar to that of the GCK switchgear.
