A distribution box contains a vast amount of data parameters. It is generally a low-voltage electrical wiring system that requires the assembly of switching equipment, measuring instruments, protective electrical devices, and auxiliary equipment in a closed or semi-closed metal cabinet or panel to form a low-voltage distribution box. During normal operation, the circuit can be connected or disconnected using manual or automatic switches.
A switch cabinet is an electrical device in which external power lines first enter the main control switch inside the cabinet, and then enter the branch control switches. Each branch circuit is configured according to its needs. Examples include instruments, automatic control systems, motor magnetic switches, various AC contactors, etc. Some switch cabinets also have high-voltage and low-voltage compartments and high-voltage busbars, such as those in power plants. Some also have underfrequency load shearing features to protect the main equipment.
The main function of a switchgear is to open, close, control, and protect electrical equipment during the power generation, transmission, distribution, and energy conversion processes in a power system. The main components of a switchgear include circuit breakers, disconnect switches, load switches, operating mechanisms, instrument transformers, and various protective devices. Switchgear can be classified in many ways, such as by the circuit breaker installation method (removable switchgear and fixed switchgear); or by the cabinet structure (open switchgear, metal-enclosed switchgear, and metal-enclosed armored switchgear); and by voltage level (high-voltage switchgear, medium-voltage switchgear, and low-voltage switchgear). It is mainly suitable for various applications such as power plants, substations, petrochemical plants, metallurgical steel rolling mills, light industry and textiles, factories and mines, residential communities, and high-rise buildings.
What are the general regulations for low-voltage electrical operation in rural areas?
1. An operation ticket (see Appendix D) should be filled out for low-voltage electrical operations. However, an operation ticket is not required if only one branch circuit is being stopped (or energized) and the number of operation items does not exceed three. An operation ticket must be filled out for any operation involving the installation or removal of grounding wires. Before operation, the names, numbers, and on/off positions of on-site equipment, switches, and knife switches should be checked and verified against the low-voltage system simulation diagram and operation sequence. After operation, a comprehensive inspection should be conducted.
2. Electrical operation sequence: When power is off, the switch should be turned off first, and then the knife switch should be turned off; when power is restored, the above operation sequence is reversed.
3. When closing the knife switch, the knife switch should be closed quickly when the moving contact is close to the stationary contact, but there should be no impact when the moving contact is close to the end of the closing operation; when pulling the knife switch, the knife switch should be opened quickly when the moving contact is about to leave the stationary contact, and then the operation should be continued to the end.
4. After operating the switch and knife switch, an inspection should be performed. After closing, check whether the three-phase contact is good and whether the interlocking operating handle is properly braked; after opening, check whether the three-phase moving and stationary contacts are disconnected, whether the air distance between the moving and stationary contacts is qualified, and whether the interlocking operating handle is properly braked.
5. If any questions or abnormal malfunctions are found during operation, operation should be stopped and continued only after the problem has been investigated and resolved.
6. Scheduled power outages and restorations are strictly prohibited.
7. It is strictly forbidden to cut off (send on) power to a line (main line or branch line) by removing (or putting on) the fuse.
The above content is compiled based on problems encountered by trainees in their actual work and is for reference only. Please communicate and correct any issues promptly.
What are the requirements for the electrical installations on the switch cabinet?
1. Electrical components meet design specifications, are in good condition, have all accessories, are neatly arranged, securely fixed, well-sealed, and perform as required. 2. Each electrical component can be disassembled and installed independently without affecting the fixing of other electrical components and wiring harnesses. 3. Instruments and relays that have been adjusted and tested should be carefully transported to the installation site, avoiding severe vibration; during installation, they should be installed according to the drawings, avoiding incorrect placement, and connections should be secure. 4. Vertically installed knife switches and fuses should have the power supply connected at the top and the load connected at the bottom; when horizontally installed, the power supply should be connected on the left side (facing the switch cabinet), and the load on the right side. 5. The power indicator lights of the switch cabinet should have their power supply connected to the outside (power supply side) of the main switch. 6. The neutral wire in the neutral system should be repeatedly grounded at the entry point and the end switch cabinet. 7. A "card frame" should be installed below all electrical components on the switch cabinet, indicating the name, group, rated current, etc.
Safety in using distribution boxes and switch boxes
Safety precautions for using distribution boxes and switch boxes:
1) Distribution boxes and switch boxes should be installed securely and be easy to operate and maintain.
2) Distribution boxes and switch boxes installed on the ground should be located on a flat surface and above the ground, and no debris should be piled up nearby.
3) The inlet and outlet of the distribution box and switch box should preferably be located at the bottom or side of the box, and the power supply lead should be run through a conduit and equipped with a waterproof elbow.
4) The wires in the distribution box and switch box should be well insulated, neatly arranged and firmly fixed, and the ends of the wires should be connected by bolts or crimping.
5) Distribution boxes with three or more circuits should be equipped with a main switch and branch switches. Each branch switch should not be connected to two or more electrical devices, nor should it be used by two or more work groups.
6) Distribution boxes that combine lighting and power should be equipped with knife switches or other types of switches respectively.
7) Electrical equipment such as contactors, knife switches, and switches installed in distribution boxes and switch boxes should operate flexibly, have good and reliable contact, and have no serious burning of contacts.
