Basic knowledge of high and low voltage switchgear equipment

High and low voltage switchgear equipment and control cabinet is used for power generation, transmission, distribution, power conversion and power consumption equipment control. The switchgear has simple and reliable "five prevention" interlock function, and can prevent misoperation. The appearance is novel, flat, simple, and has uniform color. The high pressure indoor secondary line groove adopts all-metal protection, the operation is safer and more reliable, with a more humanized man-machine interface, explosion-proof operation and other characteristics.

What is a switchgear?

Switchgear (switch cabinet) is a kind of electrical equipment, the switch cabinet outside line will go into the main control switch of the cabinet firstly, and then into the sub-control switch. Each branch is set according to its need, such as instrument, automatic control, motor magnetic switch, various AC contactors, etc. Some switchgears are also equipped with high pressure chamber and low pressure chamber switchgear with high pressure bus, such as power plants, etc.

The role of switchgear

The main role of switchgear like metal clad switchgear is to open and close, control and protect electrical equipment in the process of power generation, transmission, distribution and energy conversion in the power system. The main parts of the switchgear are circuit breaker, disconnecting switch, load switch, operating mechanism, mutual inductor and various protection devices.

The five defenses of the switchgear

A) After the vacuum circuit breaker trolley in the HV switchgear is closed at the test position, the trolley circuit breaker cannot enter the working position. (Prevent closing with load)

B) When the grounding knife in the HV switchgear is in closing position, the trolley circuit breaker cannot enter and close. (Prevent closing with ground wire)

C) When the vacuum circuit breaker in the high voltage switch cabinet is in closing work, the back door of the panel cabinet shall be closed with the machinery on the ground cutter. (Prevent accidental entry into the charged interval)

D) The vacuum circuit breaker in the HV switchgear is closed during operation, and the grounding knife cannot be put into operation. (Prevent live grounding wire)

E) The vacuum circuit breaker in the HV switchgear cannot exit the working position of the trolley circuit breaker when it is working and closing. (Prevent pulling the switch with load)

The classification of switchgear

There are many classification methods of switchgear, including:

A) According to the circuit breaker installation mode, it can be divided into removable switchgear and fixed switchgear;

B) According to the different structure of the cabinet, it can be divided into open switch cabinet, metal closed switch cabinet and metal clad switchgear;

C) According to different voltage levels, it can be divided into high voltage switchgear, medium voltage switchgear mv panels and low voltage switchgear lv switchgear, etc.

High and low voltage switchgear maintenance

A) Maintenance of vacuum circuit breaker. Clean the circuit breaker insulator and vacuum chamber and wipe clean with a rag. Check the energy storage spring should have no deformation, no corrosion phenomenon. The drive shaft rotates flexibly and is lubricated. All parts and components should be in good condition. Because of the vibration of the opening and closing, the screw and the split pin are loose and interfere with the normal work. Therefore, the fixed screw and the split pin should be complete and reliable. The bolt connection of each part is strong and the force is uniform. Check the three-phase contact spring should have no deformation, contact surface has no heating and discoloration phenomenon.

B) Maintenance of microcomputer protection unit. Clean the external terminals of the protection unit and clean them with a dry flat oil brush. All parts should be in good condition without loosening and heating. The protection value and the pressure plate should be checked and the protection unit should be checked. The unit type should be carefully checked before replacing the protection unit, and two versions of drawings and construction plan should be provided according to the new protection unit and submitted to the electronic control department for approval before proceeding.

C) Maintenance of current transformer. Wipe the surface of the transformer with a rag and check that the secondary terminals and iron core of the transformer are well grounded. The current transformer shall be checked after all primary lines are removed. When replacing the current transformer, the equipment model shall be carefully checked. The device can be replaced before being checked first.

D) Over-voltage absorption device maintenance. Wipe the surface with a rag, primary line is removed, primary line is strictly prohibited to pull. Verify according to the rules, and replace unqualified one.

E) Minor repair of all items.