High-voltage switchgear is widely used in power distribution systems to receive and distribute electrical energy. The switch cabinet has the function of suppressing internal faults. "Internal faults" refer to faults caused by arc short circuits inside the switch cabinet. Once an internal fault occurs, it is required to limit the arc fault to the compartment. It can also be used to suppress the fault when the power equipment or circuit fails. Parts are quickly removed from the power grid to ensure the normal operation of fault-free parts of the power grid and the safety of equipment and operation and maintenance personnel. Therefore, high-voltage switchgear is a very important power distribution equipment, and its safe and reliable operation is of great significance to the power system.
At present, substations mainly use KYN type switch cabinets. Now we will take the 10kV switch cabinet model KYN28A-12 switch cabinet as an example to explain the overall structure of the switch cabinet.
Model identification
The KYN28A-12 switch cabinet is composed of a cabinet body and a central pull-out handcart. The cabinet adopts an assembled structure, connected with rivet nuts and high-strength bolts, and is divided into four separate compartments by metal partitions: A busbar room, B circuit breaker room, C cable room and D relay room , the top of the switch cabinet is equipped with pressure relief devices above the circuit breaker room, busbar room and cable room.
1. Bus room
The main busbar is a single unit spliced and connected through each other in the compartment. The main busbar is supported by insulators, and the branch busbars are connected to the primary static contact box and the main busbar through bolts.
The main busbar passing between adjacent cabinets is insulated from the cabinet body with an insulating sleeve. If an internal fault arc occurs, it can limit the accident from spreading to adjacent cabinets. It can effectively limit the accident to this compartment and at the same time support the busbar.
2. Circuit breaker room
Specific guide rails are installed inside the circuit breaker room, and the circuit breaker handcart slides and works inside, allowing the handcart to move between the working position and the test position. The static contact curtain (valve) installed on the rear wall of the handcart room automatically closes when the handcart moves from the working position to the test position, and opens automatically when the handcart is moved in the opposite direction. Ensure that operators do not touch live objects.
3. Cable room
The cable terminal connection room has a large space, which is convenient not only for the installation of primary cables, but also for the installation, replacement and maintenance of primary components such as current transformers, grounding switches, arresters, and live displays.
4. Relay instrument room
Relay protection components, instruments, live indicators, indicator lights, secondary power switches and other secondary equipment (protection pressure plates, operating handles) are installed in the relay instrument room.
5. Pressure relief channel (pay attention to main transformer cabinets and other cabinets with bridges)
During the operation of the switch cabinet, due to various reasons, such as the aging of the internal insulation, the internal fault of the switch cabinet is short-circuited. Under the short-circuit current of tens of thousands of amperes, gases with high temperature and high pressure can be generated instantly. If these gases cannot be contained in a small cabinet in a short time, Effective release within a certain period of time will cause the switch cabinet to explode, causing damage to adjacent cabinets, expanding the fault scope, and possibly causing casualties, so a pressure relief channel is designed.
