Knkong Electric Co.,Ltd

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Switchgear in high and low voltage equipment

mv switchgear

Switchgear (also known as a complete set of switches or a complete set of power distribution devices) is a circuit breaker-based electrical equipment, which refers to the electrical equipment manufacturers according to the requirements of the primary electrical wiring diagram, the relevant high and low voltage electrical appliances (including control appliances, protection appliances, Measuring appliances) and busbars, current-carrying conductors, insulators, etc. are assembled in a closed or open metal frame, as a device for receiving and distributing electrical energy in the power system.

Normal use condition of the switchgear
Surrounding environment: the ambient air temperature does not exceed 40℃ (upper limit), the general area is -5℃ (lower limit), and the cold area can be -15℃. If the ambient temperature is too high, the conductivity of the metal will be reduced, the resistance will increase, and the surface oxidation will be intensified; on the other hand, the excessive temperature will also greatly shorten the life of the insulation parts in the cabinet, and the insulation strength will be reduced. On the contrary, the ambient temperature If it is too low, internal stress will be generated in the insulation, which will eventually lead to the destruction of the insulation.
Altitude: generally not more than 1000 meters.
Environmental humidity: The daily average value is not greater than 95%, and the monthly average value is not greater than 90%.
Earthquake intensity: The sensation does not exceed 8 degrees.
Other conditions: Keep away from fire, explosives, severe pollution, chemical corrosion, and violent vibration.
Classification of high-voltage switchgear


structure type:
Armored type: each room is separated and grounded by a metal plate, such as KYN type
Spaced: each room is separated by one or more non-metallic plates, such as JYN type
Box type: The circuit breaker handcart itself is grounded and pushed into the cabinet
Circuit breaker placement:
Floor-type: The circuit breaker handcart itself is grounded and pushed into the cabinet
Center-mounted: the handcart is installed in the middle of the switch cabinet, and the loading and unloading of the handcart requires the loading car


Insulation type:
Air-insulated metal-enclosed switchgear
SF6 gas-insulated metal-enclosed switchgear (inflatable cabinet)
Composition of high voltage cabinet
Busbar room, circuit breaker room (handcart room), cable room, relay room
The busbar room includes:
Busbar bushing (supports and fixes the busbar and insulates the busbar from the cabinet);
Main bus: (collect and distribute electric energy);
Branch bus (from the branch from the main bus to the static contact on the top of the circuit breaker);
Static contact box (supports and fixes the static contact on the upper mouth of the circuit breaker, and insulates the static contact on the upper mouth from the cabinet);


The cable room includes:
Current transformer, outgoing high-voltage cable, overvoltage protection (arrester), voltage sensor, grounding knife gate, temperature and humidity sensor, heater
The handcart room includes:
Handcart track: for the guidance and positioning of handcart when moving in the cabinet
Static contact box partition: During the movement of the test position and the working position of the trolley, the shutters of the upper and lower static contact boxes are automatically opened or closed accordingly to form an isolation room for effective isolation.
Control panel and relay room
Microcomputer protection device
Multi-function electric energy meter
Automatic temperature and humidity controller
Household high-voltage electrified display device
Energy storage switch
Transfer switch
Opening and closing switch
Protection tripping pressure plate (after exit, when the compliance equipment fails, the comprehensive protection device will only send an alarm signal, but it will not cause the circuit breaker to trip. Generally, there is no need to change during the power-off operation, and it should be kept in the normal operation state)

Auxiliary equipment
Small power switch for secondary equipment:
The control includes the power supply of integrated measurement and control protection devices, an integrated display device, opening, and closing circuit, auxiliary equipment, etc. The power supply has AC and DC.
Cabinet top small bus:
It is arranged on the top of the switch cabinet relay instrument room and runs through the entire section of the power distribution cabinet, including DC small bus, AC small bus, and voltage small bus.
DC small bus provides DC power for the electrical equipment in a single switch cabinet. Its total power is led from the DC screen of the PLU room to the DC small open circuit in each switch cabinet on the high voltage room section. 10KV shares the DC small bus on the top of the cabinet.


AC small bus: provides AC power for the electrical equipment in a single switch cabinet, and its total power is led from the drawer cabinet in the low-voltage room to the small AC switch in each switch cabinet on the high-voltage room section (temperature and humidity automatic controller, sensor, heater, and Cable indoor lighting power supply)
Small voltage bus: provides voltage signal for the comprehensive protection device in a single switch cabinet, and its total power comes from the secondary circuit of the bus PT of this section (bus section PT secondary winding → bus section PT secondary winding small open-circuit → voltage small bus →Small DC switch in each switch cabinet on the section), the computer protection device will lose the voltage signal after the failure or power failure (the alarm signal "low voltage alarm" will be issued accordingly), the equipment will lose the voltage protection, and it will also cause the protection to malfunction.


Switchgear interlocking device
The switchgear has a reliable interlocking device, which meets the requirements of five-proof, and effectively guarantees the safety of operators and equipment.
A prompt button or change-over switch is installed on the door of the instrument room to prevent accidental switch-on and circuit breaker
When the circuit breaker handcart is in the test position or working position, the circuit breaker can only perform the closing operation, and after the circuit breaker is closed, the handcart cannot move, which prevents the load from being pushed or pulled by mistake.
Only when the grounding switch is in the open position, the circuit breaker handcart can move from the test position to the working position, and only when the circuit breaker handcart is in the test position, the grounding switch can perform the closing operation, thus realizing the prevention of live misoperation Earthing switch to prevent the circuit breaker from closing when the earthing switch is in the closed position
When the grounding switch is in the open position, neither the lower door nor the rear door of the switchgear can be opened to prevent accidentally entering the live interval
When the circuit breaker handcart is in the test or working position and there is no control voltage, it can only be opened manually but not closed


The interlocking of electrical appliances can be realized between cabinets
The connection between the secondary line on the switchgear and the second line on the circuit breaker handcart is achieved through a manual secondary plug. The moving contacts of the second plug are connected to the circuit breaker handcart through a nylon corrugated shrink tube. The secondary static contact seat is installed at the upper right of the switch cabinet handcart. The circuit breaker handcart can only be plugged and unplugged when the test and disconnection positions are in place. Due to the mechanical interlock when the circuit breaker handcart is in the working position The secondary plug is locked and cannot be released.

Date:2020-05-12 09:40

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