Analysis Of Air Insulated Switch Cabinet

Analysis of Air Insulated Switch Cabinet

A typical air insulated switchgear, such as KYN28 and 28 cabinets, also known as mid mounted cabinets, adopts air insulation, mid mounted functional handcart, and metal armored design. The switchgear is separated by metal partitions into four independent compartments: busbar compartment, handcart compartment, cable compartment, and instrument compartment, meeting the level of loss of operational continuity LSC2B, that is, functional units and cable compartments can be repaired when the busbar compartment is live; When the incoming cable is electrified, the bus compartment can be overhauled to ensure the continuity of power supply. The failure of one switch cabinet will not lead to the power failure of the whole row of cabinets, nor will the internal Arc fault of one switch cabinet lead to fire and continuous operation, and all switch cabinets will be burned. The partition level of the switchgear includes PM and PI levels, that is, the partition, valve, etc. are all made of metal, which is PM level. Anyway, if it is an insulation board, it is PI level.

The central functional handcart includes circuit breaker, isolation, Voltage transformer, metering and other handcarts. The handcart is equipped with a chassis car to drive the functional handcart to switch between the test position and the working position. Generally, the swing in distance is 200 mm. The functional module has a primary contact arm and contact. For example, the upper and lower poles of the circuit breaker have contacts to realize the connection and disconnection of the line and play the role of isolation. The Voltage transformer module has only one side of the contact to realize the acquisition of high voltage. The functional module contacts are dynamically connected to the static contacts inside the switchgear contact box. The contact box activates electrical insulation shielding and mechanical support. There is a valve plate in front of the contact box, and the valve mechanism drives the valve to open or close as the handcart enters and exits the contact box to ensure that all live parts (static contacts) are metal shielded and personnel do not touch high-voltage live parts after the handcart exits the compartment. The signal transmission and operation control of the module are connected to the switchgear through secondary plugs.

The width of the switchgear with a current of 1250A is generally 800mm, the depth is 1400mm, and the height is 2200mm. The width of the switchgear with a current of 2500A and above is 1000mm. The width of the miniaturized central cabinet is 550/600mm.

The air cabinet is not only a central cabinet, but also an XGN fixed cabinet and a three in one side mounted switch cabinet. The circuit breaker is fixed and installed inside the cabinet, and the upper and/or lower isolation switches are in a box structure, which is different from the armored structure. The box structure is where all high-voltage components and busbars are installed in one box with less internal separation, generally meeting the requirements of LSC1 or LSC2, that is, if any part of the switch cabinet malfunctions, the entire switch cabinet needs to be powered off, The continuity of power supply cannot be guaranteed.

XGN is relatively mature, and there is also a KGN type switchgear, which can achieve a current of 5000 or even 6300A. The short-term withstand current for 3 seconds can also reach 50 or 63kA. For special applications such as steel mills with large loads, fixed type reduces dynamic connection heating, and multiple contacts of the isolation switch are connected in parallel, which can carry large currents and withstand high short-circuit currents.

The three-in-one switch adopts a side mounted vacuum circuit breaker and is designed with an integrated isolation and grounding switch. The advantage is that it is highly integrated and compact, reducing the length of the conductive circuit, resulting in low heating. The isolation contact is directly connected to the busbar contact of the switchgear, and the operating mechanism is integrated inside a mechanical box. Sequential operation and mechanical interlocking are simple and reliable, without the need for additional propulsion and interlocking mechanisms. The side mounted layout, with a large spacing between phases, fully meets the requirements of air clearance, thus achieving a narrow design. The width of 400/450mm greatly reduces the floor area, providing an advanced solution for urban power distribution of every inch of land and every inch of gold. It has obvious advantages for prefabricated switch stations, power distribution room renovation, and other areas. The three-in-one circuit breaker can also be made into a handcart structure as a whole, which can be extracted from the inside of the switchgear, providing convenience for maintenance and repair. The integrated handcart is extracted from the outside of the cabinet, and the valve plate automatically blocks the static contact on the busbar side, ensuring that the live body is not exposed when the compartment door is opened, ensuring safety and meeting the five prevention interlocking requirements

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