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The difference between cable branch box and ring main unit

The key function of the cable branch box is to split or switch cables. Cable breakout. Carrying multiple small total area cables on a route with a long distance usually leads to extravagance and waste of cable application, so in the out-of-bounds to the power load, the main pole and large cables are usually used out-of-bounds. A wooden cabinet for cable distribution or transfer, divided into X in and X out, for load distribution or long cable transfer.
Ring main unit: cable distribution box with switch can be remotely operated. Switching station: small and medium-sized unmanned distribution station with single busway or single bus connection by section

Cable branch boxes are generally used outdoors. With the development of technology, cable branch boxes with switches are also continuously improved, and cables in large cities usually use a dual-circuit power supply method, so many people immediately call them the branch box with switch. It is an outdoor ring main unit, but most of the ring main unit at this stage cannot maintain distribution automation.

1. The components of the ring main unit:
Ring main unit also known as the enterprise of the ring network power supply system, is a group of high-voltage circuit breaker machinery and equipment installed in the thick steel plate metal material cabinet body or electrical equipment made into the assembly spacing ring network power supply system module, some of which use load switches and high voltage fuses. Each ring main unit is provided with a flexible connection method of 3 to 5 total bottom boxes, in order to consider the power supply system requirements of different power engineering distribution network nodes. Because the main power switch equipment and the hard busbar are encapsulated in the same closed metal casing, they are generally used as insulating layers and arc extinguishing materials. The snap-yellow tissue can keep the switch running quickly. An independent ring network module is composed of different control modules and busway modules such as three-phase five-wire enterprises, quantity units, TV enterprises, etc., and can form various different schemes at will according to actual needs.

2. the classification of ring main unit:


Ring main unit can be divided into four types:

a. Vacuum pump type ring main unit: Vacuum pump type ring main unit is a new generation of green environmental protection solid insulation layer vacuum pump ring main unit product. This product uses vacuum circuit breaker + microcomputer protection device, and all conductive circuits use epoxy resin glue or silica gel. The encapsulation ensures a high safety factor in operation and actual operation, and the rated voltage of the application can reach up to 24KV.
b. SF6 ring main unit: SF6 ring main unit is a kind of high-voltage household appliances with gas insulation layer or vapor insulation layer with load switch as the key component, which can be easily composed of multi-circuit access, conversion, connection and maintenance of power supply system. Make up machinery. Its main circuit key components are composed of SF6 load switch or additional isolating switch and other auxiliary tools and household appliances.
c. Gas-generating ring main unit: The gas-generating ring main unit is made of solid gas-producing raw materials (such as plexiglass plates) to make arc extinguishing components. The gas-producing raw material is transformed into a gas, which cools the electric water and blows it out. The larger the amount of split and combined current, the stronger the electric isolation, the larger the converted gas, and the higher the actual effect of arc extinguishing.
d. Compressed air ring main unit: The compressed air ring main unit is named after the selection of the compressed air load switch. The compressed air switch uses air compression to blow the arc. When it is pulled in, the compressed air piston rod moves rapidly, and the high pressure gas in the cylinder is blown out to the electric isolation through the nozzle when the arc extinguishing circuit breaker is separated to cause the electric isolation Make the electric solitary longer and blow it out when the current is lower. Generally, the current of the compressed air load switch is about 1 kA, so that the breaking and short-circuit capacity of 50 kA can be achieved. The thermal stable current is generally 20 kA, 3s.

3. What are the structural characteristics of the ring network cabinet?
a. The ring network cabinet is composed of four parts: the switch room, the high-voltage fuse room, the operating organization room and the cable room (plate spring).
b. The switch room is composed of each active circuit (including grounding device switch and load switch) sealed in the metal material casing and the busbar between the circuits. The cover is welded by electric welding of 3mm cold-rolled plate (or thick steel plate without embroidery). Each action circuit contains a load switch and a grounding switch. The load switch is composed of the moving circuit breaker system software for vertical fitness movement and the static contact located at the lower web end. When the switch is reclosed, the moving circuit breaker moves downward and the load switch is connected. The grounding device switch is composed of a movable contact knife and a static contact knife. During the whole process of the bouncing yellow fitness exercise, the grounding device switch is quickly connected. There are 4 square machining process holes on the top and back of the switch room, and the reverse side of the ring main unit is equipped with a viewing window, and the “dividing” and “closing” parts of the grounding device switch can be seen. The rear side of the ring main unit is equipped with explosion-proof equipment.
c. The load switch adopts the compressed air blowing structure, which has strong arc extinguishing ability and does not harm the two colors and the insulating layer to the ground. Both the dynamic and static contacts contain arc circuit breakers, which further improves the breaking frequency.
d. The high-voltage fuse and the load switch room form a transformer maintenance circuit. The high-voltage fuse is installed in an epoxy resin-cast insulating cover. After the high-voltage fuse is blown, the striker pops out and the load switch is closed.
e. The operating organization room is located on the opposite side of the ring main unit. In each action circuit, the load switch is equipped with a human resource (or electric) energy storage technology spring operating organization, and the grounding device switch is equipped with a human resource energy storage technology spring. Yellow operating organization, the control panel has openings for actual operation of load switch reclosing and manual pull-in rotary button and grounding device switch, and actual operation holes for reclosing, load switch opening and reclosing position display lights and electric type Open and reclose buttons, and set up simulation simulation line, switch status display screen and locking part, the actual operation of load switch and grounding device switch is equipped with interlocking equipment to avoid operation errors

Post time: Sep-02-2022