Ring Main Units 12kv Indoor Medium Voltage Switchgear , Gis Gas Insulated Switchgear

Ring Main Units 12KV Indoor Gas - Insulated Metal - Enclosed Switchgear

Overview

The switchgear is a kind of composite apparatus which seals all main circuits in a metal enclosure and take SF6 gas as arc extinguishing and insulation medium. It is suitable for ring network power supply and double radiates power supply in 10kV MV power supply network. It is also used in terminal power supply. Due to the use of ring network power supply increases the reliability of power supply, it is specially used in mineral plants, residence area, schools, parks, and so on for power distribution and controlling. In addition, because of its convenient connection and installation, small volume, it is also used in the substation as high voltage equipment on primary side.

Structure and Principle

RMU generally consists of three compartments. (If necessary, it can also be made to have one compartment, two compartments, three compartments or more, and it can also be combined by the expansion bus bar). Primary elements are located in a enclosed enclosure which is welded by stainless steel plate with a thickness of 3mm. Inside the enclosure, there is SF6 gas with a pressure of 0.04Mpa, which is used as the medium for arc-extinguishing and insulation. The gas pressure inside the gas-filled enclosure is monitored by pressure gauge. Apart from the gas-filled enclosure, other parts of enclosure are used for the installation and fixing of gas-filled enclosure. Those components which are not inside the gas –filled enclosure are located or installed inside this cabinet. This part of the cabinet is made by high-quality zinc steel plate coated with aluminum, which is bended by digital-controlled sheet-metal processing equipment and connected by high strength bolts and nuts. The door of the cabinet is made by high-quality bended and finished by plastic spray or spry coating.

1. RMU is made up of gas tank, mechanism compartment, cable compartment, instrument compartment, expansion bus bar, and so on. At the back of the gas tank, there is an explosion-proof device (not shown in the picture). When the internal arc pressure is too large, the high pressure gas inside the tank will be released from the back of the cabinet through the explosion proof device, which avoids doing harm to the operators.

2. The structure of the load switch is arc chute type, with strong ability of arc extinguishing.

3. The fuse and load switch room form the protection circuit of the transformer. The HV current limiting fuse is installed in the epoxy resin casting insulating enclosure. When the fuse burns out, the firing pin pops up and the load switch opens.

4. Mechanism compartment is on the front of the RMU. In every function circuit, load and circuit breaker are all equipped with manual (or motor) charging spring control mechanism, and three-position disconnector and earth switch are equipped with manual charging spring control mechanism. There is switch state indicator. Three-position disconnector and earth switch operation mechanism are fitted with padlock which can be used to prevent misoperation of unauthorized personnel when the equipment is not in operation. There is “five protection” interlock device in the operation of load switch——earth-switch——the door of cable room , circuit breaker——three-position disconnector——the door of cable room .