Component composition of ring mainunit:

Ring main unit (RMU) is a group of electrical equipment that high-voltage switchgear is installed in the steel plate metal cabinet or assembled into a bay type RMU. The core part of RMU is load switch and fuse

Each ring main unit has 3 to 5 main switch boxes, so the flexible connection mode can meet the power supply demand of different power distribution network nodes

Since the power switch device and the hard bus are enclosed in the same closed metal shell, SF6 gas is generally used as the insulation and arc extinguishing medium. The switch adopts three-phase linkage three position load switch or circuit breaker, and the high-performance spring mechanism can realize fast switching operation

A single ring network unit is composed of different modules such as incoming line unit, measurement unit, TV unit and bus unit, and can arbitrarily combine various schemes according to actual needs

Classification of ring main unit:

Ring main unit is generally divided into air insulation and sulfur hexafluoride insulation. The function of ring main unit is to open and close load current, break short-circuit current and transformer no-load current. Ring main unit can charge current of overhead line and cable line within a certain distance, so as to control and protect the line. It is an important switchgear for ring main unit and terminal unit

In the cabinet, there are three types of load switches with air insulation: gas generation type, compressed air type and vacuum type. The load switch with SF6 insulation is SF6 type

The load switch in ring main unit generally requires three working positions, that is, cut off the load, isolate the circuit, and can be reliably grounded

Gas producing, compressed and SF6 type load switches are easy to realize three working positions, while vacuum type load switches can only be turned off and cannot be isolated

Therefore, the general vacuum load ring network switchgear in front of the load switch and an isolating switch to form an isolating fracture.
Characteristics of ring main unit:

1) Ring main unit adopts fully insulated and sealed structure, even can adapt to any outdoor environment

2) Due to the compact arrangement of the components in the ring main unit, the ring main unit is usually small in volume, light in weight and small in occupied area, which is conducive to improving the land use efficiency

3) Compared with other electrical equipment, the composition of ring main unit is simple, easy to install, and the maintenance workload is small

4) The visible fracture of the equipment can quickly and accurately confirm the contact position of the switch and ensure the safety of the operation and maintenance staff

Based on the above advantages, 10kV ring main unit is widely used in distribution stations and box type substations of load centers such as urban residential quarters, high-rise buildings, large public buildings, factories and enterprises