By A Ring Main Unit Switchgear is a metal factory assembly that is considered one of the main components of ring main power distribution. It works on a medium voltage range, from 7.2 kV to 36 kV, and ensures that electric current has a reliable and steady flow. It supplies electricity to homes, industries, and business departments with enhanced security that helps in breakdowns during any emergency or disturbance in the system.
This ring-type network is used to supply electric current through two directions even if one point has very slow potential. The United Kingdom was the first country to introduce the Ring Main Unit, and now it is available in different countries with a high material to get a longer life.
Major components of (RMU) Ring Main Unit Switchgear
The main part of the ring main power distributor consists of the following components:
1. Two main switches
These switches are connected to the main ring unit and supply power from both ends or a single end when there is one out.
2. Circuit breaker
The circuit breaker is connected to the distribution transformer that is used to step down the voltage when it is required.
3. Cable connections
These cables help in connecting the ring main unit with the transformer.
4. Relay
Fault indicators, an ammeter, and protective relays are included.
5. Enclosure
It secures the insulation and protects the internal parts of the system.
6. Fusible switch
It can be operated automatically or manually according to the design and protect the transformer from faults.
Types of Ring Main Unit Switchgear
Following are the types of Main Ring Unit
Air-Insulated RMU
In this type of RMU, air is used as an insulating medium, and it requires more maintenance and space.
Gas-Insulated RMU
It is a compact gas RMU that requires very low maintenance. It uses sulfur hexafluoride (SF6) gas in the insulation medium. These ring mains are used in industrial zones, urban substations, and outdoor installations.
Oil-insulated RMU
It uses arc-quenching and oil as an insulation medium, and it is known as the best insulation. However, the oil insulation RMU can cause oil leakage and higher fire risks.
What are the advantages of the Ring Main Unit Switchgear?
- It supplies current to the whole ring distributor without any interruption.
- It has a compact design that is suitable for lower spaces.
- Requiring very low maintenance, especially in the gas insulation RMU.
- In the smart grid system, it is monitored automatically.