As you might understand before, RMU or ring main unit is a gas-insulated, sealed compact switchgear unit.
The main switching devices could be either:
Ring Main Units is utilized in a secondary distribution system.
It's utilized basically for an uninterrupted power supply.
It also safeguards your secondary side transformer from the recurrent transient currents.
Depending on your loading conditions and applications, you can utilize a:
That transformer linked to the circuit breaker or switch fuse is referred to as Tee off.
In a typical arrangement, you got load break switches on both sides of your Tee off.
RMUs are composed of incomer feeder and outgoing feeder.
The incomer feeder is either SF6 or vacuum circuit breaker with associated earth switch and disconnect switch.
You see;
The incomer feeder is provided with the delivery protruding from the enclosure of RMU for supply cable connection.
On the other hand;
The outgoing feeder is composed of load break switches along with:
Provision for cable connection is given in outgoing feeder.
Aside from that:
The load break switch is only an isolator that can break the circuit through on load situation.
The incomer and outgoing feeders are covered in an SF6 setting to make the entire design compact.
Its compatible instrument for tracking of SF6 gas pressure is installed on the RMU.
The scale of this device is categorized into three or more subscales for various temperatures.
What's more, every subscale has a red and green colored zone.
For a specific temperature, you must refer the necessary subscale and gas pressure.
That's because it should be in the green colored zone.
Mechanical indicators are presented on the panel for the status of:
Current transformer of the desired ratio is set up in the incomer feeder.
The secondary of that is linked to a self-powered relay for needed protection.
You see;
A self-powered connection device is also installed on the RMU.
That relay is microprocessor-based numerical rely on upon along with user interface.
That relay offers limited protection like:
Even though the various manufacturer provides a various set of protection, some manufacturer might provide protection according to the specification of the user.
Within the distribution system, Ring Main Unit is widely utilized.
That's because it is a total package.
It only requires a cable connection and installation.
Everything else is in the package.
That massively lowers the commissioning period.
RMUs are utilized in underground cable distribution network at the:
Furthermore,
RMUs are also ideal for use in the following applications:
There's no doubt, the ring main unit is the only solution that is filled with wide-ranging capabilities.