RMU and switchgear

[Mefi01]

Hello friends,

could someone please explain the main difference between a ring main unit and MV switchgear. in a substation do we have to have the two?

 

[ScottyUK]

Switchgear is a fairly generic term for equipment which incorporates switches or circuit breakers.

An RMU is a specific type of switchgear comprising a pair of switches for a ring circuit to loop in and out, plus a switch-fuse or breaker for the tap-off feeding the load, all integrated into a single unit.

 

[vijaypandiyan]

In MV switchgear, you can have incomings and outgoings as per load. But in RMU it is mainly two incomings+1 outgoing so that your outgoing power is not disturbed.

Thanks,
Vijay

 

[krisys]

But, RMUs with multiple feeders are also available in the market. This is a variation of the basic RMU.

RMUs are mostly suitable for outdoor installation with minimum protection and controls. In some cases even the external control supply also not use.

 

[vijaypandiyan]

Agree with Krisys.
Maybe you can check ABB Safeplus for more details.

Thanks,
Vijay

 

[Padlock01]

I am currently using Schneider 12kV RMU's in Minisubs (630A Isolator/200A Breaker/200A Breaker) and as a Main 11kV Switchboard 20kA we find its a cheaper option than the withdrawable
type. One can add features such as standoff trip/close facility. The VIP410E protection relay has adequate settings.

 

[krisys]

For the Schneider Make RMUs, you don't need a separate control power supply. It uses the self powered release mechanism. This is a specific advantage, when it comes to the remote area, where providing a dedicated control power supply is a problem.