Difference between VCB and RMU

Almost entirely unrelated, nor well described.

Then do the research and let us know what you discover.

Its not the amount of cable that goes in and out an electrical device which describes best its use and function thats for sure.

So keep looking.

do you have idea of the exact use and working of rmu..

To feed a transformer with a ring feeder.

"do you have idea of the exact use and working of rmu.."

I hope so, I have to operate them.

Not blown myself up yet.

Honestly I don't. But if I was to work in that field I would find out.

I'd start with an internet research, but buying a reference book would be making sense to get in-depth knowledge.

http://lmgtfy.com/?q=Difference+between+a+Vacuum+Circuit+Breaker+and+a+Ring+Main+Unit

See: Schneider Ring Main Unit and ABB VD4 Vacuum Circuit-breaker -for instance.

Why are you curious about them ... Hopefully you are not going to experiment. Coz honestly if you were an Electrical person you wouldnt be asking such stuff. Next time you will want to know about transformer them What happens if you connect 33kV on 415V .... Boom! then we wont hear from you nor see your posts again coz you will be roasted...

Ring main unit is mostly adopted in modern power systems. It has two switches. The main difference is, RMU's are limited to lower ampere ratings of 630A or 1250A and fault rating/ operational flexibility. A circuit breaker, or fuse-switch can be connected between the two ring switches. These CB controles spur circuit or local transformer.

RMU is allow to install on medium voltage distribution network and mostly used work locally is main advantage particularly where limited panel space. It’s a fully automatic linking system. An Operation is only possible in case door is totally closed. Vacuum Circuit breaker with disconnecting switch. Circuit breakers operate automatically, triggered by electromechanical mechanism inside and are a safety feature for abnormal loads and voltages in the circuit.