What is Ring Main Unit (RMU) and its function in a solar project?
A standard piece of switchgear in distribution systems comprising of switches for switching power cable rings and of switches in series with fuses for the protection of distrbution transformers. RMU: Ring Main Unit. RMU used for H.T.side. RMU is having
3no.s of switches(Circuit Breakers or Isolators or LBS), it
is used for two inputs with mechanical or electrical
interlock and one outgoing to the load. Either one input
with two outgoings. RMU used for redundancy feeder’s
Ring main unit is used in a secondary distribution system. It is basically used for an uninterrupted power supply. Alongside, it also protects your secondary side transformer from the occasional transient currents. Depending on your applications and loading conditons you can use a swicth fuse combination or a circuit breaker to protect the transformer. This transformer connected to the switch fuse/ circuit breaker is called your T off. In a common arrangement you have Load break swicthes on both the sides of your T off. Ring main Units come in standard ratings of
11/22/33 kV, 630/1250 A, 21 KA/3 secs.