Hi everyone. I'm reading about RMUs ( ring main units), and I encountered this sentence "It is basically used as an uninterrupted power supply. Alongside, it also protects the secondary side of the transformer from occasional transient currents". First of all, what does "it works as an uninterrupted power supply" mean?? secondly, how does it protect the transform secondary side from transient currents while it's connected to the primary winding of the transformer?!!!