Can somebody please explain to me the purpose of the ring main unit? what is the
ID: 3348884 • Letter: C
Question
Can somebody please explain to me the purpose of the ring main unit? what is the ring main unit and how does it actually operate? also, are there ring main units found in primary substations too?
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Let us talk about some basics first,
Swithgears - A switchgear is basically a combination of circuit breakers that is used to protect or isolate the electric equipment is a power distribution system. It is characterized by the type of insulation it provides , air oil or gas.
Ring main units are type of switch gears that are factory assembled and used for medium level to low level voltage. Typically between 8kv to 32kv. Usually gas insulated RMU is used with SF6 gas.
Purpose - If i write in layman terms than RMUs are modern day equipment protectors that protect the electrical wiring from most basic threats like insects, moisture etc. to the most fatal threats like short circuits and other major faults. The main thing that a RMU protects is our distribution transformer because it is directly connected to all the major equipments.
Operation - Every switch in a RMU is of three position type i.e. open/close/earth.Now-a-days RMUs can be operated remotely using DAS/SCADA and can be directly controlled from the server room. Another very important advantage of RMU is its low maintenance cost because of the whole system is sealed and that it is very compact in size.
RMUs are not used in primary substations because it is not designed to withstand very high voltages. In primary substations we require very big switchgears with very high capacity.
Now you would ask me why not use it in secondary substation?
That is because its not economical and also not as handy as RMU. RMU is handy bacause of its compact size, remote operation etc. With the invention of RMU we have traded the operation capacity(Voltage rating) with the perks like compact size, low maintenance etc.
I hope i was helpful in clearing your doubts. :)