“Draw a feeder distribution single line diagram with an 11 kV ring main unit, incoming and outgoing 630 A load-break switches, transformer VCB and protection CT, a 1000 kVA 11 kV/415 V transformer, and retail and office LV feeders.”
Read the decisions behind it.
Incoming and outgoing load-break switches preserve the 11 kV ring path.
A VCB and CT-protected relay protect the transformer branch.
A 1000 kVA transformer steps 11 kV down to 415 V.
Retail and office loads leave from individual protected feeders.
Use this for a commercial site supplied from an 11 kV ring network. The utility determines the ring operating policy and protection arrangement.
Other examples in this family.
Common questions
What is an RMU?
A ring main unit is compact medium-voltage switchgear used to connect and sectionalize a ring network.
Why is a VCB used for the transformer feeder?
It provides controlled interruption and protection for the transformer branch.
Can the ring remain energized during transformer maintenance?
Often yes, if the relevant switching procedure and utility operating rules permit it.