Why is a delta system preferred?

[kpitsmpl]

In ungrounded delta systems high transient over voltages can occur and it's difficult to locate a fault. What are the other benefits besides being able to operate with a single fault?

On another note, I have a 5kV switchgear fed from a 27.6-4.16kV, 2MVA transformer and equiped with bus PTs and CTs and 750 Multilin for protection. Is it possible to use this bus PTs and CTs to infer the voltage and current on the 27.6kV bus and feed it into the same or another Multilin?

Kevin

 

[davidbeach]

A delta winding is not necessary to run ungrounded, you can leave a wye ungrounded and it will perform similarly to an ungrounded delta.

If the 27.6kV-4.16kV transformer is a grounded-wye / grounded-wye transformer the secondary voltage can be scaled to provide a representation of the primary voltage, that's what VTs do. Any other connection though (including leaving either side ungrounded) and you will have some errors. If the power transformer is wye / delta (wye side grounded or ungrounded) you will have the least information about the high side, and if either side is a delta you will not have any V0 information about the high side. Best to have VTs where you want to know the voltage.