Transformer 22 to 11 k V

[maypot]

What are the technical constraints in converting one 12 MVA 22/6.6 k V ( Y Delta ) to 11/6.6 k V ( Y Delta ). We are redesigning our network and will be feeding through a 11 k V network instead. Hopefully if this conversion is feasible, there will be no need to purchase a new 11/6.6 k V transformer.

Bob

 

[RRaghunath]

May be you need to redesign the HV windings of the transformer, no. of turns, conductor cross section etal including tap windings.

Fitting the new windings in the same core assembly could be another issue.

The cooling will also be an issue as the 11kV, 12MVA winding carries more current than the 22kV one and the copper loss in the windings is likely to be higher and the cooling system may require augmentation as appropriate.

May be, an experienced transformer designer can provide more info on the subject.

 

[alehman]

Rewinding a transformer is a costly and time-consuming proposition. It may be more practical to purchase a new transf with the correct voltages, and sell this one if you can.

 

[prc]

What aleman said is correct .Most cases it may be cheaper to go for a new unit.Any way this option can also be considered ,if the manufacturer is nearer to you .

Another option is to go in for a 11/22 Kv auto transformer piggyriding to existing transformer.Auto trf will be cheaper than a 11/6.6 Kv trf .Disadvantage is additional loss in auto trf which of course will be less than a normal two winding trf.

What Raghunath expressed is a common misconception with electrical engineers -in transformer when current goes up copper loss will go up . Loss depends on only current density and not on the absolute current value . It never happens in trfs that losses are more in Lv wdg than Hv wdg ,but normally the reverse is true.