Selection of Isolation Transformer 80 KVA 3 Phase

• Voltage
• Size
• Weight
• Mounting arrangement detail
• Lifting arrangements
• Termination detail
• Circuit protection detail
• Earthing detail
• Ingress protection detail
• Ambient temperature/pressure/climatic conditions
• Shipping and delivery detail
• Standardisation compatibility for spares and servicing
• Colour
• Noise

to name a few.

Also applicable electrical standards the transformer is built and tested to.

Warranty.

Cost.

If you are lucky you can buy a pre-built product, if not (or you have special requirements) then you will need to get a transformer company to manufacture one.

I think this is in continuation of your earlier thread. If so, in addition to other specs already pointed out, you will have to specify vector grouping and delta/ star configuration. If sensitive equipments are connected down stream, you may also consider to include additional earth shield for the isolation transformer. Also depending on where you propose to locate the transformer, you have to specify whether oil or air cooled ( natural or forced ) type. The cable entry points will determine whether you want system built to take top or bottom entries of cables. Neutral point terminal and conductor to be designed for 2 times the rating of phase conductors. Also power control MCCB's for both incoming & outgoing side to be included, either integrated into the unit or as standalone units.