Distribution Transformers

Types

• Oil-immersed transformer — most common type, cooled by mineral oil. Used outdoors for substations and pole or plinth mounting.
• Dry-type (cast resin) transformer — no oil, so lower fire risk. Chosen for indoor use in buildings, hospitals and malls.
• Pole-mounted transformer — smaller ratings on a utility pole for rural and street supply.
• Pad- or plinth-mounted transformer — installed on the ground in a housing society, campus or factory.
• Amorphous core transformer — lower no-load losses for energy savings on lightly loaded transformers.

What to check before buying

• kVA rating, with a margin over the calculated load, and the primary and secondary voltages (for example 11 kV to 415 V).
• Energy efficiency level: BEE star rating or loss levels as per the applicable BIS standard.
• Vector group, cooling type, tap changer, impedance and temperature rise.
• Accessories: breather, Buchholz relay where applicable, oil level gauge, and protection fittings.
• Factory test reports, routine test certificates and inspection before dispatch.
• Warranty period, delivery and installation scope, and GST invoice. Check approval requirements of your electricity distribution company.

Who buys them

Factories, housing societies, hospitals, malls, campuses, contractors, solar developers and utilities.

Frequently asked questions

What kVA transformer do I need?

Add up the connected load, apply a diversity factor, and size for future growth. An electrical consultant or the utility can confirm the figure.

Oil-filled or dry-type?

Oil-filled costs less and suits outdoors. Dry-type is safer for enclosed spaces and basements where fire risk matters.

What are no-load and load losses?

They are the energy the transformer wastes when idle and when loaded. Lower losses reduce running costs over its life.