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Oil-Immersed Transformers

S11 / S13 / SH15 hermetically sealed and conservator-type distribution transformers, 10–35 kV, 100–4,000 kVA.

Copper foil windings of an oil-immersed distribution transformer

Oil-immersed distribution transformers

Oil-immersed transformers remain the workhorse of outdoor distribution: the lowest losses and cost per kVA, the best overload tolerance and a 30-year service life when correctly specified. MARS manufactures three-phase S11, S13 and amorphous-core SH15 series units from 100 to 4,000 kVA at 10, 11, 13.8, 20, 22, 33 and 35 kV, in hermetically sealed corrugated-tank or conservator designs, with copper or aluminium windings and off-circuit or on-load tap changers.

Construction

  • Cold-rolled grain-oriented silicon steel or amorphous alloy core, step-lap mitred joints for low no-load loss and noise.
  • Oxygen-free copper foil LV and layer-wound HV coils, vapour-phase dried and oil-impregnated under vacuum.
  • Corrugated tank panels for self-cooling (ONAN); radiators and fans (ONAF) for larger units.
  • Fittings: oil level gauge, dial thermometer, pressure relief device, Buchholz relay (conservator type), earthing terminals, bi-directional rollers.

Every unit is routine-tested to IEC 60076-1 — ratio, winding resistance, losses, applied and induced voltage, insulation resistance and oil dielectric strength. See oil-immersed vs dry-type and our guide to losses and total cost of ownership.

FAQ: Oil-Immersed Transformers

Hermetically sealed or conservator type — which should I choose?

Sealed corrugated-tank units up to about 2,500 kVA are maintenance-free because the oil never contacts air; they suit distribution networks and remote sites. Conservator-type units allow oil sampling and Buchholz protection and are preferred for larger ratings and utility substations where condition monitoring matters.

Can you supply 60 Hz oil-immersed transformers?

Yes. 60 Hz units for the Americas, the Gulf, the Philippines and Korea are designed with a different core section and flux density; a 50 Hz unit should not be used on a 60 Hz network without checking, and vice versa.

What losses do MARS oil-immersed transformers achieve?

S11 units meet standard IEC/GB loss levels; S13 and amorphous SH15 designs cut no-load loss by roughly 30 % and 70 % respectively. We quote guaranteed no-load and load losses on every offer so buyers can capitalise them.

Do you ship transformers oil-filled?

Units up to about 2,500 kVA ship oil-filled and sealed. Larger units may ship with a nitrogen blanket and oil in drums; impact recorders are fitted on request.