Submersible pit type transformers


Prestige and Reliability

These transformers can be installed in underground chambers or pits where there is flooding risk, as it has been foreseen that they may remain submerged in water. They are completely airtight, bathed in mineral oil, without conservator and have a dry nitrogen upper chamber to absorb oil expansion. The medium voltage external connection is made with plug-in connectors on-load operated, with control-rod. All the external surface of the machine has a bituminous-epoxy paint protection.


These transformers are manufactured according to IEC 76 and additional standards. Among their main features we can mention:
High Voltage side: 13,2 kV
Low Voltaje side: 0,4 – 0,231 kV
Available powers: 200, 500, 630, 800 y 1000 kVA
Regulation: ± 2 x 2,5 % on High Side Voltage
For other Voltages and Powers, contact our representative

Design and manufacturing

They are fully watertight in order to preserve the insulating oil. A dry nitrogen upper chamber keeps a light overpressure when the oil is at its minimum temperature.

This transformer side is protected by limiting fuses located in their respective holders.

It is built with steel sheets and can withstand an internal overpressure of 0,5daN/cm2. Two supporting U-beams are welded at the baseline in order to ensure a minimum distance of 50 mm to the floor.

It is built with steel sheets and designed in such a way that permits to disassemble the transformer by lifting the active part solidly linked to it. To ensure watertightness, the cover is welded to the tank.

Placed on the transformer cover, they include:

  • Off-load five position tap-changer, ± 2 x 2,5%
  • Elastimold-type M.V. terminal bushings for dry-insulation conductors.
  • L.V. terminal bushings, consisting of an epoxy resin insulated copper bar, which composes the fixing unit.
  • Grounding clamps
  • Fuseholder board
  • Limiting fuses (placed inside the holders and accessible from outside)
  • Oil level gauge.
  • Sample extraction valves.
  • Filling valve.
  • Thermometer case.
  • Manometer for internal overpressure control.
  • Pneumatic valve for Nitrogen injection and outlet.
  • Safety valve to prevent an excessive Nitrogen overpressure.
  • Tests.


– Dimensional testing.
– Measuring of winding resistance
– Measuring of transformation and phase relation.
– Shortcircuit Test.
– Vacuum Test.
– Dielectric Test.
– Airtightness Test and safety valve and tap-changer test.


  • Heating Test
  • Airtightness Test.
  • Impulse Test.
  • Oil Test.
  • Tap-changer type Test.


Description Sizes (mm) Weight
Length Width   Heigth
200 KVA, 13,2/0,4 – 0,231 KV 1650 1100 1450 1470
500 KVA, 13,2/0,4 – 0,231 KV 1650 1100 1550 2320
630 KVA, 13,2/0,4 – 0,231 KV 1700 1100 1600 2800
800 KVA, 13,2/0,4 – 0,231 KV 1700 1150 1600 3800
1000 KVA, 13,2/0,4 – 0,231 KV 1800 1200 1600 3910