The installation requirements of open-air and semi-open-air transformers are as follows:

1) The ordinary transformer installed near the exterior wall of the building should not be located on the low side of the inclined roof to prevent the roof ice or water from falling on the transformer.

2) 10 (6) kV transformer should be surrounded by fixed fences (or walls) not less than 1.7m. The net distance between transformer outline and fence (or wall) should not be less than 0.8m, and the distance between transformer bottom and ground should not be less than 0.3m. The net distance between adjacent transformers should not be less than 1.5m.

3) The fireproof net distance of adjacent flammable oil-immersed transformers supplying primary load with electricity or oil over 2500kg should not be less than 5.0m. Otherwise, a fireproof wall should be set up. The wall should be higher than the top of the oil pillow and its length should be greater than 0.5m on both sides of the oil-retaining facilities.

4) When the outer wall of the building is less than 5 meters away from the outer surface of the outdoor combustible oil-immersed transformer, there should be no doors, windows or ventilation holes in the outer wall of the building when the oil volume of the transformer is less than 1,000 kg and 3 m [10(6) kV] is added below the horizontal line and both sides of the transformer above 3 meters. When the distance between the outer wall of a building and the outer surface of a transformer is 5-10 m, a fire door can be installed on the outer wall and a non-combustible fixed window can be installed above the transformer height.

5) When the oil quantity is more than 1000kg, the oil storage tank which can hold 100% oil or 20% oil storage tank or oil retaining wall should be set up.

When a reservoir or oil retaining wall containing 20% oil is installed, the oil should be discharged to a safe place without causing pollution hazards. When there is a total accident oil storage tank with oil and water separation, its capacity should not be less than 60% of the oil volume of the largest transformer.

The length and width of oil storage tank or oil retaining wall are generally 1 m larger than the outer dimensions of transformer. The surrounding area of the oil storage tank should be 100 mm above the ground to prevent rainwater and sediment from flowing into the tank. In general, the oil storage tank is paved with pebble layer with thickness not less than 250 mm, and the diameter of pebble is 50-80 mm.