Oil Containment Dimensions and safe distance between Power Transformers

Oil Containment Dimensions 

and 

safe distance between Power Transformers 

The effective volume of the oil containment shall be greater than or equal to the 110 per cent of the transformer oil. In case the oil containment is filled with gravel, the above percentage shall apply to the available volume of the containment (air pockets) for oil in case of an oil spillage. 

The volume of oil of a specific size transformer, might be different for different manufacturers. The BIL level can also affect the size of the tank and consequently the volume of transformer oil.

For a typical 20 MVA transformer with an Off-load tap changer,  the volume of oil  can be 5000 US Gallons or almost 19000 liters. 

Another important parameter in the design of the containment is the clearance between the transformer and containment wall. According to IEEE recommendation, the minimum horizontal distance of any oil contained part of the transformer and the containment wall would be 1.5 meters. 

Factory Mutual -the prominent insurer of industrial premises- is a good source for safty regulation and clearances and measure to mitigate the risk of hazards in heavy industrial projects including emergency generators, transformers and other station equipment.

Recommendations on the clearances of typical 20 MVA transformer would be as follows:

Between the transformer containment and a combustible wall: 25 feet (7.62 meters)

Between the transformer containment and a 2 hours fire-resistant wall: 15 feet (4.57 meters)

Between two transformers: 25 feet (7.62 meters) 

.

Note 1:  A brick wall is considered to be combustible and do not offer a 2 hours fire resistance.

Note 2: A fire wall would be required to install transformers closer to each other. Minimum distance between the transformer and the fire wall would be 1.5 meters.

Masoud Kashani

February 2014