In power transformers and in electric equipment in general, oil is used for insulation of equipment and for cooling. Using certain types of oil for power systems is regulated by international and national legislation and standards. The purpose if to keep equipment and systems in good condition, which depends on some parameters and general condition of transformer oil.
Any business with uses oil is concerned with the issue of oil storage. This is especially important for the energy sector.
Transformer oil may come form the factory or substation in different condition: fresh from the manufacturer in possible increased water and gas content accumulated during transportation; oil purified after shipment and ready for operation; clean oil, filled into the equipment, compliant with specifications; used oil, removed from equipment after loss of functional properties; regeneratedused oil after physical, chemical or combined treatment with restoration of original specifications and ready for further use.
Transformer oil delivered from the manufacturer and purified as necessary to comply with the regulations, is stored in liquid storage tanks at oil facilities.
For the purposes of fire safety, the manufacturer must strictly adhere to the requirements of national standards. However, the actual method of storage, availability of specially equipped buildings, tanks and service equipment is variable.
A wide range of oil storage tanks is out in the market. There are soft tanks, which allow to drain and store oil quickly servicing and transformer downtime, but are more suited for reduction of automobile transportation of oil to interim storage facilities.
For actual storage of liquids, the most widely used are vertical cylindrical tanks, equipped with level and quality controls, agitation systems and temperature sensors and maintenance systems.
A vertical insulated tank is made of construction steel with heat carrier circulation pipes below the surface. For servicing, a ladder is mounted on the tank with protective rail along the top. Temperature is monitored by a thermistor installed in the bottom of the tank, which shows the temperature on the control panel. The heat exchange system is an array of pipes and insulation jackets.
Correct oil storage systems allow to keep the oil in good condition and preserve its specification, lowering the cost of additional purification and regeneration due to premature aging of the oil.