This article will focus on the characteristics of modern hydrocarbon transformer oil as it relates to current refining technologies being used to guarantee the highest quality finished products available and adherence to all ASTM 3487 standards. In a recent article in Transformer Technology, I presented the fact that refining methodologies used to refine current production hydrocarbon-based transformer fluids have improved greatly over the past number of years. All the major refiners of finished transformer oil stock have completed various degrees of refinery upgrades in terms of hydrotreating severity. The units in place today all meet the minimum standards of heat and pressure that can be used to reform their crude slates to varying degrees of finished quality. Some have significantly upgraded their vessels to produce very high-quality materials which far significantly exceed the minimum standards.
Although we hear much in the news and political sphere about the evils of the hydrocarbons which make our current life so enjoyable, the fact remains, many industries are inextricably linked to the use and dependence on hydrocarbons in various form for many years to come. It is true, new technologies and products have arisen to maybe one day replace conventional oil-based transformer fluid, but for the meantime and at least the foreseeable future, most large OEM substation and large power transformer manufacturers will continue to hydrocarbon-based products to fill their units.
In the standard grouping of ASTM 3487 tests used to prove the quality of current insulating oil acceptance, there are certain tests which speak directly to the improvement in oil refining technology. ASTM D2440 is one of them. ASTM D2440 is a standard test which measures an oil’s resistance to oxidation either in normal operating conditions or under more severe conditions, such as heat, vibration, shock loading, surge voltages or general high electrical stress. The chemical reactions to conditions inside the transformer can result in sludge build up and elevated acidity. Like most chemical reactions, heat is a major accelerator. Much of the severe decay of transformer oil can be and is prevented by regular testing of the oil inside the unit. Like a good doctor who orders regular blood work,