Why should DBPC and DBP be monitored in transformer oil?
DBPC is short for 2,6-ditertiary-butyl paracresol and DBP is abbreviation for 2,6-ditertiary-butyl phenol.
The rate at which oxidation inhibitor levels in insulating oils become depleted is dependent upon several factors. The temperature of the oil, amount of oxygen contents, soluble contaminants in the oil, and catalytic agents in the oil. Some transformer manufactures do not furnish transformers with inhibited oil.
As the inhibitor content becomes exhausted, the rate of oxidation and the deterioration of the oil increases. By-products such as acids and sludge begin to form and attack the transformer's paper insulation system, which can lead to the loss of operating life. Oxidation inhibitor material can be replenished, insulating oil can be changed or serviced, but the paper insulation cannot be replaced, renewed, or restored. It is generally regarded that "The life of a transformers is in the life of the paper insulation".
Modern transformers are either sealed to exclude air and moisture or on larger transformers, they can be protected by an externally mounted gas system that provides an inert gas atmosphere. The benefits of keeping the oxidation inhibitor at an optimum level (0.3%) can help to extend a transformer's insulating oil over many years.
The oxidation inhibitor test is also suitable for manufacturing control and specification acceptance.
