Transformer Oil Analysis

It is well known that regular oil analysis is extremely useful in monitoring the condition of engines , drivetrains, hydraulics, turbines and many other types of oil lubricated equipment. The same can be said for transformer oils which are used to insulate many transformers and other electrical distribution equipment. The analysis of transformer oils not only provides information about the oil, but also enables the detection of other potential problems, including contact arcing, ageing insulating paper and other latent faults and is an indispensable part of a cost efficient electrical maintenance programme.

Transformer maintenance has evolved over the past 20 years from a necessary item of expenditure to a strategic tool in the management of electrical transmission and distribution networks. Extreme reliability is demanded of electric power distribution and, even though the failure risk of a transformer and other oil-filled electrical equipment is small, when failures occur they inevitably lead to high repair costs, long downtime and very real safety risks. Moreover, transformers are too expensive to replace regularly and must be properly maintained to maximise their life expectancy.

However, breakdown of one of the most crucial elements, the oil / paper insulating system, can only reliably be detected by routine oil analysis. By measuring certain physical and chemical properties of the oil, in addition to the concentrations of certain dissolved gases, a number of problem conditions associated with either the oil or the transformer can be determined.  The following are some of the common tests performed on transformer oils:

Moisture Content

One of the most important functions of transformer oil is to provide electrical insulation. Any increase in moisture content can reduce the insulating properties of the oil, which may result in dielectric breakdown.  Water and oil, due to their differing chemical properties are not mutually soluble.