Power and distribution transformers are some of the most important and expensive assets in a power network. Compared to other equipment, they are very reliable and require very little maintenance since they have no continuously moving parts. However, the insulating materials, being organic, degrade with time in service, and ultimately determine the end of life of the transformer.
In a poorly maintained free breathing transformer water can enter through the natural expansion and contraction of oil as the temperature cycles, but also water is a by-product of the breakdown of the long chain hydro- carbon glucose molecule, as a result of thermal and electrical stress. This leads to degradation of the organic insulation materials as the transformer ages.
2 x CL3A under test at the factory
Excessive moisture will saturate the insulation and increase its conductivity. At higher temperatures vapour or free moisture can develop increasing the risk of partial discharge.
TRANSEC is an on-line molecular sieve, developed and manufactured in the U.K. that is designed to continuously remove water from the insulating oil of a power transformer. As the ppm level in the oil is reduced, water from the solid insulation (where over 95% of the water will accumulate) will migrate from the insulation into the oil to redress the natural equilibrium. This process not only reduces ageing, but will improve the dielectric strength of the insulation, and increase reliability.