Thermodynamic equilibrium of transformer oil-paper insulation — An experimental study

Abstract

Formation of moisture is the main reason that reduces dielectric strength of oil paper insulation in a transformer. Paper insulated copper conductors in a transformer serve as the main source of moisture. Generation of heat in copper conductors initiates cellulosic break down and leads the formation of water in transformer. Moisture reduces the insulation strength mechanically, electrically and chemically. This initiates the growing importance of condition monitoring of oil and paper separately for a power transformer. Oil moisture in a transformer can be experimentally found out from Karl Fischer Titration method, but paper moisture is generally estimated from some well known formula and standard curves. But such estimation may lead to an ambiguous conclusion, because these values are highly depended on their thermodynamic equilibrium. Hence there is a serious need to find out the values of paper moisture independently. This paper provides experimental results of a comparative study between ways of accessing moisture content in oil and paper separately to conclude about the status of insulation in a transformer.