Experimental Investigations of Mechanical and Chemical Properties of PVP Precompressed Pressboard Insulation for HV Power Transformers

As the rating of power transformers increases, oil–paper insulation requirements become extremely difficult as insulation system should have more withstanding capabilities of high voltages and high reliability. Thus, it is important to find pressboards and precompressed pressboards using new insulating polymers with acceptable mechanical, chemical and electrical insulation properties that can used as an insulation barrier for high voltage–power transformers. The cellulose material-based pressboards are in great demand for high voltage–power transformers. Many researchers have investigated pressboards prepared from kraft pulp and found suitable in solid insulation of power transformers since decades. Pressboards are usually compressed with water soluble and insoluble polymer resins to develop precompressed pressboards. Water soluble insulating polymer resigns precompressed pressboards are of great importance, since they are recyclable. This paper mainly focuses on preparation of precompressed pressboards using a closed ring water soluble insulating polymer polyvinylpyrrolidone (PVP) and in order to ensure a correct functioning of this insulation in transformers, it is very important to characterize the mechanical and chemical properties of precompressed pressboards. These properties have been studied, and the results are compared with precompressed pressboard prepared from polyvinyl alcohol (PVA). It is observed that mechanical and chemical properties of PVP precompressed pressboards have shown substantial improvement compared to PVA precompressed pressboards.