COMPARATIVE INVESTIGATIONS ON BREAKDOWN VOLTAGE OF PVA AND PVP PRECOMPRESSED PRESSBOARDS USED IN HV POWER TRANSFORMERS- AN EXPERIMENTAL APPROACH

The most significant characteristics of high voltage power transformers are capability to withstand breakdown voltage through faults in insulation system. Dielectric breakdown cause degradation of insulation system and study of its performance can give useful data regarding the condition of insulation. In this paper, the experimental investigations on Breakdown voltage were carried out at various temperatures on different thickness of laminated precompressed pressboards prepared by an insulating polymers polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). A test were conducted on a transformer model insulation comprising of precompressed pressboards impregnated with transformer oil kept between electric field electrodes arrangement for its behavior for high voltage applications. A variable high voltage AC were applied to test samples until breakdown occurs in the form of puncture and the readings were recorded. Investigations were done for different thickness samples at various temperatures and the results obtained shows superiority of PVP over PVA precompressed pressboards in regards to withstanding the breakdown voltage.