New Approach in Insulation System of Power Transformers – Insulating Oils with Less Impact on the Environment

Abstract

Paper    deals    with    comparison    of    selected properties of several vegetable oil representatives(commercially  available  ENVIROTEMP®  FR3TM  vegetable-based   transformer   oil,   sunflower   oil,   rape   oil   and   refined sunflower  and  rape  oil)  along  their  accelerated  thermal  ageing at  the  temperature  of  90  °C.  These  properties  are  compared  to two    widely    used    and    commercially    available    mineral transformer   oils   (Technol   Y   3000   and   Shell   Diala   DX). Combined  insulating  system  (oil-paper  system)  was  created with  the  usage  of  mentioned  oils  for  measurement  purposes. Dissipation   factor,   capacity   and   volume   resistance   are   the characteristics  measured  along  the  thermal  ageing  of  the  oil-paper systems. Infrared spectroscopy was used as the additional method. After 1000 hours of ageing, the dissipation factor of all systems  based  on  vegetable  oils  did  not  exceed  the  value  of 0,015. The volume resistance of systems containing mineral oils was  approx.  twice  as  high  as  volume  resistance  of  those  with vegetable oils. Capacity on the other hand was slightly lower in the  case  of  mineral  oils  application.  Experiment  also  showed that paper combined with vegetable oil dries more quickly than in  combination  with  mineral  oil.  Infrared  spectroscopy  has  not shown  any  expressive  changes  in  the  chemical  structure  of  all tested  oils  yet.  It  was  proven  that  all  monitored  electrical properties  of  commercially  available  ENVIROTEMP®  FR3TMtransformer  oil  are  very  similar  to  the  properties  of  common rape oil.