Matthiessen - EMILE HAEFELY & CO LTD Switzerland

Instrument Transformer should require a minimum of maintenance work during their operation time. This has to be taken into consideration when the apparatus is designed. Modern design concepts are available to meet this requirement. However there should be a posibility for diagnosis of the condition of the material after a certain period of operation to determine the further safe service time. This pater is discribing how minimum maintenance can be influenced by design, what service checks should be performed and what values of oil tests are acceptable or need further investigation.