Thanks to economical conditions in power system in last few years, the life management and estimation of the remaining service life of power transformers get more and more attention. We have to know what is present state of paper-oil insulation (or better trend of state) for it beside knowledge of transformers history and operating conditions (temperature, loading). One from the methods for judgement of insulation state is recovery voltage method. We had used this method successfully for verification of effectiveness of drying process in the past and for verification of quality of revision and repair works - in (15). In this paper we try to show the possibilities and limits of this method in estimating of ageing degree of power transformers insulation in service conditions by comparing the results of RV measurements with the results of degree of polymerisation of the paper sample.
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