In this paper the performance of a new transformer diagnosis method is tested experimentally, The method is called model-based diagnosis because the diagnosis is based on an identified model of the component - the transfer function. Two test series are carried out to evaluate the method on transformers, a sensitivity test series and an ageing test series. The purpose of the sensitivity test series is to determine how close the identified transformer model is connected to the physical condition of the modelled transformer. The purpose of the ageing test series is to determine if it is possible to identify a development in the transfer function of the transformer towards breakdown. Based on the two test series it is concluded that the detection of failures and ageing phenomena in transformers by transfer functions is dependent on detectable changes in relatively few characteristic transformer parameters - basically lumped winding capacitances, total losses and core reluctance.
