Condition monitoring of power transformers by oil analysis techniques

Transformer faults are generally the result of long-term degradation of the oil-paper composite due to a combination of heat (pyrolysis), moisture (hydrolysis) and air (oxidation). Here, the author describes how dissolved gas analysis and Furfuraldehyde measurements are being used successfully at EA Technology in condition monitoring of power transformers following a series of experimental investigations. In this presentation, the results of some experimental investigations are discussed. The presentation also includes some results of recent accelerated ageing tests on 11 kV transformers. Top-oil temperature of 120°C and winding temperature of 200°C were reached in the final part of the ageing tests. Some particular features of the parameters involved in oil analysis, including Furfuraldehyde concentration, are discussed