Abstract: State assessment provides the bases for power transformer maintenance. A new method to recognize the state of power transformer without the standard fault model is proposed. This method introduces the grey target theory into the state assessment of power transformer by regarding the fault system as a typical grey system. In combination with the technique of Dissolved Gases Analyses (DSA), the steps of the arithmetic for state assessment are given. In this arithmetic the equal weights of dissolved gases used in existing arithmetic are replaced by the variable weights, which are more approximate to the real state of power transformer in practice. The variable weights of dissolved gases are determined by the analysis method of grey contribution degree. Experiment results show that this method can be used to recognize the state of power transformer in the absence of standard fault model.

Key words: electrical engineering, power transformer, grey system, grey target theory, grey contributing degree theory, dissolved gases analysis, variable weights