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Low-frequency demagnetization for power transformers based on modified J-A model

This paper proposes a low-frequency demagnetization method based on multi-objective optimization. The multi-objective problem on demagnetization can be solved by linear-weighted-sum method. Where, the weight coefficients can be calculated by an allocation method based on the polymerization degree of each objective function. For a 127 kV/11 kV, 50 Hz, 20,000 kVA single phase transformer, the optimal frequency calculated is 18.231 Hz, and the corresponding source capacity and demagnetization time are 425 kVA and 509 s, respectively. Further, this method is applied to a small toroidal transformer, and the results reveal that demagnetization with a 12.5 Hz source will make an excellent tradeoff between source demands and demagnetization time.