The present disclosure is directed towards a method for protecting a multi-phase autotransformer for an aircraft including the steps of receiving values of current input into and output from the first and second phases; determining, as a function of these received values, values of current representative of the operation of the phases; determining, as a function of these determined values, a value representative of a homopolar current flowing in the first phase; comparing, in a first comparison, the value representative of the homopolar current flowing in the first phase with a first predetermined threshold value; and controlling the values of current input into the phases as a function of the first comparison.