Method of changing the active winding number of a regulating winding in an electrical installation, wherein - the regulating winding is coupled to an alternating current mains with a predetermined period duration T, is designed for a predetermined nominal current strength IN and comprises a first and a second tap (121, 122); - switching over takes place in accordance with a predetermined switching sequence plan from a first continuous current state, in which a load current (iL) flows from the first tap to a load output line by way of a first main path and the second tap is separated from the load output line, to a second continuous current state, in which the load current flows from the second tap to the load output line by way of a second main path and the first tap is separated from the load output line; - the switching sequence plan prescribes that - starting from the first continuous current state in a switching step a the first tap is or remains connected with the load output line by way of a first transition path and the first main path is isolated; - in a switching step b after switching step a the second tap is connected with the load output line by way of a second transition path so that a circular current iK flows through the transition paths due to the step voltage between the taps (121, 122); - in a switching step c after switching step b the first tap is separated from the load output line; and - in a switching step d after switching step c the second tap is connected with the load output line by way of the second main path; - at at least one predetermined test instant tT between switching step a and switching step c it is tested whether the first main path is isolated; - a current strength IL of the load current is determined; and - the test instant tT depends on the load current strength IL. - the regulating winding is coupled to an alternating current mains with a predetermined period duration T, is designed for a predetermined nominal current strength IN and comprises a first and a second tap (121, 122); - switching over takes place in accordance with a predetermined switching sequence plan from a first continuous current state, in which a load current (iL) flows from the first tap to a load output line by way of a first main path and the second tap is separated from the load output line, to a second continuous current state, in which the load current flows from the second tap to the load output line by way of a second main path and the first tap is separated from the load output line; - the switching sequence plan prescribes that - starting from the first continuous current state in a switching step a the first tap is or remains connected with the load output line by way of a first transition path and the first main path is isolated; - in a switching step b after switching step a the second tap is connected with the load output line by way of a second transition path so that a circular current iK flows through the transition paths due to the step voltage between the taps (121, 122); - in a switching step c after switching step b the first tap is separated from the load output line; and - in a switching step d after switching step c the second tap is connected with the load output line by way of the second main path; - starting from the first continuous current state in a switching step a the first tap is or remains connected with the load output line by way of a first transition path and the first main path is isolated; - in a switching step b after switching step a the second tap is connected with the load output line by way of a second transition path so that a circular current iK flows through the transition paths due to the step voltage between the taps (121, 122); - in a switching step c after switching step b the first tap is separated from the load output line; and - in a switching step d after switching step c the second tap is connected with the load output line by way of the second main path; - at at least one predetermined test instant tT between switching step a and switching step c it is tested whether the first main path is isolated; - a current strength IL of the load current is determined; and - the test instant tT depends on the load current strength IL.