A method for monitoring operation of a switching device in a power system , wherein a load is connected to a power source through the switching device , the method comprising: obtaining by a device a measurement of voltage at a source side from a first measurement equipment connected to the device , and a measurement of voltage at a load side from a second measurement equipment connected to the device , wherein the load comprises a plurality of windings, and a coupling between at least two phases of a winding of the plurality of windings or at least two windings of the plurality of windings; characterised by determining one of a gap voltage associated with electrical switching of at least one pole of a plurality of poles of the switching device based the measurement of the voltage at the source side and the measurement of the voltage at the load side, and a line to line voltage of at least one pole of a plurality of poles of the switching device based on a line measurement associated with at least one winding of the plurality of windings of the load ; monitoring whether the gap voltage for the at least one pole meets a threshold and the line to line voltage for the at least one pole meets a threshold; determining an electrical switching instant for the at least one pole when the gap voltage for the at least one pole meets the threshold or the line to line voltage for the at least one pole meets the threshold; and determining a mechanical operating time deviation for the at least one pole based on the electrical switching instant, wherein the mechanical operating time deviation is used for evaluating release instant of an output command to the switching device for operating the at least one pole of the switching device at the electrical switching instant. obtaining by a device a measurement of voltage at a source side from a first measurement equipment connected to the device , and a measurement of voltage at a load side from a second measurement equipment connected to the device , wherein the load comprises a plurality of windings, and a coupling between at least two phases of a winding of the plurality of windings or at least two windings of the plurality of windings; characterised by determining one of a gap voltage associated with electrical switching of at least one pole of a plurality of poles of the switching device based the measurement of the voltage at the source side and the measurement of the voltage at the load side, and a line to line voltage of at least one pole of a plurality of poles of the switching device based on a line measurement associated with at least one winding of the plurality of windings of the load ; monitoring whether the gap voltage for the at least one pole meets a threshold and the line to line voltage for the at least one pole meets a threshold; determining an electrical switching instant for the at least one pole when the gap voltage for the at least one pole meets the threshold or the line to line voltage for the at least one pole meets the threshold; and determining a mechanical operating time deviation for the at least one pole based on the electrical switching instant, wherein the mechanical operating time deviation is used for evaluating release instant of an output command to the switching device for operating the at least one pole of the switching device at the electrical switching instant. <EOS>