Patent ID: 7960977

Claim:
A method for determining the change in insulating ability of the insulation provided between two objects of an inductively operating element, where at least one of the objects is a winding, and comprising the steps of: obtaining a first frequency spectrum associated with a frequency response to a signal of varying frequency, where said signal of varying frequency is a signal that can be applied to a first object of the inductively operating element and the frequency response is obtainable from a second object of the inductively operating element, comparing the obtained first frequency spectrum with a second reference frequency spectrum, detecting a peak in the obtained first frequency spectrum that does not appear in the second reference frequency spectrum, analyzing the shape of the detected peak, and determining the change in insulating ability based on the analyzed shape of the detected peak wherein the step of determining the change in insulating ability includes determining an amount of degraded insulating ability based on the frequency (f 1 ) of the peak value of the peak.