A method, device and computer program product 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. The device includes an analyzing unit, which obtains a first frequency spectrum associated with a frequency response to a signal of varying frequency, where the signal of varying frequency 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, compares the obtained first frequency spectrum with a second reference frequency spectrum, detects a peak in the obtained first frequency spectrum that does not appear in the second reference frequency spectrum, analyzes the shape of the detected peak, and determines the change in insulating ability based on the analyzed shape.