Method for determining asymmetric vibrations in an electric device

A method for identifying a DC current component in an electrical device that is connected to a high-voltage supply grid, the method comprising:

• providing a portable unit with at least one acoustic sensor;
• acquiring acoustic signals at different locations in a vicinity of the electrical device with the at least one acoustic sensor, wherein a software interactively guides a user during the acquiring step and wherein the acoustic signals capture operating noise of the electrical device;
• breaking down the acoustic signals into frequency components by way of a Fourier transformation to obtain a frequency spectrum;
• ascertaining even and odd frequency components of the frequency spectrum based on a fundamental frequency of the high-voltage supply grid and determining a ratio R between the odd and even frequency components;
• and
• when the ratio R exceeds a predetermined threshold value, concluding that a DC current component is present in the electrical device.