The present disclosure relates to a method for determining an undesired condition in an electrical drive system comprising an electrical machine and an electrical drive, wherein the method comprises a) obtaining a measured signal of an electrical or mechanical parameter concerning the electrical drive system, b) obtaining a frequency spectrum of the measured signal, which frequency spectrum contains a measured frequency component, c) determining whether the measured frequency component is within a predetermined distance from a trend line, which trend line is associated with only one specific frequency component of the electrical or mechanical parameter present during a specific undesired condition,, d) on the condition that the measured frequency component is within the predetermined distance from the trend line increasing a counter associated with the trend line, g) repeating steps a) to d), wherein in case the counter reaches a predetermined number within a predetermined number of iterations of steps a) to d), and f) determining based on that the counter reaches the predetermined number that the electrical drive system is subjected to the undesired condition associated with the trend line.