Direct current machine monitoring system and method

A direct current machine monitoring system includes a sensor configured to monitor a load current of the machine and provide a signal indicative of an alternating current component of the load current; and a computer configured for: transforming the signal to provide a time domain transformation of the alternating current component of the load current, identifying features in the time domain transformation corresponding to sparking, and assessing a condition of the direct current machine using the features. The transform may be performed using a wavelet transform. The features may be used to determine a sparking intensity and a sparking frequency in the direct current machine, which may be used to determine a sparking index for assessing the condition of the direct current machine. The sparking index may be compared to a limit value, and statistical analysis may be performed on the sparking index.