What are high-frequency events?
Power quality disturbances generally are classified into broad categories of high frequency, voltage, distortion and fundamental frequency variations. High frequency events or disturbances refer to voltages with frequency components significantly higher than the nominal frequency line of 60 hertz. Important characteristics of a high-frequency event include maximum voltage level, energy content, rise time, phase angle and frequency of occurrence. High frequency events occur in several distinct varieties, each with characteristics that may help identify the source of the disturbance and the relative distance from the monitoring station. A unidirectional impulse is a high frequency, transient wave of current, voltage or power of unidirectional polarity. Impulses of a purely unidirectional nature generally are generated within a facility, or close by, without passing through a transformer. An oscillatoy impulse has both positive and negative polarity and poses two problems: first is the im
