A system for capturing and presenting short-duration voltage impulses on AC power lines

Voltage impulses with frequency components substantially above the fundamental frequency can be found on AC power distribution systems. A system for capturing these impulses and presenting them for analysis is described. The system records both the impulse waveform and the fundamental waveform shape in digital FIFO (first in, first out) buffers. Both signals are continuously recorded; recording continues for an interval of time after triggering that is shorter than the depth of the FIFO buffers, yielding detailed pretrigger and posttrigger information. The results of some preliminary field investigations are discussed. They indicate that some terminology that has previously been used to describe impulse parameters, such as duration,' may no longer be useful. Initial analysis of impulse waveforms indicates that some impulse sources can be identified by their waveforms. >