A floating-window algorithm for detecting certain power line faults that disrupt sensitive electronic loads

A floating-window algorithm is described that performs a triggering function that detects changes in the voltage waveform which can disrupt sensitive electronic loads. The proposed algorithm is an extension of a digital equivalent of G.W.Allen's (see IEEE Trans. Power Appl. Syst., vol. PAS-90, p.2604-9, May 1971) concept of an ideal-template-matching triggering mechanism, in which the digitized samples of a voltage waveform would be compared with the digitized values of an ideal waveform (in this case, the ideal sine wave). The proposed floating-window trigger mechanism uses each cycle of the AC waveform as a template for the succeeding cycle. Consequently, it triggers on a change in the shape of the voltage wave form. The proposed triggering function can be used to capture digitally sampled power line disturbances so their cause can be identified and corrected. >