Importance

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Abstract

Voltage and current signals in a power distribution system are converted to digital data by scaling and sampling the signals and simultaneously comparing all the samples to a digitally generated ramp converted to analog form. When a sample intersects the ramp, the digital number representing the ramp amplitude is loaded into storage without interrupting the ramp generation sequence. A zero cross detector detects a zero crossing for a voltage or current. Sampling is initiated by a programmable, interval timer which is loaded with a selected time interval from a microcomputer and initiates the sampling a selected time interval after the zero cross is detected. The samples are taken during representative, repetitive cycles at angularly spaced positions in a composite cycle to form a group of samples for the composite cycle for each of the signals of the power distribution system. The samples are uniformly spaced in the composite cycle but periodically the sample positions are sequenced through a set of different sample positions.

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First Claim