Electrical transmission or interconnection systems – Plural supply circuits or sources – Substitute or emergency source
Patent
1989-09-08
1993-07-20
Pellinen, A. D.
Electrical transmission or interconnection systems
Plural supply circuits or sources
Substitute or emergency source
364487, 340661, H02H 324, H02H 350
Patent
active
052296512
ABSTRACT:
AC line monitoring is provided for uninterruptible power supplies to detect AC power system line faults by comparing the presently received cycle of the AC power line signal with a reference waveform. The reference waveform is formed of a composite of waveforms from prior cycles which adapts over time to the shape of the AC power line waveform, so that waveforms other than pure sinusoids can be accepted without triggering false fault conditions. The composite reference waveform may be formed of essentially all samples from prior cycles with exponentially decaying weighting. An excessive deviation of the current waveform from the reference waveform results in a fault being detected which causes switching of the uninterrupible power supply to provide backup power. The RMS value of the power line voltage is also estimated on a substantially real time basis, preferably by calculating the RMS value of the reference waveform, to provide a fault condition signal when the estimated RMS value falls below a selected level, which also can be utilized to cause switching of the uninterruptible power supply.
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Baxter, Jr. Richard V.
Stich Frederick A.
Best Power Technology, Inc.
Fleming Fritz M.
Pellinen A. D.
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