Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1994-11-18
1997-05-06
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361 79, 324120, 324 7658, 324500, 341123, H02H 318
Patent
active
056277180
ABSTRACT:
A circuit interrupter samples waveforms in a protected circuit by taking samples in pairs spaced 90 electrical degrees apart. The sum of the squares of samples in each pair, which is representative of the RMS value of the fundamental frequency of the waveform, is used for instantaneous protection by comparing a running sum of the squares for the two most recent pairs of samples to a threshold representative of the instantaneous trip pick-up value. This sum of the squares of successive two pairs of samples is also used for short delay protection. A delay between successive pairs of samples is varied to produce a selected equivalent sampling rate after a given number of samples. Samples accumulated at this equivalent sampling rate, which is sixty-four samples per cycle in the preferred embodiment, are used for long delay protection and metering.
REFERENCES:
patent: 4672555 (1987-06-01), Hart et al.
patent: 5060166 (1991-10-01), Engel et al.
patent: 5233538 (1993-08-01), Wallis
Engel Joseph C.
Johnson Richard A.
Saletta Gary F.
Eaton Corporation
Gaffin Jeffrey A.
Moran Martin J.
Sherry Michael J.
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