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US4247879A
Expired / Lapsed
US
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People protecting ground fault circuit breaker utilizing waveform characteristics
Assignee: Westinghouse Electric Corp
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Filing: 1978-04-19
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Granted: 1981-01-27
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Expires: 1998-04-19
Abstract
Abstract A ground fault circuit breaker is provided which includes means for sensing ground fault current and for analyzing the waveform of the ground fault current. An operating mechanism automatically separates the contacts of the circuit breaker upon detection of ground fault current waveforms corresponding to the waveform of current passing through human skin. In a preferred embodiment, means are provided to synchronously detect the third harmonic component of ground fault current using phase and amplitude information to determine the presence of a ground fault path through human skin. Alternatively, means are provided to sense peak and average values of ground fault current and to trip the breaker whenever the ratio of peak to average ground fault current exceeds a predetermined level. In another alternative, the slope of the ground fault current at zero crossing is detected and compared to the ground fault current peaks. Whenever the ratio of peak current to zero crossing slope exceeds a predetermined level, the mechanism of the breaker is tripped.
Inventors
- 👤 Robert T. Elms
- 👤 Joseph C. Engel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:20
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H3/50; H02H3/52
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
111 words
People-protecting ground fault circuit breaker apparatus, comprising: separable contacts; means operable upon actuation to automatically separate said contacts to trip said apparatus; means for sensing ground fault current through said contacts; and, means for analyzing the shape of the waveform of said ground fault current comprising means responsive to peak ground fault current and average ground fault current, and means for comparing the ratio of peak-to-average ground fault current to a predetermined reference value corresponding to a peak-to-average ratio produced by human ground fault current of a specified tripping level, said analyzing means actuating said separating means whenever the detected ratio of peak-to-average ground fault current exceeds said predetermined reference value.
Claim 2
Dependent Claim
111 words
People-protecting ground fault circuit breaker apparatus, comprising: separable contacts; means operable upon actuation to automatically separate said contacts to trip said apparatus; means for sensing ground fault current through said contacts; and, means for analyzing the shape of the waveform of said ground fault current comprising means responsive to peak ground fault current and average ground fault current, and means for comparing the ratio of peak-to-average ground fault current to a predetermined reference value corresponding to a peak-to-average ratio produced by human ground fault current of a specified tripping level, said analyzing means actuating said separating means whenever the detected ratio of peak-to-average ground fault current exceeds said predetermined reference value.
Claim 3
Dependent Claim
138 words
People-protecting ground fault circuit breaker apparatus, comprising: separable contacts; means operable upon actuation to automatically separate said contacts to trip said apparatus; means for sensing ground fault current through said contacts; and, means for analyzing the shape of the waveform of said ground fault current, said analyzing means comprising means responsive to peak ground fault current and means responsive to the slope of the waveform of said ground fault current at zero crossing, said waveform analyzing means also comprising means for computing the ratio of said peak ground fault current to said slope and for comparing said ratio to a reference value corresponding to a peak-to-slope ratio produced by human ground fault current of a specified tripping level, said analyzing means operating said contact separating means upon detection of a value of said ratio greater than said reference.
Claim 4
Dependent Claim
138 words
People-protecting ground fault circuit breaker apparatus, comprising: separable contacts; means operable upon actuation to automatically separate said contacts to trip said apparatus; means for sensing ground fault current through said contacts; and, means for analyzing the shape of the waveform of said ground fault current, said analyzing means comprising means responsive to peak ground fault current and means responsive to the slope of the waveform of said ground fault current at zero crossing, said waveform analyzing means also comprising means for computing the ratio of said peak ground fault current to said slope and for comparing said ratio to a reference value corresponding to a peak-to-slope ratio produced by human ground fault current of a specified tripping level, said analyzing means operating said contact separating means upon detection of a value of said ratio greater than said reference.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-01-27 | 1984-07-28 | 1985-01-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-27 | 1988-07-28 | 1989-01-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-27 | 1992-07-28 | 1993-01-27 | $7700.00 | Window Closed / Lapsed |