US3696366A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ground detector system having fast response and decoupling of detector circuit
Assignee: Edwards Co Inc
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Filing: 1971-03-22
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Granted: 1972-10-03
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Expires: 1991-03-22
Abstract
Abstract A detector is disclosed which senses ground currents exceeding a predetermined magnitude in either one of a pair of line wires. A counter causes each line to be periodically and alternately connected to the detector for individual sensing of each line. An alarm system is provided which is responsive to a signal from the detector to generate a warning signal when a current exceeding said predetermined magnitude is sensed. The structure includes means for connecting each line to the detector and for responding to the alarm signal by decoupling the detector from the lines to thereby eliminate any contribution to the ground current which might be contributed by the presence of the detector coupled to the lines.
Inventors
- 👤 Charles H Parsons
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:13
CPC Classifications
G; G01; G01R; G01R19/00; G01R19/165; G01R19/16566; G01R19/16571; H; H02; H02H; H02H3/00; H02H3/02; H02H3/04
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
117 words
A detector for sensing ground currents which exceed a predetermined magnitude in either one of a pair of power lines wherein a counter couples each line alternately to the detector for individual sensing of each line, and alarm means coupled to the detector for generating a warning signal in response to the detection of a ground current exceeding said predetermined magnitude wherein the improvement comprises: control means for selectively connecting each line to the detector, and responsive to the alarm means for decoupling the detector from the lines upon the detection of a current exceeding said predetermined magnitude to eliminate any contribution to the sensed ground currents occasioned by the coupling of the detector to said lines.
Claim 2
Dependent Claim
117 words
A detector for sensing ground currents which exceed a predetermined magnitude in either one of a pair of power lines wherein a counter couples each line alternately to the detector for individual sensing of each line, and alarm means coupled to the detector for generating a warning signal in response to the detection of a ground current exceeding said predetermined magnitude wherein the improvement comprises: control means for selectively connecting each line to the detector, and responsive to the alarm means for decoupling the detector from the lines upon the detection of a current exceeding said predetermined magnitude to eliminate any contribution to the sensed ground currents occasioned by the coupling of the detector to said lines.
Claim 3
Dependent Claim
30 words
The detector as described in claim 1 wherein the detector exhibits a characteristic impedance having a magnitude substantially less than anticipated ground fault impedances for fast accurate ground fault detection.
Claim 4
Dependent Claim
40 words
The detector as described in claim 1 and further comprising: recoupling means responsive to the counter for recoupling the detector to the lines such that the detector may periodically test for continuation of a ground current exceeding said predetermined magnitude.
Claim 5
Dependent Claim
44 words
The detector as described in claim 3 wherein said recoupling means is periodically activated each time the counter reaches a predetermined count, and wherein said detector is responsive thereto for re-establishing said warning signal upon detection of a ground current exceeding said predetermined magnitude.
Claim 6
Dependent Claim
30 words
The detector as described in claim 4 wherein said recoupling means comprises: NAND gate means operative for producing an output signal in response to said predetermined count of said counter.
Claim 7
Dependent Claim
30 words
The detector as described in claim 1 and further comprising: switching means responsive to a potential indicative of a ground current exceeding said predetermined magnitude for activating said alarm means.
Claim 8
Dependent Claim
34 words
The detector as described in claim 6 wherein said switching means comprises: a transistor which is rendered conducting when the magnitude of said potential is indicative of a ground current exceeding said predetermined magnitude.
Claim 9
Dependent Claim
41 words
The detector as described in claim 7 wherein said alarm means includes: bistable means, responsively coupled to the switching means, and having first and second conductance states, for producing first and second output signals indicative of normal and alarm conditions, respectively.
Claim 10
Dependent Claim
17 words
The detector as described in claim 8 wherein said bistable means comprises: a solid state bistable multivibrator.
Claim 11
Dependent Claim
53 words
The detector as described in claim 8 wherein said alarm means further includes: a device coupled to the bistable means and normally controlled by said first conductance state for providing an indication of the normal condition; and activated for providing a warning signal when said bistable means is in said second conductance state.
Claim 12
Dependent Claim
45 words
The detector as described in claim 1 wherein said counter comprises: a four bit counter coupled to the pair of power lines for producing odd and even output pulses in response to signals indicative of alternate cycles of power applied to said pair of lines.
Claim 13
Dependent Claim
74 words
The detector as described in claim 11 wherein said control means includes: at least first and second AND gate means coupled to the counter and having inputs derived from the even and odd outputs of said counter respectively, each of said first and second gates alternately activated by said counter outputs and deactivated in response to the sensing of ground currents exceeding said predetermined magnitude for decoupling said detector from said pair of lines.
Claim 14
Dependent Claim
94 words
The detector as described in claim 1 wherein said detector further comprises: a bridge rectifier and transistor switching means coupled thereto for each line, each of said transistors being activated in response to alternate counts of said counter for conducting current signals from said bridge recTifier, and a voltage divider means coupled to the outputs of the transistor switching means for producing a potential indicative of the magnitude of said current signals, and wherein said alarm means is activated when the potential exceeds a level indicative of a ground current exceeding said predetermined magnitude.
Claim 15
Dependent Claim
53 words
The detector as described in claim 1 wherein said counter comprises: a one stage counter having an output for each line responsive to the line frequency for producing an output signal; and a multi-stage counter having a number of output leads and which produces a reset signal on one of its output leads.
Claim 16
Dependent Claim
47 words
The detector as described in claim 14 and further including: AND gate means coupled to each output of the one stage counter and gated with counter; output of the alarm means such that each AND gate means alternately and selectively energizes the detector for its associated line.
Claim 17
Dependent Claim
78 words
The detector as described in claim 15 and further including: alarm reset means for the alarm means activated by the last stage of said multi-stage counter, and counter reset means activated in response to the alarm signal for resetting the multi-stage counter to zero counts; whereby the single stage counter is synchronized with the multi-stage counter for checking the line on which an alarm occurred first so that the detector has minimal influence on the ground fault current.
Claim 18
Dependent Claim
36 words
The detector as described in claim 1 and which further includes: auxiliary decoupling means for each line responsive to a level of ground current higher than said predetermined magnitude for decoupling said detector from said line.
Claim 19
Dependent Claim
35 words
The detector as described in claim 17 wherein said auxiliary decoupling means comprises: a transistor for limiting the sensed ground current signal to less than a predetermined overload current just higher than said predetermined magnitude.
Claim 20
Dependent Claim
32 words
The detector as described in claim 17 wherein said detector further include: a phototransistor means for selectively coupling the detector to the line, when activated by alternate opposite outputs of the counter.
Claim 21
Dependent Claim
41 words
The detector as described in claim 17 and which further includes: a transformer having two secondaries wound out of phase one with the other for coupling, when activated by alternate opposite outputs of the counter, each associated line to the detector.
References Cited (Backward Citations)
US1055018A
Cited
US2700125A
Cited
US3066284A
Cited
US3076601A
Cited
US3267458A
Cited
US3467858A
Cited
US3559055A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-03 | 1976-04-03 | 1976-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-03 | 1980-04-03 | 1980-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-03 | 1984-04-03 | 1984-10-03 | $7700.00 | Window Closed / Lapsed |