US3737765A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Isolated power ground fault detector system
Assignee: Hubbell Inc
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Filing: 1971-06-21
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Granted: 1973-06-05
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Expires: 1991-06-21
Abstract
Abstract A ground fault detector system for isolated power lines, especially those for use with operating room and intensive care monitoring equipment including an isolated test circuit arrangement for checking the operation of the system, that does not itself introduce potentially hazardous and dangerous ground faults into the isolated power lines being monitored. More specifically, the isolated power ground fault detector system of the present invention functions to alternately connect a detector circuit to the power lines at a frequency which is a submultiple of the source frequency. The detector senses both capacitive and resistive ground faults and provides an output voltage signal representative of the magnitude of the ground fault. This output voltage signal is compared to a reference voltage in a voltage comparator which activates alarms and indicators if the ground fault exceeds a preset threshold value. The system also includes a test circuit for checking the operation of the system which when actuated simultaneously switches the detector system from the isolated power lines to auxiliary power lines and introduces a simulated capacitive resistive fault into either of the auxiliary lines. By this arrangement, the system may be checked without introducing a potentially hazardous and dangerous ground fault into the isolated power line supplying the equipment.
Inventors
- 👤 S Lee
- 👤 E Burns
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 01:24
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/16; G01R27/18
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
164 words
A ground fault detecting system for detecting ground faults that may occur on any individual line conductor of power lines isolated from ground comprising: detector means for detecting ground faults that may occur on a line conductor; line switching means connected between said detector means and said power line for alternately connecting each of said line conductors of said power lines to said detector means; indicator means connected to said detector means for providing an indication when a ground fault is detected; and test circuit means connected between said line switching means and said power lines for testing the operation of the system, said test circuit means including auxiliary conductors independent of said power lines, a simulated ground fault adapted to be selectively connected to individual conductors of said auxiliary conductors and switching means for switching said line switching means from said power lines to said auxiliary conductors and simultaneously selectively connecting said simulated ground fault to an individual conductor of said auxiliary conductor.
Claim 2
Dependent Claim
164 words
A ground fault detecting system for detecting ground faults that may occur on any individual line conductor of power lines isolated from ground comprising: detector means for detecting ground faults that may occur on a line conductor; line switching means connected between said detector means and said power line for alternately connecting each of said line conductors of said power lines to said detector means; indicator means connected to said detector means for providing an indication when a ground fault is detected; and test circuit means connected between said line switching means and said power lines for testing the operation of the system, said test circuit means including auxiliary conductors independent of said power lines, a simulated ground fault adapted to be selectively connected to individual conductors of said auxiliary conductors and switching means for switching said line switching means from said power lines to said auxiliary conductors and simultaneously selectively connecting said simulated ground fault to an individual conductor of said auxiliary conductor.
Claim 3
Dependent Claim
60 words
The ground fault detecting system of claim 1 further comprising: comparator means connected between said detector means and said indicator means for comparing an output signal of said detector means to a predetermined threshold value; and wherein said indicator means provide an indication of a ground fault only when said output signal of said detector means exceeds said threshold value.
Claim 4
Dependent Claim
50 words
The ground fault detecting system of claim 2 wherein said output signal of said detector means is a voltage representative of the magnitude of a detected ground fault, said comparator means is a voltage comparator and said threshold value is a selectively adjustable reference voltage supplied to said voltage comparator.
Claim 5
Dependent Claim
62 words
The ground fault detecting system of claim 1 wherein said indicator means includes a remOte indicator isolated from said system, a selectively connected sound alarm, and a pair of pilot lights, one of said pilot lights being energized so long as no ground fault is detected and the other of said pilot lights being energized only when a ground fault is detected.
Claim 6
Dependent Claim
125 words
The ground fault detecting system of claim 1 wherein said line switching means includes: a plurality of solid state switching devices connected to said detector means, each of which are adapted to be connected through said test circuit means to an individual line conductor of said power lines or an individual conductor of said auxiliary conductors; and frequency divider means connected to a power source supplying power to said power lines for dividing the frequency of said power source, said frequency divider means being connected to each of said solid state switching devices to alternately turn said solid state switching devices on so as to alternately connect said line conductors of said power lines or said conductors of said auxiliary conductors to said detector means.
Claim 7
Dependent Claim
38 words
The ground fault detecting system of claim 5 wherein said line switching means further includes a plurality of resistors each of which are connected between said test circuit means and individual ones of said solid state switching devices.
Claim 8
Dependent Claim
107 words
The ground fault detecting system of claim 1 wherein said switching means of said test circuit means comprise a plurality of push buttons, one for each line conductor of said power lines, each of said push buttons including a contact bar for each of said line conductors of said power lines which in their normal rest position connect said line conductors to said line switching means and in their actuated position connect said conductors of said auxiliary conductors to said line switching means and a contact bar which in its actuated position connects a simulated ground fault between an individual conductor of said auxiliary conductor and ground.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-04 | 1976-12-04 | 1977-06-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-04 | 1980-12-04 | 1981-06-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-04 | 1984-12-04 | 1985-06-05 | $7700.00 | Window Closed / Lapsed |