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Patent US3676739A successfully refreshed from Google Patents.
US3676739A
Expired / Lapsed
US
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Mine power system ground continuity check circuit
Assignee: General Electric Co
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Filing: 1971-09-07
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Granted: 1972-07-11
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Expires: 1991-09-07
Abstract
Abstract A ground cable continuity check circuit for a power supply cable system having a grounding and a pilot conductor electrically interconnected remotely from the power supply. A source of electrical energy for the check circuit is provided through a constant current transformer having its secondary connected between the grounding and pilot conductors. A circuit including the coil of an undervoltage relay and the contacts of a current relay is connected across the constant current transformer primary. The current relay coil is connected in series with the constant current transformer secondary and the grounding and pilot conductors. A voltage breakdown device is connected across the constant current transformer secondary to divert current from the current relay coil when a high impedance appears in the ground circuit for opening the current relay contacts to disable the under voltage relay. The power supply system may have a main cable and at least one branch cable in which case the grounding and pilot conductor loops of the main cable and branch cable are interconnected by a current transformer having one coil connected in the main grounding and pilot conductor loop and the other coil connected between the grounding and pilot conductors of the branch circuit.
Inventors
- 👤 Donald E Neuhouser
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 05:00
CPC Classifications
H; H02; H02H; H02H11/00; H02H11/001
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
135 words
In a ground cable continuity check circuit for a power supply cable having a grounding conductor and a pilot conductor, said grounding conductor and said pilot conductor being electrically interconnected remotely of the power supply: a. a constant current source interconnecting said grounding and pilot conductors; b. current responsive means connected in series with said grounding and pilot conductors, said current responsive means having a first condition in response to a current of at least a predetermined level and a second condition when the current is less than the predetermined level; and c. voltage responsive means connected across said constant current source for selectively diverting current from said current responsive means to reduce the current therethrough below the predetermined level in response to the existence of a predetermined impedance between said grounding and pilot conductors.
Claim 2
Dependent Claim
135 words
In a ground cable continuity check circuit for a power supply cable having a grounding conductor and a pilot conductor, said grounding conductor and said pilot conductor being electrically interconnected remotely of the power supply: a. a constant current source interconnecting said grounding and pilot conductors; b. current responsive means connected in series with said grounding and pilot conductors, said current responsive means having a first condition in response to a current of at least a predetermined level and a second condition when the current is less than the predetermined level; and c. voltage responsive means connected across said constant current source for selectively diverting current from said current responsive means to reduce the current therethrough below the predetermined level in response to the existence of a predetermined impedance between said grounding and pilot conductors.
Claim 3
Dependent Claim
32 words
A ground cable continuity check circuit as set forth in claim 1 wherein: said constant current source includes a constant current transformer having its secondary connected between said grounding and pilot conductors.
Claim 4
Dependent Claim
52 words
A ground cable continuity check circuit as set forth in claim 2 wherein: said current responsive means includes a current relay having its coil connected in series with said constant current transformer secondary and said voltage responsive means includes a voltage breakdown device connected in parallel with said constant current transformer secondary.
Claim 5
Dependent Claim
193 words
In a ground cable continuity check circuit for a power supply cable having a grounding conductor and a pilot conductor, said grounding conductor and said pilot conductor Being electrically interconnected remotely of the power supply: a. a source of electric energy; b. a first circuit connected across said source of electric energy, including the coil of an under voltage relay and the contacts of a current relay; c. a second circuit connected across said source of electric energy, including the primary of a constant current transformer, the secondary of said constant current transformer being connected between said grounding and pilot conductors; d. the coil of said current relay being connected in series with said constant current transformer secondary, said current relay being effective only upon the flow of current of at least a predetermined level through its coil to close its contacts for enabling said under voltage relay; and e. voltage responsive means connected across said constant current transformer secondary for selectively diverting current from said current relay coil to reduce the current therethrough below the predetermined level in response to the existence of a predetermined impedance between said grounding and pilot conductors.
Claim 6
Dependent Claim
193 words
In a ground cable continuity check circuit for a power supply cable having a grounding conductor and a pilot conductor, said grounding conductor and said pilot conductor Being electrically interconnected remotely of the power supply: a. a source of electric energy; b. a first circuit connected across said source of electric energy, including the coil of an under voltage relay and the contacts of a current relay; c. a second circuit connected across said source of electric energy, including the primary of a constant current transformer, the secondary of said constant current transformer being connected between said grounding and pilot conductors; d. the coil of said current relay being connected in series with said constant current transformer secondary, said current relay being effective only upon the flow of current of at least a predetermined level through its coil to close its contacts for enabling said under voltage relay; and e. voltage responsive means connected across said constant current transformer secondary for selectively diverting current from said current relay coil to reduce the current therethrough below the predetermined level in response to the existence of a predetermined impedance between said grounding and pilot conductors.
Claim 7
Dependent Claim
211 words
In a ground cable continuity check circuit for a power supply cable system having grounding and pilot conductors; the power supply cable system having a main cable and at least one branch cable: a. said main cable including a main grounding conductor and a main pilot conductor electrically interconnected to form a closed loop normally of low impedance, a fault in said main grounding conductor causing a high impedance to appear across said main cable grounding and pilot conductor loop; b. said at least one branch cable including a branch grounding conductor and a branch pilot conductor interconnected to form a closed loop normally of low impedance, a fault in said branch grounding conductor causing a high impedance to appear across said branch cable grounding and pilot conductor loop; c. a current transformer having its primary connected in said main cable grounding and pilot conductor loop and its secondary connected between said branch grounding and pilot conductors so that a high impedance across said branch cable grounding and pilot conductor loop will cause a high impedance to appear across said main grounding and pilot conductor loop; and d. control means responsive to a predetermined high impedance across said main grounding and pilot conductor loop to deactivate the power supply cable system.
Claim 8
Dependent Claim
211 words
In a ground cable continuity check circuit for a power supply cable system having grounding and pilot conductors; the power supply cable system having a main cable and at least one branch cable: a. said main cable including a main grounding conductor and a main pilot conductor electrically interconnected to form a closed loop normally of low impedance, a fault in said main grounding conductor causing a high impedance to appear across said main cable grounding and pilot conductor loop; b. said at least one branch cable including a branch grounding conductor and a branch pilot conductor interconnected to form a closed loop normally of low impedance, a fault in said branch grounding conductor causing a high impedance to appear across said branch cable grounding and pilot conductor loop; c. a current transformer having its primary connected in said main cable grounding and pilot conductor loop and its secondary connected between said branch grounding and pilot conductors so that a high impedance across said branch cable grounding and pilot conductor loop will cause a high impedance to appear across said main grounding and pilot conductor loop; and d. control means responsive to a predetermined high impedance across said main grounding and pilot conductor loop to deactivate the power supply cable system.
Claim 9
Dependent Claim
120 words
A ground cable continuity check circuit as set forth in claim 5, wherein said control means includes; a. a constant current source interconnecting said main grounding and pilot conductors; b. current responsive means connected in said main grounding pilot conductor loop, said current responsive means having a first condition in response to a current of at least a predetermined level and a second condition when the current is less than the predetermined level, and c. voltage responsive means connected across said constant current source for selectively directing current from said current responsive means to reduce the current therethrough below the predetermined level in response to the existence of a predetermined high impedance across said main grounding and pilot conductor loop.
Claim 10
Dependent Claim
33 words
A ground cable continuity check circuit as set forth in claim 5 wherein: said constant current source includes a constant current transformer having its secondary connected between said main grounding and pilot conductors.
Claim 11
Dependent Claim
52 words
A ground cable continuity check circuit as set forth in claim 7 wherein: said current responsive means includes a current relay having its coil connected in series with said constant current transformer secondary and said voltage responsive means includes a voltage breakdown device connected in parallel with said constant current transformer secondary.
Claim 12
Dependent Claim
179 words
A ground cable continuity check circuit as set forth in claim 5 wherein said control means includes: a. a source of electric energy; b. a first circuit connected across sAid source of electric energy, including the coil of an under voltage relay and the contacts of a current relay; c. a second circuit connected across said source of electric energy, including the primary of a constant current transformer, the secondary of said constant current transformer being connected between said main grounding and pilot conductors; d. the coil of said current relay being connected in series with said constant current transformer secondary, said current relay being effective only upon the flow of current of at least a predetermined level through its coil to close its contacts for enabling said under voltage relay; and e. voltage responsive means connected across said constant current transformer secondary for selectively diverting current from said current relay coil to reduce the current therethrough below the predetermined level in response to the existence of a predetermined high impedance across said main grounding and pilot conductor loop.
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) | 1975-07-11 | 1976-01-10 | 1976-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-11 | 1980-01-10 | 1980-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-11 | 1984-01-10 | 1984-07-11 | $7700.00 | Window Closed / Lapsed |