US3611035A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ground fault protective system having grounded neutral protection
Assignee: PROVIDENT INDUSTRIES Inc
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Filing: 1970-06-08
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Granted: 1971-10-05
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Expires: 1990-06-08
Abstract
Abstract Ground fault protective system and method in which a high frequency tickler voltage is induced on the neutral conductor of a distribution system to indicate inadvertent grounding of that conductor and/or to interrupt the flow of current in the distribution system in response to grounding of the neutral conductor.
Inventors
- 👤 Ellwood S Douglas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:46
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/33; H02H3/331; H02H3/16; H02H3/17
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
133 words
In a protective device adapted for connection in a power distribution system having a neutral conductor and at least one line conductor carrying current between a source and a load, said neutral conductor being grounded at said source, ground fault sensing means connected for monitoring the flow of current in the line and neutral conductors and producing a fault signal when the total current in the line conductors is not equal to the current in the neutral conductor, and tickler means coupled to said neutral conductor for producing a high frequency current therein upon grounding of said neutral conductor in addition to the grounding at said source, said high-frequency current serving to produce a current imbalance in the line and neutral conductors, causing said ground fault sensing means to produce a fault signal.
Claim 2
Dependent Claim
133 words
In a protective device adapted for connection in a power distribution system having a neutral conductor and at least one line conductor carrying current between a source and a load, said neutral conductor being grounded at said source, ground fault sensing means connected for monitoring the flow of current in the line and neutral conductors and producing a fault signal when the total current in the line conductors is not equal to the current in the neutral conductor, and tickler means coupled to said neutral conductor for producing a high frequency current therein upon grounding of said neutral conductor in addition to the grounding at said source, said high-frequency current serving to produce a current imbalance in the line and neutral conductors, causing said ground fault sensing means to produce a fault signal.
Claim 3
Dependent Claim
29 words
A protective device as in claim 1 together with means connected for interrupting the flow of current in said line and neutral conductors in response to said fault signal.
Claim 4
Dependent Claim
23 words
A protective device as in claim 1 wherein said tickler means includes pulse generator means coupled to said neutral conductor through a transformer.
Claim 5
Dependent Claim
17 words
A protective device as in claim 3 wherein said pulse generator means includes a semiconductor switching element.
Claim 6
Dependent Claim
55 words
A protective device as in claim 3 wherein said transformer includes a toroidal core of magnetic material, a primary winding having at least one turn wound on said core and connected to the output of said pulse generator means, and a secondary winding of at least one turn connected in series with said neutral conductor.
Claim 7
Dependent Claim
35 words
A protective device as in claim 1 wherein said tickler means is also coupled for producing a high-frequency current in one of the line conductors upon shorting of the line conductor to an unprotected conductor.
Claim 8
Dependent Claim
34 words
A protective device as in claim 6 wherein said tickler means includes a transformer having a plurality of secondary windings of at least one turn connected in series with the line and neutral conductors.
Claim 9
Dependent Claim
130 words
In a ground fault protective device of the type having ground fault sensing means for monitoring the flow of current in line and neutral conductors interconnecting a source and a load, the neutral conductor being connected to ground at the source, a pulse generator adapted for producing voltage pulses at a rate greater than the frequency of the current from said source, and a transformer having a primary winding connected for receiving the output of said pulse generator and a secondary winding of at least one turn connected in series with said neutral conductor for inducting said voltage pulses on said neutral conductor, said voltage pulses producing a current in said neutral conductor upon grounding of the same, thereby causing imbalance in the currents in said line and neutral conductors.
Claim 10
Dependent Claim
130 words
In a ground fault protective device of the type having ground fault sensing means for monitoring the flow of current in line and neutral conductors interconnecting a source and a load, the neutral conductor being connected to ground at the source, a pulse generator adapted for producing voltage pulses at a rate greater than the frequency of the current from said source, and a transformer having a primary winding connected for receiving the output of said pulse generator and a secondary winding of at least one turn connected in series with said neutral conductor for inducting said voltage pulses on said neutral conductor, said voltage pulses producing a current in said neutral conductor upon grounding of the same, thereby causing imbalance in the currents in said line and neutral conductors.
Claim 11
Dependent Claim
28 words
A ground fault protective device as in claim 8 wherein said pulse generator includes a diac and a timing capacitor connected for controlling the firing of said diac.
Claim 12
Dependent Claim
101 words
In a method for preventing a differential ground fault protective device from being rendered inoperable by grounding at the load of the neutral conductor of a power distribution system in which the neutral conductor is normally grounded at its source end, the steps of generating a tickler voltage at a frequency higher than that of the current in the distribution system and inducing the tickler voltage on the neutral conductor so that upon grounding of said conductor a current flows therein, producing an imbalance in the currents in the distribution system conductors and causing actuation of the ground fault protective device.
Claim 13
Dependent Claim
101 words
In a method for preventing a differential ground fault protective device from being rendered inoperable by grounding at the load of the neutral conductor of a power distribution system in which the neutral conductor is normally grounded at its source end, the steps of generating a tickler voltage at a frequency higher than that of the current in the distribution system and inducing the tickler voltage on the neutral conductor so that upon grounding of said conductor a current flows therein, producing an imbalance in the currents in the distribution system conductors and causing actuation of the ground fault protective device.
Claim 14
Dependent Claim
46 words
A method as in claim 10 together with the additional step of inducing the tickler voltage on the other conductors in the distribution system to prevent the protective device from being rendered inoperable by the shorting of one of these other conductors to an unprotected conductor.
References Cited (Backward Citations)
US3525018A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-10-04 | 1975-04-05 | 1975-10-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-10-04 | 1979-04-05 | 1979-10-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-10-04 | 1983-04-05 | 1983-10-05 | $7700.00 | Window Closed / Lapsed |