US3558981A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ground relay system for multiple substation protection
Assignee: ABB Inc USA
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Filing: 1969-06-13
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Granted: 1971-01-26
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Expires: 1989-06-13
Abstract
Abstract A ground relay system for multiple substation protection employing a plurality of current transformer sensors. In a threephase electrical system, one such current transformer is connected to sense the current flow from ground to the common neutral conductor for the multiple sources employed and serves to trip a circuit breaker connecting these multiple sources in a summing relationship when a ground fault is indicated. At the same time, the remaining current transformers serve to sense the current flow in the neutral conductor of the system and relay circuits activated thereby are conditioned by the operation of the first such current transformer to trip the circuit breaker or breakers associated with that portion of the system in which a ground fault is present. D R A W I N G
Inventors
- 👤 Stanley E Zocholl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 06:16
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/26; H02H7/261; H02H7/262
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
370 words
A system for detecting ground faults in a multistation multiphase power distribution network having a common neutral conductor comprising: first and second multiphase alternating current electric power buses; first switching means for connecting said first electric power bus to a first source of multiphase alternating current energy, said first switching means being equipped with a first normally deenergized trip coil and being openable to disconnect said first bus from said first source upon energization of said first trip coil; second switching means for connecting said second electric power bus to a second source of multiphase alternating current energy, said second switching means additionally being equipped with a second normally deenergized trip coil and being openable to disconnect said second bus from said second source upon energization of said second trip coil; third switching means for connecting said first electric power bus to said second electric power bus, said third switching means also being equipped with a third normally deenergized trip coil and being openable to disconnect said first bus from said second bus upon energization of said third trip coil; an electrical connection from said common neutral conductor to a point of alteRnating current ground potential; means including a first sensor inductively coupled to said electrical connection for generating a current to effect energization of said third trip coil upon the occurrence of a ground fault on one of said electric power buses; first normally disabled means including a second sensor inductively coupled to said common neutral conductor at a point intermediate said first alternating current energy source and said electrical connection for generating a current, when enabled, to effect energization of said first trip coil upon the occurrence of a ground fault on said first electric power bus; second normally disabled means including a third sensor inductively coupled to said common neutral conductor at a point intermediate said second alternating current energy source and said electrical connection for generating a current, when enabled, to effect energization of said second trip coil upon the occurrence of a ground fault on said second electric power bus; and with the generation of current to effect energization of said third trip coil also serving to enable said first and second normally disabled means.
Claim 2
Independent Claim
370 words
A system for detecting ground faults in a multistation multiphase power distribution network having a common neutral conductor comprising: first and second multiphase alternating current electric power buses; first switching means for connecting said first electric power bus to a first source of multiphase alternating current energy, said first switching means being equipped with a first normally deenergized trip coil and being openable to disconnect said first bus from said first source upon energization of said first trip coil; second switching means for connecting said second electric power bus to a second source of multiphase alternating current energy, said second switching means additionally being equipped with a second normally deenergized trip coil and being openable to disconnect said second bus from said second source upon energization of said second trip coil; third switching means for connecting said first electric power bus to said second electric power bus, said third switching means also being equipped with a third normally deenergized trip coil and being openable to disconnect said first bus from said second bus upon energization of said third trip coil; an electrical connection from said common neutral conductor to a point of alteRnating current ground potential; means including a first sensor inductively coupled to said electrical connection for generating a current to effect energization of said third trip coil upon the occurrence of a ground fault on one of said electric power buses; first normally disabled means including a second sensor inductively coupled to said common neutral conductor at a point intermediate said first alternating current energy source and said electrical connection for generating a current, when enabled, to effect energization of said first trip coil upon the occurrence of a ground fault on said first electric power bus; second normally disabled means including a third sensor inductively coupled to said common neutral conductor at a point intermediate said second alternating current energy source and said electrical connection for generating a current, when enabled, to effect energization of said second trip coil upon the occurrence of a ground fault on said second electric power bus; and with the generation of current to effect energization of said third trip coil also serving to enable said first and second normally disabled means.
Claim 3
Dependent Claim
22 words
The system as defined in claim 1 wherein said first, second and third switching means each comprise a multiphase circuit breaker assembly.
Claim 4
Dependent Claim
19 words
The system as defined in claim 1 wherein said first, second and third sensors each comprise a current transformer.
Claim 5
Dependent Claim
67 words
The system as defined in claim 1 wherein each of said current generating means effecting energization of a trip coil includes a relay circuit operable to generate a current of sufficient magnitude to energize its respective trip coil at a time later than the occurrence of a ground fault on one of said electric power buses by an amount proportionately related to the magnitude of said fault.
Claim 6
Dependent Claim
49 words
The system as defined in claim 4 wherein said first and second normally disabled means are disabled by a contact short circuiting the input terminals of the associated relay circuit and wherein said generation of current to effect energization of said third trip coil disconnects said short circuiting contact.
Claim 7
Dependent Claim
57 words
The system as defined in claim 5 wherein there is additionally included at least one multiphase alternating current feeder circuit coupled to one of said first and second electric power buses and to said common neutral conductor, and means for disabling said feeder circuit upon the occurrence of a ground fault on one of the conductors thereof.
Claim 8
Dependent Claim
55 words
The system as defined in claim 6 wherein the time lapse in disabling said feeder circuit upon the occurrence of a ground fault on one of the conductors thereof is less than the time lapse in disabling said third switching means upon the occurrence of a ground fault on one of said electric power buses.
Claim 9
Dependent Claim
65 words
The system as defined in claim 7 wherein the time lapse in disabling said third switching means upon the occurrence of a ground fault on one of said electric power buses is less than the time lapse in disconnecting said first and second buses from said first and second sources upon the occurrence of a ground fault on said first and second power buses, respectively.
Claim 10
Independent Claim
174 words
A system for detecting ground faults in a multistation, multiphase power distribution network having a common neutral conductor comprising: first and second multiconductor electric power buses; first and second switching means for respectively connecting said buses to two different sources of multiphase alternating current energy, with each switching means being openable to disconnect the associated bus and source; third switching means for interconnecting said buses, with said third switching means being openable to disconnect said buses; an electrical connection from said common neutral conductor to a point of alternating current ground potential; tie relaying means coupled to said third switching means and responsive to ground current flowing through said electrical connection for disabling said third switching meAns to disconnect said first and second buses; and first and second normally disabled relaying means coupled to said first and second switching means respectively, with each responsive to ground current flowing through said neutral conductor for disabling at least one of said first and second switching means in response to the disabling of said third switching means.
Claim 11
Independent Claim
174 words
A system for detecting ground faults in a multistation, multiphase power distribution network having a common neutral conductor comprising: first and second multiconductor electric power buses; first and second switching means for respectively connecting said buses to two different sources of multiphase alternating current energy, with each switching means being openable to disconnect the associated bus and source; third switching means for interconnecting said buses, with said third switching means being openable to disconnect said buses; an electrical connection from said common neutral conductor to a point of alternating current ground potential; tie relaying means coupled to said third switching means and responsive to ground current flowing through said electrical connection for disabling said third switching meAns to disconnect said first and second buses; and first and second normally disabled relaying means coupled to said first and second switching means respectively, with each responsive to ground current flowing through said neutral conductor for disabling at least one of said first and second switching means in response to the disabling of said third switching means.
References Cited (Backward Citations)
US3259802A
Cited
US3505566A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-01-25 | 1974-07-27 | 1975-01-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-01-25 | 1978-07-27 | 1979-01-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-01-25 | 1982-07-27 | 1983-01-26 | $7700.00 | Window Closed / Lapsed |