US3633071A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Differential protective circuit
Assignee: Siemens AG
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Filing: 1970-11-06
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Granted: 1972-01-04
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Expires: 1990-11-06
Abstract
Abstract The outputs of a system to be protected are connected to current transformers. A summing circuit is connected to the secondary winding of the current transformers and produces the algebraic sum of the currents flowing in the system to be protected and provides an electrical magnitude derived from such sum to an indicator. The indicator produces an output signal which controls circuit breakers or the like in order to disconnect the system to be protected.
Inventors
- 👤 Alfons Fendt
- 👤 Eckart Maenicke
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:49
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/28; H02H3/283; H02H3/50; H02H3/52
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
221 words
A differential protective circuit for a system to be protected comprising a plurality of saturable current transformers having secondary windings and primary windings connected to outputs of the system to be protected; summing means connected to the secondary windings of the current transformers for producing the algebraic sum of the currents flowing into the system to be protected and providing an electrical magnitude in accordance with said sum; indicator means having an input electrically connected to the summing means and an output for providing an output signal at its output for disconnecting the system to be protected from a power supply in accordance with said electrical magnitude; circuit means connected to the secondary windings of the current transformers for indicating transformer saturation and including limit circuit means; a first circuit switch connected to the output of the indicator means for controlling the provision of the output signal of said indicator means for disconnecting the system to be protected; and first switch control means connected to the limit circuit means of said circuit means for controlling the conductivity condition of the first circuit switch, said first switch control means including OR gate means connected between said limit circuit means and said first circuit switch for switching said first circuit switch to its nonconductive condition when one of said current transformers becomes saturated.
Claim 2
Dependent Claim
221 words
A differential protective circuit for a system to be protected comprising a plurality of saturable current transformers having secondary windings and primary windings connected to outputs of the system to be protected; summing means connected to the secondary windings of the current transformers for producing the algebraic sum of the currents flowing into the system to be protected and providing an electrical magnitude in accordance with said sum; indicator means having an input electrically connected to the summing means and an output for providing an output signal at its output for disconnecting the system to be protected from a power supply in accordance with said electrical magnitude; circuit means connected to the secondary windings of the current transformers for indicating transformer saturation and including limit circuit means; a first circuit switch connected to the output of the indicator means for controlling the provision of the output signal of said indicator means for disconnecting the system to be protected; and first switch control means connected to the limit circuit means of said circuit means for controlling the conductivity condition of the first circuit switch, said first switch control means including OR gate means connected between said limit circuit means and said first circuit switch for switching said first circuit switch to its nonconductive condition when one of said current transformers becomes saturated.
Claim 3
Dependent Claim
112 words
A differential protective circuit as claimed in claim 1, wherein said circuit means comprises a plurality of integrating circuits each connected to the secondary winding of a corResponding one of the current transformers and a plurality of limit circuits each connected to a corresponding one of the integrating circuits whereby each of the current transformers provides a corresponding one of the integrating stages with an electrical magnitude proportional to the voltage of the secondary winding thereof, each of the limit circuits of said circuit means having a response magnitude adjusted in accordance with the permissible limit value of the voltage integral relative to time and determined by the onset of transformer saturation.
Claim 4
Dependent Claim
44 words
A differential protective circuit as claimed in claim 2, wherein said circuit means includes a plurality of filters each connected between the secondary winding of a corresponding one of the current transformers and a corresponding one of the limit circuits for filtering out harmonics.
Claim 5
Dependent Claim
138 words
A differential protective circuit as claimed in claim 2, further comprising additional circuit means connected to the secondary windings of the current transformers for differentiating signals in said secondary windings, said additional circuit means including additional limit circuit means, a second circuit switch connected between the summing means and the input of the indicator means for controlling the provision of said electrical magnitude to said indicator means, and second switch control means connected to the limit circuit means of said additional circuit means for controlling the conductivity condition of said second circuit switch, said second switch control means including additional OR gate means connected between said limit circuit means and said second circuit switch for switching said second circuit switch to its conductive condition in accordance with the differential quotient of the secondary current of the current transformers.
Claim 6
Dependent Claim
51 words
A differential protective circuit as claimed in claim 4, wherein said additional circuit means comprises a plurality of differentiating circuits each connected to the secondary winding of a corresponding one of the current transformers and a plurality of additional limit circuits each connected to a corresponding one of the differentiating circuits.
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) | 1975-01-03 | 1975-07-05 | 1976-01-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-03 | 1979-07-05 | 1980-01-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-03 | 1983-07-05 | 1984-01-04 | $7700.00 | Window Closed / Lapsed |