US3573552A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High-impedance, percentage-stabilized busbar differential protection
Assignee: ABB Norden Holding AB
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Filing: 1969-03-27
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Granted: 1971-04-06
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Expires: 1989-03-27
Abstract
Abstract A relay device operating in response to abnormal conditions in a line includes an arrangement for deriving from the line a current proportional to the current in the line. One terminal of this current deriving device is connected to the midpoint of a pair of rectifiers connected in series. The other terminal is connected to the midpoint between resistances of equal value connected in series with the pair of rectifiers. In the connection between the midpoint of the resistances and the terminal of the current deriving device is arranged the primary of a transformer. The secondary of this transformer through a full-wave rectifier feeds the relay in parallel with a resistance. The arrangement is such that the relay is fed with the difference between the voltage across the latter resistance and the voltage across the two equal resistances.
Inventors
- 👤 Thorleif Forfod
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 05:03
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/28; H02H3/283
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
200 words
Percentage differential protection device for electric bus bars to which a number of feeders are connected, said protection device comprising a relay having two terminals, means for operating said relay in response to abnormal conditions in said feeders comprising means for deriving from each of said feeders a current proportional to the current therein, said current deriving means having first and second terminals, a pair of rectifying means for each of said feeders connected in series and a connection between the first of said terminals and the midpoint of said rectifying means, first and second resistors of equal value connected in parallel with said pairs of rectifiers, a connection between the midpoint of said first and second resistors and the second terminals of said current deriving means, means associated with said last connection to derive therefrom a direct current proportional to the current therein, means connecting the end of one of the first resistors remote from said midpoint to one terminal of said relay, means including a third resistor connecting the end of the second resistor remote from said midpoint to the other terminal of the relay, said third resistor being connected in parallel with said direct current deriving means.
Claim 2
Dependent Claim
200 words
Percentage differential protection device for electric bus bars to which a number of feeders are connected, said protection device comprising a relay having two terminals, means for operating said relay in response to abnormal conditions in said feeders comprising means for deriving from each of said feeders a current proportional to the current therein, said current deriving means having first and second terminals, a pair of rectifying means for each of said feeders connected in series and a connection between the first of said terminals and the midpoint of said rectifying means, first and second resistors of equal value connected in parallel with said pairs of rectifiers, a connection between the midpoint of said first and second resistors and the second terminals of said current deriving means, means associated with said last connection to derive therefrom a direct current proportional to the current therein, means connecting the end of one of the first resistors remote from said midpoint to one terminal of said relay, means including a third resistor connecting the end of the second resistor remote from said midpoint to the other terminal of the relay, said third resistor being connected in parallel with said direct current deriving means.
Claim 3
Dependent Claim
45 words
Percentage differential protection device as claimed in claim 1 in which said third resistor and said direct current deriving means coNstitute a differential circuit, and in which said direct current deriving means comprises a transformer, and said first and second resistors constitute a stabilizing circuit.
References Cited (Backward Citations)
US2608606A
Cited
US3492533A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-05 | 1974-10-05 | 1975-04-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-05 | 1978-10-05 | 1979-04-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-05 | 1982-10-05 | 1983-04-06 | $7700.00 | Window Closed / Lapsed |