US3699431A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Selector circuit for determining faults in polyphase transmission systems
Assignee: English Electric Co Ltd
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Filing: 1969-12-10
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Granted: 1972-10-17
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Expires: 1989-12-10
Abstract
Abstract The invention provides a selector system for determining which phase or phases of a polyphase power transmission system are affected by a fault. The fault results in a fault current in the affected phase (phase-to-ground fault) or phases (phase-to-phase fault). To distinguish these changes from the existing phase currents due to normal loads, the quantities monitored are stored (phase and amplitude) and any changes in them are inspected to see whether a fault has occurred and, if so, what type of fault it is. Preferably, the ''''phase-to-phase'''' currents are the quantities monitored. The pattern of any substantial changes in these quantities establishes a fault pattern indicative of the nature of the fault. Means may also be provided for following developing faults. A measuring unit may be connected to the appropriate phase or phases following identification of the fault.
Inventors
- 👤 Eric Paddison
- 👤 Christopher George Wilson
- 👤 Frederick Martin Gray
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 03:23
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/44; H02H3/26; H02H3/32; H02H3/34
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
129 words
A selector circuit for determining faults in a polyphase transmission system, comprising means for monitoring electrical quantities associated with the various phases, means connected to the monitoring means for retaining pre-fault values of the quantities in terms of both amplitude and phase and including means for vectorially subtracting the pre-fault values of the quantities from the fault values of the quantities to produce signals indicative of the differences in amplitude and phase relation between the pre-fault and fault values of the quantities, control means connected to the signal producing means for establishing a fault pattern which is dependent on whether the individual signals are greater or less than a predetermined limit and means connected to the control means for identifying the type of fault from the fault pattern produced.
Claim 2
Dependent Claim
129 words
A selector circuit for determining faults in a polyphase transmission system, comprising means for monitoring electrical quantities associated with the various phases, means connected to the monitoring means for retaining pre-fault values of the quantities in terms of both amplitude and phase and including means for vectorially subtracting the pre-fault values of the quantities from the fault values of the quantities to produce signals indicative of the differences in amplitude and phase relation between the pre-fault and fault values of the quantities, control means connected to the signal producing means for establishing a fault pattern which is dependent on whether the individual signals are greater or less than a predetermined limit and means connected to the control means for identifying the type of fault from the fault pattern produced.
Claim 3
Dependent Claim
88 words
A selector circuit according to claim 1, wherein the signal producing means comprises a bridge having its output connected to the control means, the bridge having zero output when the quantities are vectorially constant and comprising a tuned circuit and a resistive component, whereby on the occurrence of a fault the voltage across the tuned circuit is related to the vector values of the quantities before the occurrence of the fault and the voltage across the resistive component is related to the existing vector values of the quantities.
Claim 4
Dependent Claim
57 words
A selected circuit according to claim 1, wherein the signals are applied to respective comparators together with a reference signal corresponding to the predetermined limit and equal to a predetermined fraction of the greatest of the signals plus a predetermined bias level, the outputs of the comparators being of binary digital form and forming the fault pattern.
Claim 5
Dependent Claim
52 words
A selector circuit according to claim 1, wherein the fault identifying means are adapted to cause a distance-to-fault measuring unit to be connected to the faulty phase or phases, and including a memory fed with the fault pattern and responsive to the operation of the measuring unit to hold the fault pattern.
Claim 6
Dependent Claim
55 words
A selector circuit according to claim 4, wherein on detection of a ''''line-to-ground'''' fault, said bias level is substantially raised to prevent load changes causing false selection and said predetermined fraction is substantially reduced to release the memory to allow detection of evolution of the ''''line-to-ground'''' fault to a ''''line-to-line'''' fault or a 3-phase fault.
Claim 7
Dependent Claim
15 words
A selector circuit according to claim 1, wherein the electrical quantities are the line-to-line currents.
Claim 8
Dependent Claim
63 words
A selector circuit according to claim 5, including a coincidence circuit having its input connected to the output of the fault identifying means and its output connected to the input of the memory and operative, when a ''''line-to-ground'''' fault is indicated and the fault pattern changes from a ''''line-to-ground'''' type to a ''''line-to-line'''' type, to enter the new fault pattern in the memory.
Claim 9
Dependent Claim
63 words
A selector circuit according to claim 5, including a logic circuit connected between the output from the fault identifying means and the input to the memory and operative, when a ''''line-to-ground'''' fault is indicated and the fault pattern changes to indicate another ''''line-to-ground'''' fault, to change the fault pattern in the memory to that indicating a ''''line-to-line'''' fault between the relevant two lines.
Claim 10
Dependent Claim
52 words
A selector circuit according to claim 1, including a set of excess current detector connected to the phases to indicate if the respective phase currents exceed a level at which the monitoring means begin to saturate, the fault pattern being replaced by the excess current pattern on any excess current being detected.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-17 | 1976-04-17 | 1976-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-17 | 1980-04-17 | 1980-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-17 | 1984-04-17 | 1984-10-17 | $7700.00 | Window Closed / Lapsed |