Patent US5115226A successfully refreshed from Google Patents.
US5115226A
Expired / Lapsed
US
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Relay for detecting a current disturbance and asserting an output
Assignee: Schweitzer Engineering Laboratories Inc
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Filing: 1989-10-12
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Granted: 1992-05-19
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Expires: 2009-10-12
Abstract
Abstract An apparatus for detecting a power system disturbance. The apparatus may be a current rate-of-change relay for qualifying system-separation transfer-trip commands.
Inventors
- 👤 Edmund O. Schweitzer, III
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 10:48
CPC Classifications
H; H02; H02H; H02H1/00; H02H1/0061; H02H1/04; H02H3/00; H02H3/006
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
119 words
An apparatus for detecting a power system disturbance, comprising: means for receiving at least one phase current or a residual current of a power system; means for scaling down said current; means for filtering and sampling said current; means for converting said current to digital data, and digital filter means for removing selected components from said digital data; means for determining the rate of change of said current, said determining means including means for determining a phasor difference between the present value of said current and a value of said current at a predetermined earlier time; means for comparing said rate of change to a predetermined value; and means for asserting an output if said predetermined value is exceeded.
Claim 2
Independent Claim
119 words
An apparatus for detecting a power system disturbance, comprising: means for receiving at least one phase current or a residual current of a power system; means for scaling down said current; means for filtering and sampling said current; means for converting said current to digital data, and digital filter means for removing selected components from said digital data; means for determining the rate of change of said current, said determining means including means for determining a phasor difference between the present value of said current and a value of said current at a predetermined earlier time; means for comparing said rate of change to a predetermined value; and means for asserting an output if said predetermined value is exceeded.
Claim 3
Dependent Claim
13 words
The apparatus of claim 1 wherein said filtering means includes an analog filter.
Claim 4
Dependent Claim
22 words
The apparatus of claim 2 wherein said analog filter is a two-pole lowpass filter having a cutoff frequency of about 85 HZ.
Claim 5
Dependent Claim
15 words
The apparatus of claim 2 wherein said digital filter means removes DC and ramp components.
Claim 6
Dependent Claim
15 words
The apparatus of claim 2 wherein said digital filter means is a double differentiator-smoother filter.
Claim 7
Dependent Claim
15 words
The apparatus of claim 1 wherein said current is sampled four times per system cycle.
Claim 8
Dependent Claim
74 words
The apparatus of claim 1 wherein said comparing means includes means for comparing said phasor difference to a predetermined threshold setting such that a time-delay dropout timer means is asserted if said phasor difference exceeds said threshold setting or a predetermined value of said current and remains asserted until said phasor difference stays below said threshold setting or said predetermined value for a period of time equal to the setting of a timer means.
Claim 9
Dependent Claim
29 words
The apparatus of claim 7 further including means for separating one power system from another if a separation signal is received during the time said timer means is asserted.
Claim 10
Independent Claim
13 words
The apparatus of claim wherein said receiving means receives all three phase currents.
Claim 11
Dependent Claim
18 words
The apparatus of claim 9 further including means for summing said phase currents to determine said residual current.
Claim 12
Dependent Claim
15 words
The apparatus of claim 1 which uses programmable-mask logic for detection a power system disturbance.
Claim 13
Dependent Claim
33 words
The apparatus of claim 1 further including means for separating a first power system from a second power system if a system separation signal is received during the time said output is asserted.
Claim 14
Independent Claim
141 words
A method for detecting a power system disturbance, comprising: receiving at least one phase current or a residual current of a power system; scaling down said current; filtering and sampling said current; converting said current to digital data; removing DC and ramp components from said digital data; determining a phasor difference between the present value of said current and a value of said current at a predetermined earlier time; comparing said phasor difference to a predetermined threshold setting and asserting a time-delay dropout timer means if said phasor difference exceeds said threshold setting or a predetermined value of said current wherein said timer remains asserted until said phasor difference stays below said threshold setting or said predetermined value for a period of time equal to the setting of said timer means; and asserting an output if said predetermined value is exceeded.
Claim 15
Independent Claim
141 words
A method for detecting a power system disturbance, comprising: receiving at least one phase current or a residual current of a power system; scaling down said current; filtering and sampling said current; converting said current to digital data; removing DC and ramp components from said digital data; determining a phasor difference between the present value of said current and a value of said current at a predetermined earlier time; comparing said phasor difference to a predetermined threshold setting and asserting a time-delay dropout timer means if said phasor difference exceeds said threshold setting or a predetermined value of said current wherein said timer remains asserted until said phasor difference stays below said threshold setting or said predetermined value for a period of time equal to the setting of said timer means; and asserting an output if said predetermined value is exceeded.
Claim 16
Dependent Claim
22 words
The method of claim 13 further including receiving all three phase currents and summing said phase currents to determine said residual current.
Claim 17
Dependent Claim
31 words
The method of claim 13 further including separating a first power system from a second power system if a system separation signal is received during the time said output is asserted.
Claim 18
Independent Claim
96 words
An apparatus for detecting a power system disturbance, comprising: means for receiving at least one phase current or a residual current of a power system; means for converting the current into a current phasor; means for determining the rate of change of said current phasor, said determining means includes means for determining a phasor difference between the present value of said current and a value of said current of a predetermined earlier time; means for comparing the rate of change to a predetermined value; and means for asserting an output if the predetermined value is exceeded.
Claim 19
Independent Claim
96 words
An apparatus for detecting a power system disturbance, comprising: means for receiving at least one phase current or a residual current of a power system; means for converting the current into a current phasor; means for determining the rate of change of said current phasor, said determining means includes means for determining a phasor difference between the present value of said current and a value of said current of a predetermined earlier time; means for comparing the rate of change to a predetermined value; and means for asserting an output if the predetermined value is exceeded.
Claim 20
Dependent Claim
15 words
The apparatus of claim 16 further including means for scaling down and sampling said current.
Claim 21
Dependent Claim
27 words
The apparatus of claim 17 further including means for converting said current to digital data and digital filter means for removing selected components from said digital data.
Claim 22
Independent Claim
73 words
A method for detecting a power system disturbance, comprising: receiving at least one phase current or a residual current of a power system; converting the current into a current phasor; determining a phasor difference between the present value of said phasor current and a value of said phasor current of a predetermined earlier time; comparing the rate of change to a predetermined value; and asserting an output if the predetermined value is exceeded.
Claim 23
Independent Claim
73 words
A method for detecting a power system disturbance, comprising: receiving at least one phase current or a residual current of a power system; converting the current into a current phasor; determining a phasor difference between the present value of said phasor current and a value of said phasor current of a predetermined earlier time; comparing the rate of change to a predetermined value; and asserting an output if the predetermined value is exceeded.
Claim 24
Dependent Claim
22 words
The method of claim 19 further including receiving all three phase currents and summing said phase currents to determine said residual current.
Claim 25
Dependent Claim
31 words
The method of claim 20 further including separating a first power system from the second power system if a system separation signal is received during the time said output is asserted.
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) | 1995-05-19 | 1995-11-18 | 1996-05-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-05-19 | 1999-11-18 | 2000-05-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-05-19 | 2003-11-18 | 2004-05-19 | $7700.00 | Window Closed / Lapsed |