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US4591992A
Expired / Lapsed
US
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Method and system for identifying the direction of a fault in a power line
Assignee: Toshiba Corp
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Filing: 1983-12-23
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Granted: 1986-05-27
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Expires: 2003-12-23
Abstract
Abstract In direction identification for a close-in fault when the voltage becomes very small, direction of the fault is determined from the discriminant D given by: D=V.sub.k1 i.sub.k2 -V.sub.k3 i.sub.k4 where V k1 , V k3 represent sample values of the voltage at time points k1, k3, and i k2 , i k4 represent either sample values of the current at time points k2, k4 or such sample values minimum current component values corresponding to pre-fault power flow. Here, k1=n-m-M; k2=n; k3=n-m; k4=n-M, where m represents the number of sampling operations over an interval equal to a multiple of half cycle of the system frequency, M represents an integer, and n represents a sampling time point. A signal for use, e.g., as a condition for tripping a circuit breaker is produced when the fault is found to be in the direction of the protection zone.
Inventors
- 👤 Mitsuru Yamaura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 10:47
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/08; H02H3/081; H02H3/38
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
216 words
A direction identification method for identifying the direction of a close-in fault, comprising the steps of: (a) sampling a voltage and a current; (b) judging whether or not the voltage is less than a predetermined threshold; (c) determining the direction of a fault in accordance with the polarity of a discriminant D given by: D=V.sub.k1 i.sub.k2 -v.sub.k3 i.sub.k4 where v kj (j-1 or 3) represents a sample value of the voltage at a sampling time point kj, i kj (j=2 or 4) represents a value which is a function of a sample value of the current at a sampling time point kj, and k1=n-m-M k2=n k3=n-m k4=n-M where m represents an integer equal to the number of sampling operations over an interval equal to a multiple of a half cycle of the system frequency, M represents an interger, and n represents a sampling time point; wherein the determination of the direction in accordance with the polarity of the discriminant D is made for sampling time points n within a predetermined time interval from occurrence of a fault; and (d) producing, when the voltage is less than said predetermined threshold and the fault is found to be within a direction of a protection zone, a signal for use as a condition for triggering a fault responsive device.
Claim 2
Dependent Claim
216 words
A direction identification method for identifying the direction of a close-in fault, comprising the steps of: (a) sampling a voltage and a current; (b) judging whether or not the voltage is less than a predetermined threshold; (c) determining the direction of a fault in accordance with the polarity of a discriminant D given by: D=V.sub.k1 i.sub.k2 -v.sub.k3 i.sub.k4 where v kj (j-1 or 3) represents a sample value of the voltage at a sampling time point kj, i kj (j=2 or 4) represents a value which is a function of a sample value of the current at a sampling time point kj, and k1=n-m-M k2=n k3=n-m k4=n-M where m represents an integer equal to the number of sampling operations over an interval equal to a multiple of a half cycle of the system frequency, M represents an interger, and n represents a sampling time point; wherein the determination of the direction in accordance with the polarity of the discriminant D is made for sampling time points n within a predetermined time interval from occurrence of a fault; and (d) producing, when the voltage is less than said predetermined threshold and the fault is found to be within a direction of a protection zone, a signal for use as a condition for triggering a fault responsive device.
Claim 3
Dependent Claim
33 words
A method according to claim 1, wherein said integer m is equal to the number of sampling operations over an interval equal to a multiple of a full cycle of the system frequency.
Claim 4
Dependent Claim
11 words
A method according to claim 2, wherein said multiple is 1.
Claim 5
Dependent Claim
35 words
A method according to claim 1, wherein said integer m is equal to the number of sampling operations over an interval equal to an odd number multiple of a half cycle of the system frequency.
Claim 6
Dependent Claim
11 words
A method according to claim 4, wherein said multiple is 1.
Claim 7
Dependent Claim
42 words
A method according to claim 1, wherein said difference value is used as said value i kj and a sample value at a sampling time point of n-m is used as said value of a current component corresponding to prefault power flow.
Claim 8
Dependent Claim
70 words
A method according to claim 1, further comprising the step of prolonging, for a certain time interval, the production of said signal at said step (d), once the fault is found to be in the direction of the protection zone at said step (c) even if it is found thereafter that the voltage is not very small or that the fault is not in the direction of the protection zone.
Claim 9
Dependent Claim
68 words
A method according to claim 1, wherein the judgement at said step (b) is made using a sampled instantaneous value of the voltage, and the determination of the direction in accordance with the polarity of the discriminant D at said step (c) is made for sampling time points n within a certain time interval from the time when the sampled instantaneous value of the voltage becomes very small.
Claim 10
Dependent Claim
82 words
A method according to claim 1, wherein the polarity of the discriminant D is successively determined and stored in time sequence, and the determination of the direction in accordance with the polarity at said step (c) is initiated, when the voltage is found to be very small at said step (b), and is performed by referring to the stored polarities determined for the sampling time points n within a certain time interval from an estimated time point of occurrence of a fault.
Claim 11
Dependent Claim
21 words
A method according to claim 9, wherein the judgement at said step (b) is made using an amplitude of the voltage.
Claim 12
Dependent Claim
39 words
A method according to claim 1 wherein i kj represents a difference value obtained by subtracting a value of a current component corresponding to pre-fault power flow from the sample value of the current at the sampling point kj.
Claim 13
Dependent Claim
40 words
A method according to claim 1 wherein said predetermined time is less than the time required for the polarity of said determinant to change such that the polarity of said determinant used for determining fault direction is an initial value.
Claim 14
Dependent Claim
211 words
A direction identification system for identifying the direction of a close-in fault, comprising: (a) means for sampling a voltage and a current; (b) means for judging whether or not the voltage is less than a predetermined threshold (c) means for determining the direction of a fault in accordance with the polarity of a discriminant D given by: D=v.sub.k1 i.sub.k2 -v.sub.k3 i.sub.k4 where v kj (j=1 or 3) represents a sample value of the voltage at a sampling time point kj, i kj (j=2 or 4) represents a value which is a function of a sample value of the current at a sampling time point kj, and k1=n-m-M k2=n k3=n-m k4=n-M where m represents an integer equal to the number of sampling operations over an interval equal to a multiple of a half cycle of the system frequency, M represents an integer, and n represents a sampling time point; wherein the determining means determines the direction for sampling time points n within a predetermined time interval from occurrence of a fault; and (d) means for producing, when the voltage is less than said predetermined threshold and the fault is found to be within a direction of a protection zone, a signal for use as a condition for triggering a fault responsive device.
Claim 15
Dependent Claim
211 words
A direction identification system for identifying the direction of a close-in fault, comprising: (a) means for sampling a voltage and a current; (b) means for judging whether or not the voltage is less than a predetermined threshold (c) means for determining the direction of a fault in accordance with the polarity of a discriminant D given by: D=v.sub.k1 i.sub.k2 -v.sub.k3 i.sub.k4 where v kj (j=1 or 3) represents a sample value of the voltage at a sampling time point kj, i kj (j=2 or 4) represents a value which is a function of a sample value of the current at a sampling time point kj, and k1=n-m-M k2=n k3=n-m k4=n-M where m represents an integer equal to the number of sampling operations over an interval equal to a multiple of a half cycle of the system frequency, M represents an integer, and n represents a sampling time point; wherein the determining means determines the direction for sampling time points n within a predetermined time interval from occurrence of a fault; and (d) means for producing, when the voltage is less than said predetermined threshold and the fault is found to be within a direction of a protection zone, a signal for use as a condition for triggering a fault responsive device.
Claim 16
Dependent Claim
33 words
A system according to claim 13, wherein said integer m is equal to the number of sampling operations over an interval equal to a multiple of a full cycle of the system frequency.
Claim 17
Dependent Claim
11 words
A system according to claim 14, wherein said multiple is 1.
Claim 18
Dependent Claim
35 words
A system according to claim 13, wherein said integer m is equal to the number of sampling operation over an interval equal to an odd number multiple of a half cycle of the system frequency.
Claim 19
Dependent Claim
11 words
A system according to claim 16, wherein said multiple is 1.
Claim 20
Dependent Claim
42 words
A system according to claim 13, wherein said difference value is used as said value i kj and a sample value at a sampling time point of n-m is used as said value of a current component corresponding to pre-fault power flow.
Claim 21
Dependent Claim
68 words
A system according to claim 13, further comprising means for prolonging, for a certain time interval, production of said signal by said means (d), once the fault is found to be in the direction of the protection zone by said means (c) even if it is found thereafter that the voltage is not very small or that the fault is not in the direction of the protection zone.
Claim 22
Dependent Claim
61 words
A system according to claim 13, wherein said means (b) makes the judgement using a sampled instantaneous value of the voltage, and said means (c) determines the direction in accordance with the polarity of the discriminant D for sampling time points n within a certain time interval from the time when the sampled instantaneous value of the voltage becomes very small.
Claim 23
Dependent Claim
90 words
A system according to claim 13, wherein said means (c) comprises means for successively determining the polarity of the discriminant D, said system further comprising means for storing the determined polarity in time sequence, and wherein said means (c) begins, when the voltage is found to be very small by said means (b), the determination of the direction and conducts such determination by referring to the stored polarities determined for the sampling time points n with a certain time interval from an estimated time point of occurrence of a fault.
Claim 24
Dependent Claim
19 words
A system according to claim 21, wherein said means (b) makes the judgement using an amplitude of the voltage.
Claim 25
Dependent Claim
39 words
A system according to claim 13 wherein i kj represents a difference value obtained by subtracting a value of a current component corresponding to pre-fault power flow from the sample value of the current at the sampling point kj.
Claim 26
Dependent Claim
40 words
A system according to claim 13 wherein said predetermined time is less than the time required for the polarity of said determinant to change such that the polarity of said determinant used for determining fault direction is an initial value.
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) | 1989-05-26 | 1989-11-25 | 1990-05-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-05-26 | 1993-11-25 | 1994-05-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-05-26 | 1997-11-25 | 1998-05-27 | $7700.00 | Window Closed / Lapsed |