Source: http://www.google.com/patents/US6591203
Timestamp: 2014-03-13 17:10:45
Document Index: 281288018

Matched Legal Cases: ['art 1', 'art 2', 'art 1', 'art 1', 'art 2', 'art 2']

Patent US6591203 - Fault locator for radial sub-transmission and distribution systems - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn improved fault location method may be used to locate faults associated with one or more conductors of an electric power transmission and distribution system. The method includes the steps of detecting a fault; determining whether pre-fault data are available and, if so, using the pre-fault data to...http://www.google.com/patents/US6591203?utm_source=gb-gplus-sharePatent US6591203 - Fault locator for radial sub-transmission and distribution systemsAdvanced Patent SearchPublication numberUS6591203 B1Publication typeGrantApplication numberUS 09/558,797Publication dateJul 8, 2003Filing dateApr 26, 2000Priority dateApr 26, 2000Fee statusPaidPublication number09558797, 558797, US 6591203 B1, US 6591203B1, US-B1-6591203, US6591203 B1, US6591203B1InventorsRatan Das, Joseph P. BencoOriginal AssigneeAbb, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (13), Referenced by (2), Classifications (11), Legal Events (7) External Links: USPTO, USPTO Assignment, EspacenetFault locator for radial sub-transmission and distribution systemsUS 6591203 B1Abstract An improved fault location method may be used to locate faults associated with one or more conductors of an electric power transmission and distribution system. The method includes the steps of detecting a fault; determining whether pre-fault data are available and, if so, using the pre-fault data to compute a load impedance and estimate the fault location using the computed load impedance; if pre-fault data are not available, determining whether pre-fault data are available in a first memory location and, if so, using the pre-fault data to compute a load impedance and estimate the fault location using the computed load impedance; and if pre-fault data are not available in the first memory location, using a pre-fault load impedance from a second memory location in estimating the fault location.
We claim: 1. An improved method for locating faults associated with one or more conductors of an electric power transmission and distribution system, wherein the method is employed in a system including a first memory location for use in storing present pre-fault data relating to a most recent fault condition, a second memory location for use in storing previous pre-fault data relating to a previous fault condition, and a third memory location for use in storing a default load impedance value, the method comprising:
(a) detecting a fault; (b) determining whether present pre-fault data are available in the first memory location and, if so, using the present pre-fault data to compute a load impedance and estimate the fault location using the computed load impedance; (c) if present pre-fault data are not available, determining whether previous pre-fault data are available in the second memory location and, if so, using the previous pre-fault data to compute a load impedance and estimate the fault location using the computed load impedance; and (d) if previous pre-fault data are not available in the second memory location, using the default load impedance from the third memory location in estimating the fault location. 2. A method as recited in claim 1, wherein the method is used to locate a fault in a radial sub-transmission and distribution system.
3. A method as recited in claim 1, further comprising the step of computing the default load impedance.
4. A method as recited in claim 3, wherein the default load impedance is computed using the following steps: a fault locator is powered up and a default load value is determined; a primary system voltage is computed based on a potential transformer ratio and configuration; a primary load impedance magnitude is computed; real and imaginary parts of the primary load impedance are computed using a default power factor; and the primary load impedance value is converted to secondary resistance and reactance values using the potential transformer ratios.
5. An improved system for locating faults associated with one or more conductors of an electric power transmission and distribution system, comprising:
a first memory location for use in storing present pre-fault data relating to a most recent fault condition, a second memory location for use in storing previous pre-fault data relating to a previous fault condition, and a third memory location for use in storing a default load impedance value; means for detecting a fault; means for determining whether present pre-fault data are available in the first memory location and for using the present pre-fault data, if available, to compute a load impedance and estimate the fault location using the computed load impedance; means determining whether previous pre-fault data are available in the second memory location, and for using the previous pre-fault data, if available, to compute a load impedance and estimate the fault location using the computed load impedance; and means for using the default load impedance from the third memory location in estimating the fault location, if previous pre-fault data are not available in the second memory location. 6. A system as recited in claim 5, wherein the system is used to locate a fault in a radial sub-transmission and distribution system.
7. A system as recited in claim 5, further comprising means for computing the default load impedance.
8. A system as recited in claim 7, wherein the means for computing the default load impedance comprises means for performing the following steps: determining a default load value; computing a primary system voltage based on a potential transformer ratio and configuration; computing a primary load impedance magnitude; computing real and imaginary parts of the primary load impedance; and converting the primary load impedance value to secondary resistance and reactance values.
FIELD OF THE INVENTION The present invention relates generally to the field of protective relaying, and more particularly to apparatus and methods for locating faults on an electrical transmission line.
BACKGROUND OF THE INVENTION The present invention is related to the invention described in U.S. Pat. No. 5,428,549, Jun. 27, 1995, titled �Transmission Line Fault Location System� (Chen), which is hereby incorporated by reference in its entirety. More particularly, the present invention provides an improvement that can be applied to radial sub-transmission and distribution systems in situations where pre-fault load information is not available. This situation is encountered during auto-reclosing and switch-into-fault situations. If the pre-fault load is below a pre-determined value, then for computing purposes it is considered to be absent. Under such situations, the algorithm described in the patent to Chen is inapplicable since it relies on the pre-fault information. The present invention seeks to provide a way to overcome this limitation by using available information and historical data.
SUMMARY OF THE INVENTION An improved fault location method may be used to locate faults associated with one or more conductors of an electric power transmission and distribution system. The method includes the steps of detecting a fault; determining whether pre-fault data are available and, if so, using the pre-fault data to compute a load impedance and estimate the fault location using the computed load impedance; if pre-fault data are not available, determining whether pre-fault data are available in a first memory location and, if so, using the pre-fault data to compute a load impedance and estimate the fault location using the computed load impedance; and if pre-fault data are not available in the first memory location, using a pre-fault load impedance from a second memory location in estimating the fault location.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically depicts, in a very simplified way, the algorithm disclosed by Chen in U.S. Pat. No. 5,428,549.
FIG. 2 schematically depicts an improved fault location algorithm for radial sub-transmission and distribution systems in accordance with the present invention.
FIG. 3 schematically depicts a process in accordance with the present invention for computing a default load impedance during a power up phase of a fault locator.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 2 depicts an improved fault locator algorithm for radial sub-transmission and distribution systems. This inventive algorithm works in the absence of pre-fault data, and is based on providing the pre-fault load information using historical data. The algorithm disclosed by U.S. Pat. No. 5,428,549, shown in FIG. 1, can be divided into two parts: Part 1 computes the load impedance and Part 2 calculates the fault location using the load impedance computed in Part 1 along with other information.
As shown in FIG. 2, according to the present invention, if the pre-fault data are available, then both Part 1 and Part 2 of Chen's algorithm are used and pre-fault information is saved into RAM memory location 1 for future use. However, if the pre-fault data are not available, then pre-fault data is copied into a pre-fault buffer from RAM memory location 1 saved from a previous fault. It is possible that pre-fault data may not be available in RAM memory location 1. There are two reasons for this: the fault locator may not have estimated a fault location or the fault locator may have been powered down before the present fault and thereby cleared the RAM memory location 1. In such a situation, pre-fault load impedance is picked up from RAM memory location 2, which has a default value of load impedance. Part 2 of the Chen's algorithm is then used. The fault locator computes the default pre-fault load impedance, based on user input, each time the unit is powered up.
Computation of the default pre-fault load impedance is illustrated in FIG. 3. As shown, this process entails the following steps. First, the fault locator is powered up and a default load value (for example, in units of MVa) is read. Next, a primary system voltage, based on the potential transformer ratio and configuration, is computed. A primary load impedance magnitude is then computed, and then the real and imaginary parts of the primary load impedance are computed using a default power factor (e.g., 0.8). The primary load impedance value is then converted to secondary resistance and reactance values using the current and potential transformer ratios.
In sum, the present invention provides apparatus and methods for locating faults on an electrical transmission line. The preferred embodiments described herein represent exemplary implementations of the invention. However, the scope of protection of the following claims is not intended to be limited to the specific embodiments disclosed herein.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4148087 *Apr 20, 1977Apr 3, 1979Phadke Arun GDistance relay for electric power transmission linesUS4766549 *Nov 30, 1984Aug 23, 1988Electric Power Research Institute, Inc.Single-ended transmission line fault locatorUS4812995 *May 19, 1987Mar 14, 1989Girgis Adly AAdaptive Kalman Filtering in fault classificationUS4972290 *Sep 29, 1989Nov 20, 1990Abb Power T & D Company Inc.Electric power system with remote monitoring and control of protective relaysUS4996624 *Sep 28, 1989Feb 26, 1991Schweitzer Engineering Laboratories, Inc.Fault location method for radial transmission and distribution systemsUS5428549May 28, 1993Jun 27, 1995Abb Power T&D CompanyTransmission line fault location systemUS5455776 *Sep 8, 1993Oct 3, 1995Abb Power T & D Company Inc.Automatic fault location systemUS5550751 *Oct 15, 1993Aug 27, 1996The Texas A & M University SystemExpert system for detecting high impedance faultsUS5661664 *Aug 15, 1995Aug 26, 1997Abb Power T&D Company Inc.One-terminal data fault location system and process for locating a faultUS5773980 *Jan 30, 1997Jun 30, 1998Abb Power T&D Company, Inc.One-terminal fault location system that corrects for fault resistance effectsUS5839093 *Dec 31, 1996Nov 17, 1998Abb Transmit OySystem for locating faults and estimating fault resistance in distribution networks with tapped loadsUS5956220 *Feb 5, 1998Sep 21, 1999Abb Network Partner AbAdaptive distance protection systemUS6307723 *Jun 16, 1999Oct 23, 2001Alstom Uk Ltd.Parallel-feeder directional overcurrent protection* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS6904549 *Aug 8, 2002Jun 7, 2005Siemens AktiengesellschaftMethod for fault identification in an electrical radial network, an application of the method and an arrangement for fault identification in an electrical radial networkUS8269503Apr 16, 2008Sep 18, 2012Hydro-QuebecElectrical network fault location by distributed voltage measurements* Cited by examinerClassifications U.S. Classification702/58, 702/32, 702/60, 702/108, 702/182, 702/64, 702/61International ClassificationG01R31/08Cooperative ClassificationG01R31/085, G01R31/088European ClassificationG01R31/08FLegal EventsDateCodeEventDescriptionJan 18, 2011FPAYFee paymentYear of fee payment: 8Jan 18, 2011SULPSurcharge for late paymentYear of fee payment: 7Mar 13, 2007SULPSurcharge for late paymentMar 13, 2007FPAYFee paymentYear of fee payment: 4Jan 24, 2007REMIMaintenance fee reminder mailedMay 5, 2003ASAssignmentOwner name: ABB INC., CONNECTICUTFree format text: MERGER;ASSIGNOR:ABB AUTOMATION, INC.;REEL/FRAME:014020/0733Effective date: 20011031Owner name: ABB INC. 501 MERRITT 7NORWALK, CONNECTICUT, 06851Sep 11, 2000ASAssignmentOwner name: ABB AUTOMATION INC., OHIOFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:DAS, RATAN;BENCO, JOSEPH P.;REEL/FRAME:011096/0515Effective date: 20000901Owner name: ABB AUTOMATION INC. 29801 EUCLID AVENUE WICKLIFFERotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google