Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
2000-04-26
2003-07-08
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C702S060000, C702S061000, C702S064000, C702S032000, C702S108000, C702S182000
Reexamination Certificate
active
06591203
ABSTRACT:
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.
Other aspects of the invention are described below.
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Benco Joseph P.
Das Ratan
ABB Inc.
Hoff Marc S.
Tsai Carol S
Woodcock & Washburn LLP
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