Data processing: structural design – modeling – simulation – and em – Simulating electronic device or electrical system – Power system
Reexamination Certificate
1998-12-22
2001-11-20
Teska, Kevin J. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Simulating electronic device or electrical system
Power system
C703S017000
Reexamination Certificate
active
06321187
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to computer aided engineering tools, and more particularly, the present invention relates to a tool for assessing the reliability of an electrical power system.
BACKGROUND OF THE INVENTION
The typical determination of reliability of a system is straightforward yet potentially very time-intensive. To assess the reliability of a system one needs only to identify the total different possible states of the system (with respect to the operational status of each component), determine which of these states result in the failure of the specific system, calculate the probabilities of each of these failure states occurring, and sum them to arrive at the overall reliability.
In the case of an electrical power system, a failure of the system is generally considered to be loss of power to a particular load, e.g., a starting motor, a load bus, etc. The task of assessing the reliability of an electrical power system is formidable because there are ordinarily several components to the system, and with each component having at least two possible states, operational or non-operational there are at least 2 raised to the power of the number of total system components possible states. In even a modest electrical power system the number of components could be 20 or more, which establish a total number of possible states in excess of 1 million.
More than simply assessing the reliability of a single system, system designers and engineers typically wish to evaluate several system designs. Having to assess millions of possible operational states for each system design is time and cost prohibitive.
Computer added engineering tools have been available for a number of different applications. For example U.S. Pat. No. 4,847,795 discusses a system for diagnosing defects in electronic assemblies. Actual test data is gathered and analyzed to determine failure patterns, which are used to estimate failure probabilities given certain constraint conditions.
In U.S. Pat. No. 5,138,694 a qualitative reasoning approach is applied to observed failure symptoms to identify the reasons for a particular failure. The system does not contemplate predicting failures, and instead focuses on determining failure causes and employs a fault tree analysis approach.
The disclosure of U.S. Pat. No. 5,144,563 is directed to a system to aid in the design of computer chips, and more particularly, to reducing wiring lengths between components. Similarly, U.S. Pat. No. 5,257,201 discloses a system that attempts to reduce the number of connections in an integrated circuit. And, Japanese patent no. 59-184969 discloses use of the “minimum cut” method to optimize integrated circuit design, again by reducing wiring lengths.
In U.S. Pat. No. 5,293,585 an expert system is disclosed apart from any particular application. The expert system implements a rule-based reasoning approach to failure analysis and fault detection.
U.S. Pat. No. 5,386,498 also describes an expert system capable of drawing conclusions based on experience. Knowledge bases are built and updated through a proposed process.
An article appearing in the July, 1986 issue of Computer magazine discusses a system for troubleshooting failed electronics using artificial intelligence. The system uses a fault detection and isolation approach to identify a failed hardware device within a larger system.
It is clear numerous computer based systems and methods are available to assist in the design of electrical systems and components. However, there remains a need for a tool for quickly evaluating the reliability of system designs, and particularly power distribution system designs and variations and alternatives thereto.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a method for assessing the reliability of an electrical power distribution system begins with identifying each element of the electrical power distribution system, and establishing characteristic data for each of these elements. The characteristic data at least identifies one operating characteristic of the element and further identifies interconnections of that element to other elements in the system. Next, at least one “minimum cut” is determined separating a first system element from a second system element, e.g., a power source from a load. The minimum cut is at least based upon the interconnection data. At least one third element is then identified, located on the minimum cut, and the reliability may then be assessed by evaluating the characteristic data of the at least one third element.
Additionally, the method may include identifying a plurality of elements on the minimal cut, and assessing reliability of the system based at least upon the characteristic data associated with each of the plurality of elements.
REFERENCES:
patent: 4847795 (1989-07-01), Baker et al.
patent: 5138694 (1992-08-01), Hamilton
patent: 5144563 (1992-09-01), Date et al.
patent: 5224057 (1993-06-01), Igarashi et al.
patent: 5257201 (1993-10-01), Berman et al.
patent: 5293585 (1994-03-01), Morita
patent: 5386498 (1995-01-01), Kakefuda
patent: 6125453 (2000-09-01), Wyss
patent: 59-184969 (1984-10-01), None
patent: 3-201033 (1991-09-01), None
Wjyss et al.; “Probabilistic logic modeling of network reliability for hybrid network architectures”: IEE Conf. Local Computer Networks; pp. 404-413, Oct. 1996.*
El-Sayed et al.; “Fuzzy sets for reliability assessment of electric power distribution systems”;IEEE Proc. Circuits and Systems; pp. 1491-1494, Aug. 1994.*
Sharaf et al.; Reliability evaluation in power-system transmission planning: practical considerations; pp. 274-279, Aug. 1988.*
Elliot; “Computer-assisted fault-tree construction using a knowledge-based approach”; IEEE Trans. Reliability; pp. 112-120, Mar. 1994.*
Alexopoulos;“A note on state-space decomposition methods for analyzing stochastic flow networks”; IEEE Trans. Reliability; pp. 354-357, Jun. 1995.*
Kishimoto; “Reliable flow with failures in a network”; IEEE Trans. Reliability; pp. 308-315, Sep. 1997.
Henderson Eric A.
Squier Steven E.
Hamilton Sundstrand Corporation
Jones Hugh
Marshall O'Toole Gerstein Murray & Borun
Teska Kevin J.
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