Showing papers by "Chen-Ching Liu published in 1991"
TL;DR: In this paper, the authors proposed a methodology for maintaining rule-based expert systems, detecting the relations of conflict, redundancy and maintaining consistency of the rule base, tracing the reasoning process to understand the problem solving approach, and reducing the size of test cases after changes are made to the rules.
Abstract: CRAFT (customer restoration and fault testing) is a rule-based expert system capable of locating the faulted section of a power transmission line based on the status of circuit breakers an automatic switches. CRAFT has been operating online in the Puget Sound Power and Light control center since July 1988. The online operational experience is reported. Many of the developed expert systems will be maintained or modified by utility engineers. This study proposes a methodology for maintaining rule-based expert systems. The following capabilities are incorporated: detecting the relations of conflict, redundancy, etc., to maintain consistency of the rule base, tracing the reasoning process to understand the problem solving approach, and reducing the size of test cases after changes are made to the rules. The proposed method has been implemented for CRAFT. >
57 citations
TL;DR: An expert system called RETEX (relay testing expert) has been developed as a computer aid for analysis of relay testing data and a relay logic model is used to determine the expected relay operation for simulated faults.
Abstract: A new expert system application to power system protective relay evaluation testing, a crucial but time-consuming engineering task, is presented. An expert system called RETEX (relay testing expert) has been developed as a computer aid for analysis of relay testing data. A knowledge base for relay testing data analysis has been developed. A relay logic model is used to determine the expected relay operation for simulated faults. Hierarchical test reports and comparison reports can be automatically generated by RETEX, which is designed with basic language processing capabilities. The generality necessary for handling various relay models is provided by a description file approach. The expert system is implemented in a rule-based and object-oriented architecture with the expert system development tool NEXPERT Object. The feasibility of the prototype has been demonstrated with Bonneville Power Administration (BPA) relay testing data. >
12 citations
TL;DR: The capabilities of CRAFT are extended by adding two new knowledge bases with rules to determine the status of unsupervised automatic switches and to detect the presence and location of a manual switch with an incorrect status following a fault.
Abstract: The implementation and operation of an expert system in a control center environment is discussed. CRAFT (customer restoration and fault testing) is a rule-based expert system which is capable of locating the faulted section of a transmission line equipped with automatic switches and circuit breakers. In this study, the capabilities of CRAFT are extended by adding two new knowledge bases with rules to determine the status of unsupervised automatic switches and to detect the presence and location of a manual switch with an incorrect status, following a fault. An approach to appending a separate expert system computer to the SCADA system is developed. Software and hardware interfaces are designed and implemented. The completed implementation is operating online. The implementation represents a step toward practical application of expert systems for real time operation of power systems. >
11 citations
24 Jun 1991
TL;DR: In this article, a parameter estimation algorithm to aid power converter designers in fine-tuning the performance of switching DC power supplies is described. The estimation algorithm is incorporated with a fast time-domain circuit simulator to form a user friendly design environment.
Abstract: A parameter estimation algorithm to aid power converter designers in fine-tuning the performance of switching DC power supplies is described. This algorithm identifies the optimal parameter values which satisfy the design specifications. The estimation algorithm is incorporated with a fast time-domain circuit simulator to form a user-friendly design environment. Numerical results are provided. The estimation algorithm is general and can be applied to other types of converter design. >
3 citations