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An intelligent support system for the analysis of power system transients Ibrahim, Awad Ibraik

Abstract

Electromagnetic transients programs such as EMTP are extensively used for simulating fast transient effects in electric power systems. However, these programs are not easy to use for the following two reasons: 1. All of them require a high level of technical expertise to apply them properly. 2. Most of them are not user friendly. This project proposes an intelligent system to support simulations with EMTP and similar programs. The work is composed of three parts; the first part presents the development of a prototype intelligent support system, the second part introduces the knowledge base for switching surge studies, and the third part describes the development of a new line model for the representation of short transmission lines and cables. The intelligent support system is composed of three stages. First, the support system selects a base case from a case database, to be modified to meet the user's requirement. Second, the expert system checks the syntax and validity of the new case data. Finally, the EMTP solution is checked to see whether the chosen models are appropriate for the frequencies contained in the solution, for the degree of imbalance, and for other criteria. If they are not appropriate, better models will be recommended to the user. The knowledge base for switching surge studies solves the problem of selecting the proper models for representing power system components in the EMTP. It helps in checking the validity of the data used to represent the simulated transient phenomena, and gives some suggestions to the user to correct his case data before simulation. It also helps in the evaluation of the results, using the knowledge of the phenomena being simulated. From this knowledge base, the idea of developing a new line model for short lines and cables evolved as one of the practical rules that is recommended for the proposed intelligent support system. The new EMTP transmission line model for the representation of short overhead lines and cables will overcome the limitation of using a time step size not larger than the travel time. The error analysis for the short and open-circuit responses shows that the new line model has a filtering effect for higher frequencies. In a comparison with actual field test measurements, it is shown that the new line model is suitable for a reasonable representation of short overhead transmission lines and cables.

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