S. A. Hosseini ¹, F. Razavi ², M. Karami ¹, A. A. Ghadimi ³, S. S. Karimi Madahi ¹

Affiliations
1 Department of Electrical Engineering, Islamic Azad University, Ashtian Branch, Ashtian, IR
2 Department of Electrical Engineering, University of Tafresh, Tafresh, IR
3 Department of Electrical Engineering, Science and research branch, Islamic Azad University, Arak, IR

Abstract

SiC lightning arresters are a kind of lightning arresters that nowadays are substituted with new type such as ZnO lightning arrester. Nonetheless, many SiC lightning arresters in Iran's electricity networks are operating. For instance, all the medium voltage network lightning arresters of Bakhtar Regional Electrical Company (BREC) are SiC type. The company wants to exchange these lightning arresters, but due to high cost and numbers of these lightning arresters, it is decided to put them in suitable ranks up to a due time. Since all suggested tests for recognition of lightning arresters deficiency are laboratory tests and must be done in lab, it isn't possible for the company to transfer all lightning arresters from substation to lab. Therefore, it has been decided to carry out that in the substation. Accordingly, a project has been suggested and carried out by the writers of this paper and the present paper is the result of this project. Different theories in this paper are surveyed. DC test is introduced as a suitable way for correct recognition deficiency of lightning arresters. The acquired results of DC test on some samples of lightning arresters are in coordination with the standard tests that have been carried out in Pars High Voltage Lab. Finally, three groups of arresters are defined according to their operating condition which includes acting good, delayed acting and not operating arresters. According to this classification, BREC is capable to exchange the arresters with respect to condition of the related arrester and with an appropriate priority which is obtained from its condition.

Keywords

SiC Lightning Arrester, Electricity Network

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A. Baniassadi ¹, A. H. D. Markazi ¹, M. Karami ¹

Affiliations
1 Department of Mechanical Engineering, Iran University of Science and Technology

Abstract

The idea of robust control is employed to utilize a simpler Weiner model of a gas turbine instead of more complicated thermo dynamical models. Two sources of uncertainties are considered: (1) uncertainties due to nonlinear look-up tables in the Weiner model, which are obtained from experiments on the real engine, and (2) un-modeled dynamics which cannot be captured by the simple structure of the Wiener model. For simplicity, instead of the real engine experiments, a thermo dynamical non-linear model of the engine is considered. The frequency domain behavior of the Wiener model is compared with the nonlinear model and the observed deviations are considered as unknown uncertainties. Two robust controllers, using the well-known D-K iteration methods, are designed for the Wiener model under the presence of such uncertainties, which is then applied on the nonlinear model. Finally, for further investigations and introduction of more uncertainties, a real-time engine simulator is developed, which serves as a more uncertain system due to computational and communication time delays. Study of various time responses resulted by applying a set of step inputs with different magnitudes show that by design of a robust controller for simple Weiner's model of gas turbine, a better performance and robustness will be achieved in comparison with PID control methods. Besides, modeling and controller design have very simple structure in this method in contrast with complicated non-linear methods.

Keywords

Gas Turbine, Weiner Model, Robust Control, Uncertainty, Modelica, Real Time Simulation

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