04_experrt_dielectrc - IEEE TRANSACTIONS ON POWER DELIVERY VOL 19 NO 3 JULY 2004 1127 Investigation of an Expert System for the Condition

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IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 19, NO. 3, JULY 2004 1127 Investigation of an Expert System for the Condition Assessment of Transformer Insulation Based on Dielectric Response Measurements Tapan K. Saha , Senior Member, IEEE, and Prithwiraj Purkait , Member, IEEE Abstract— The need for economic, reliable, and effective delivery of electric power has lead to the search for fast, efficient, and ef- fective methods for diagnosing the insulation of high-voltage (HV) equipment in the power industries. The recent dielectric techniques that have been carefully considered by major industries for trans- former insulation condition assessment are the recovery voltage method (RVM) and the polarization and depolarization current (PDC) measurement. However, due to the complexity of the trans- former insulation structure and various degradation mechanisms under multiple stresses, insulation condition assessment is usually performed by experts with special knowledge and experience. In this paper, an expert system (ES) is developed, which imitates the performance of a human expert, to make the complicated insu- lation condition assessment procedure accessible to plant mainte- nance engineers. The structure of the ES is described in detail in- cluding knowledge base, inference engine, and human–computer interface. Examples of the application of the ES are also presented to confirm that the system can provide accurate insulation diag- nosis. Index Terms— Conductivity, depolarization current, dielectric diagnosis, expert system, knowledge base, oil moisture, paper moisture, polarization current, recovery voltage, transformer aging. I. INTRODUCTION T RANSFORMER is one of the most important and costly apparatus in a power system. The reliable and efficient fault-free operation of the high-voltage transformer has a de- cisive role in the availability of electricity supply. The trans- former oil/paper insulation gets degraded under a combination of thermal, electrical, chemical, mechanical, and environmental stresses during its operation [1], [2]. In recent years, there has been growing interest in the condition assessment of transformer insulation. This is primarily due to the increasingly aged popu- lation of transformers in the utilities around the world. With the growing complexity of power systems, minimization of inter- ruption to customers and reliability of service is of paramount importance. Therefore, assessment of the insulation condition of the transformer is of great industrial interest. Utility engineers use a number of modern chemical diag- nostic techniques to assess the insulation condition of aged transformers. These include dissolved gas analysis (DGA), degree of polymerization (DP) measurement, and furan anal- Manuscript received March 7, 2003. The authors are with the School of Information Technology and Electrical
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This note was uploaded on 06/11/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

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04_experrt_dielectrc - IEEE TRANSACTIONS ON POWER DELIVERY VOL 19 NO 3 JULY 2004 1127 Investigation of an Expert System for the Condition

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