IJE TRANSACTIONS A: Basics Vol. 32, No. 1 (January 2019) 84-89    Article in Press

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Ali Ebadi, S. M. Hosseini and A. A. Abdoos
( Received: August 20, 2018 – Accepted: December 26, 2018 )

Abstract    The restricted earth fault (REF) relay is a type of differential protection which is used for detection of internal ground faults of power transformers. But, during external faults and transformer energization conditions, the probability of current transformer (CT) saturation increases. Thus, the spurious differential current due to CT saturation, can lead to REF relay maloperation. In this paper, a new intelligent REF protection scheme is presented based on the pattern recognition method. In the proposed method, one-cycle data window of differential and neutral currents are used as exemplar patterns of the classifier. The performance of the proposed method is evaluated by obtained data from simulation of a real 230/63 kV power transformer in PSCAD/EMTDC environment. Moreover, in order to accurately simulate the CT behavior during saturation the well-known Jiles-Atherton (JA) model is utilized. The promising obtained results show that the proposed intelligent method increases the security of the REF relay.


Keywords    Power Transformer Protection, Restricted Earth Fault, CT Saturation, Inrush Current, Artificial Intelligence


چکیده    رله خطای زمین محدود شده نوعی حفاظت دیفرانسیل است که برای آشکارسازی خطاهای داخلی زمین ترانسفورماتوور قدرت بکار می­رود. اما طی شرایط خطای خارجی یا برقدار شدن ترانسفورماتور قدرت احتمال اشباع ترانسفورماتورهای جریان بالا می­رود. بنابراین، جریان دیفرانسیلی ظاهر شده در چنین شرایطی ممکن است موجب عملکرد نابجای این طرح حفاظتی گردد. در مقاله حاضر، یک طرح حفاظت خطای زمین محدود شده جدید هوشمند بر پایه روش تشخیص الگو ارائه می­گردد. در طرح پیشنهادی یک سیکل از مقادیر جریان­های دیفرانسیلی و نول بعنوان الگوهای نمونه طبقه­بندی کننده هوشمند بکار گرفته می­شود. عملکرد روش ارائه­شده با استفاده از اطلاعات بدست آمده از شبیه­سازی یک ترانسفورماتور قدرت واقعی kV 63/230 در محیط نرم­افزار PSCAD/EMTDC، ارزیابی گردیده­است. بعلاوه، برای شبیه­سازی دقیق رفتار ترانسفورماتورهای جریان حین اشباع مغناطیسی، مدل معتبر جیلز اثرتون بکار رفته است. نتایج پیاده سازی این طرح حفاظتی هوشمند، ایمنی بسیار مناسب آن در مقابل عملکرد کاذب را تایید نموده است.

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