ارائه یک مدار معادل حرارتی برای تحلیل گرمایی ترانسفورماتورهای قدرت با بارهای هارمونیکی
محورهای موضوعی : مهندسی برق و کامپیوترمرتضی میخک بیرانوند 1 , بهروز رضایی علم 2 , مهرداد جعفربلند 3 , ولی‌اله ابراهیمیان 4 , محسن عسگری 5
1 - دانشگاه لرستان
2 - دانشگاه لرستان
3 - دانشگاه صنعتی مالک اشتر
4 - شرکت برق منطقه‌ای باختر
5 - شرکت برق منطقه‌ای باختر
کلید واژه: المان محدودترانسفورماتور قدرت روغنیجریان‌های غیر سینوسیکاهش بارگیریمدار معادل حرارتی,
چکیده مقاله :
بیشترین خرابی‌های ترانسفورماتورهای قدرت ناشی از مشکلات حرارتی می‌باشد که این مشکلات در شرایط کاری غیر نامی مثل تغذیه بارهای هارمونیکی بیشتر بروز پیدا می‌کند. تحلیل گرمایی ترانسفورماتور و گرمای اضافی تحمیل‌شده به ترانسفورماتور به علت وجود هارمونیک‌ها موضوع مورد بررسی این مقاله است. در این مقاله یک مدار معادل حرارتی جدید ارائه می‌شود به نحوی که دمای اجزای مختلف ترانسفورماتورهای قدرت روغنی را به صورت تفکیک‌شده در شرایط تغذیه بارهای هارمونیکی مشخص می‌کند. تلفات اجزای مختلف ترانسفورماتور به عنوان منبع تولید حرارت بایستی محاسبه شوند و به این منظور در این مقاله یک روش مدل‌سازی المان محدود 3بعدی مناسب پیشنهاد شده است که قادر به محاسبه تلفات اجزای مختلف ترانسفورماتور قدرت با ساختار هندسی پیچیده است. مقایسه نتایج به دست آمده از مدار معادل حرارتی پیشنهادشده با دماهای نقاط داغ سیم‌پیچی و میانگین روغن به دست آمده از 57.91IEEE Std C نشان می‌دهد مدار معادل حرارتی پیشنهادی از دقت کافی برای تخمین توزیع دمای ترانسفورماتور تغذیه‌کننده بارهای هارمونیکی برخوردار است. به منظور جلوگیری از افزایش دمای ترانسفورماتور با تغذیه بارهای هارمونیکی، کاهش بارگیری ترانسفورماتور مورد بررسی قرار می‌گیرد.
The majority of the power transformers failures are caused by the thermal stresses under abnormal operating conditions, such as harmonic loads. Therefore, it is of great interest to determine the temperature distribution inside the power transformers. In this paper, a new thermal equivalent circuit is presented by which the temperature in different regions of the transformer is estimated under harmonic loads. Also, the three-dimensional Finite Element (FE) Model of the power transformer is developed to calculate the power losses in each part of the transformer that are considered as the heat sources in the proposed equivalent circuit. The computed hotspot and average oil temperatures are compared with those obtained from IEEE Std C57.91 method, thereby the accuracy of the proposed method for calculating the temperature rise due to harmonic loads, is investigated. Finally, derating of the power transformer is discussed under harmonic loads.
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