توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱A Distribution Transformer Comprehensive Optimal Planning and Sizing Method
اطلاعات انتشار: اولین کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی برق و کامپیوتر، سال
تعداد صفحات: ۷
A significant part of the power system losses are due to the distribution transformers energy losses. The high share of these transformers to the electric energy losses of the country’s power network in each year, contribute to an important share in the loss of national yearly resources and country budget. On the other hand due to the high rate of yearly increase in electric energy usage in the country, optimal distribution transformer planning and sizing has a very important role in saving these losses over the future years. To address these concerns, it is required for the distribution companies to help optimize utilization of electric energy sources, which results in increase of distribution companies’ benefits. This paper introduces a method for proper, optimal and intelligent selection of distribution transformers power rating and efficiency class. This will increase the distribution companies’ benefits through reduction in the respected energy losses. The previously used methods in the country, didn’t model the replacement of a distribution transformer with another one of different rating. This paper models different scenarios, realizing yearly future load growth in a region, besides possibility of stablishing a new substation to develop a comprehensive algorithm for distribution transformer planning and its replacement during its life. Final target of this work is the development of a code for optimized planning of a new distribution substation. The proposed algorithm prepared for Tehran’s Large Electricity Distribution Company and demonstrated promising results.<\div>

۲High Impedance Restricted Earth Fault Protection: Fundamental Concepts, Design and Performance
نویسنده(ها): ، ،
اطلاعات انتشار: کنفرانس بین المللی مهندسی برق، سال
تعداد صفحات: ۶
Power transformers are a critical and expensive component of the power system. The comprehensive transformer protection provided by combination of protection elements, with biased differential protection. Differential protection has excellent operation in most fault cases, but in the situations that a single phase to ground fault occurs near the neutral point in solidly grounded transformers, the faulted phase current increases slightly and causes differential protection not to detect the fault. For this reason, restricted earth fault (REF) relay can be used as a complementary of differential protection. REF protection uses the sufficient current that flows in this condition through the neutral conductor, for relay operation under phase to ground fault. The REF protection scheme is composed of two parts: a high impedance REF unit and a low impedance REF unit. The high impedance REF relay is defined as a relay circuit whose voltage setting is not less than its calculated maximum terminal voltage which corresponds to the maximum through fault current under transient condition. This REF protection scheme provides a high speed and absolutely stable means of protection when ground fault occurs near the windings neutral point in a solidly grounded transformer. This paper summarizes the operating principle of a high impedance protection unit, its relay sensitivity, related CT requirements, importance of a reliable protection, and the necessary setting consideration to be incorporated besides a transformer differential relay<\div>
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