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ORAL, BÜLENT

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    Electric field analysis of 66 kV and 110 kV SiR insulators under combined AC-DC voltages
    (2021-09-30) İSPİRLİ, MEHMET MURAT; ORAL, BÜLENT; İSPİRLİ M. M., ORAL B., KALENDERLİ Ö.
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    PublicationOpen Access
    Electric field analysis of 66 kV and 110 kV SiR insulators under combined AC-DC voltages
    (ELSEVIER, 2022-04) ORAL, BÜLENT; Ispirli, Mehmet Murat; Oral, Bulent; Kalenderli, Ozcan
    Insulators are the most crucial part of power systems. The insulation performance of insulators is vital for the sustainability of power systems. Recently, silicone rubber (SiR) insulators are used frequently in all sections of the power systems. In this paper, a SiR insulator currently used in power transmission systems has been analyzed under combined AC-DC voltage using the finite element method. In the analysis, positive and negative DC voltages in different amplitude ratios were superimposed over the phase-earth operating voltage of the insulator. Analyses in the study were made in time-dependent. Only DC voltage was applied to the insulator for the first 60 s, AC + DC voltage was applied between 60 to 120 s. Thus, the electric field behavior of the SiR insulator under combined AC-DC voltage has been obtained. The change of electric field based on positive and negative DC components was investigated. As a result of the study, the effect of the polarity of the DC component in the combined voltage was observed. As a result, effect of the polarity of the DC component in the combined voltage on the maximum electric field intensity was observed. (C) 2021 The Author(s). Published by Elsevier Ltd.
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    PublicationOpen Access
    Investigation of impact of DC component on breakdown characteristics for different electric fields under composite AC & DC voltage
    (WILEY, 2022-01-13) ORAL, BÜLENT; Ispirli, Mehmet Murat; Kalenderli, Ozcan; Seifert, Florian; Rock, Michael; Oral, Bulent
    The valve side of the converter in the high-voltage direct current is subjected to mixed voltages such as composite AC & DC voltage. In this study, the effects of the homogeneity of electric field on breakdown voltage were investigated for different +/- DC component amplitudes of the composite voltage. The field efficiency factor was calculated using mean and maximum field strengths for all of them. Variation of breakdown voltage of air was examined under the composite AC & DC voltage for different ratios +/- DC. As one result of the study, the breakdown occurs at the positive half-wave of the AC voltage despite - DC voltage being applied due to positive corona discharge pulses. This breakdown point is named as the polarity change point. The breakdown voltage increases with the decrease of DC voltage component up to polarity change point in nonuniform electric field. In less uniform electric field, the AC breakdown voltage was measured slightly higher than the DC breakdown voltage. In less uniform electric field, as the ratio of the applied AC voltage to DC voltage increases, the breakdown voltage gradually approaches the AC breakdown voltage. This result is similar to the result obtained for the +DC component in non-uniform electric field experiments.
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    PublicationOpen Access
    Challenges during commissioning and operation in photovoltaic power plants by electrical faults
    (2023-05-01) SAĞLAM, ŞAFAK; ORAL, BÜLENT; Gökgöz M., SAĞLAM Ş., ORAL B.
    Problems such as increasing environmental pollution and global warming due to fossil fuels used in energy production have revealed the requirement for renewable energy sources. In addition to this situation, the decreasing fossil fuel reserves, and the need to diversify energy production resources to ensure energy supply security for countries have made the use of renewable energy sources a necessity. Therefore, demand for solar energy will continue to increase, considering the increasing renewable energy need. To increase energy efficiency, the uninterrupted production of photovoltaic power plants during production hours is important to reduce the consumption of fossil fuels. For this reason, situations and malfunctions that prevent uninterrupted operations should be detected. Fault classification contributes to the rapid identification of problems by providing fast diagnostics for possible faults. When the previous studies in this field are examined, there are publications about general faults in photovoltaic power plants and publications about electrical faults separately. However, there are limitations in academic studies that deal with the difficulties encountered in the commissioning and operation of photovoltaic power plants in detail and examine electrical faults. In this context, there is a need for relevant studies. In this study, the possible failures that may occur during the commissioning and operation of photovoltaic power plants will be categorized and this study is intended to be a resource for studies on this subject. It is aimed to create a resource for academic studies and to contribute to field applications to companies in the sector.
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    Natural gas reserve/production ratio in Russia, Iran, Qatar and Turkmenistan: A political and economic perspective
    (ELSEVIER SCI LTD, 2016) ORAL, BÜLENT; Esen, Vedat; Oral, Bulent
    In this study, changes in natural gas reserve/production ratio (R/P) of the four countries having the highest natural gas reserves (Russia, Iran, Qatar, Turkmenistan), the importance of which increases in the world market each day due to developing technology and the demand for clean energy, has been analyzed depending on the economic and political developments in national and international fields. Change of R/P ratio depending on years has been displayed on graphics from different sources and these alterations have been tried to be associated with such issues as natural gas agreements in history, hand over of political authority, economic crises etc. Therefore; it has been put forward whether or not political and economic changes of the countries are factors on the amount of natural gas production and the discovery of new reserve fields with the addition aim of providing a general overview on natural gas market. (C) 2016 Elsevier Ltd. All rights reserved.
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    PublicationOpen Access
    Application and comparative analysis of fuzzy inference system for transformer fault diagnosis with dissolved gases in oil
    (2021-10-28) ORAL, BÜLENT; İSPİRLİ, MEHMET MURAT; İSPİRLİ M. M., Adalı H., KALENDERLİ Ö., Çelik M. Z., ORAL B.
    Oils are used for cooling and insulation in transformers. The fault currents occurred on transformers can damage windings and insulation. As a result of this incoming fault current, gas emission occurs in materials such as oil and pressboard. The type of these gases released gives information about the fault of the transformer. In this study, it has been studied on the determination of the fault by analyzing the gases released as a result of the failure in 63 transformers using FIS. As a result of the analysis, the results obtained with FIS were compared with analyzed results with IEC 60599 and fault reports from the corporation, which these values obtained. When 63.5% true results were obtained compared to IEC 60599, 97.6% correct results were obtained compared to fault reports of the corporation because 22 of 63 transformer gas values were not actually suitable for applying the IEC Ratio method.
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    PublicationOpen Access
    The importance of in-service training in restructuring sectors
    (ELSEVIER SCIENCE BV, 2010) ORAL, BÜLENT; Oral, Bulent; Saglam, Safak; Uzunboylu, H
    Reduction or abolishment operation of government's intervention to economy, accelerating since the beginning of 1980s, is adopted by many governments as governance policy. This policy, being widely used in manufacturing industry and service sector at the beginning, has been used subsequently in electricity, natural gas, water ... etc industry as natural monopoly. The employee needs to know position at institution organization, individual value and expectations. It is effective on the employee performance. In this context, the employees can take in-service education their institutions and regulatory authorities, which regulate and supervise the sectors. The in-service education plan is supported the program content and process by academic circles. In this study, it is emphasized process and content of scheduled in-service education program.
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    Light sources of solar simulators for photovoltaic devices: A review
    (PERGAMON-ELSEVIER SCIENCE LTD, 2017) ORAL, BÜLENT; Esen, Vedat; Saglam, Safak; Oral, Bulent
    As solar power usage is increasing nowadays, performance tests have become one of the most important topics in order to guarantee the security of photovoltaic tools. For photovoltaic panels to become efficient, there is need for health testing of all materials and technologies used in the production of the panels in electrical and optical aspects. Thus, when future energy standards are considered, it is imperative to use solar simulators that obtain near real sunlight spectrum values. The most important components of solar simulators used in photovoltaic panel tests are light sources. In this study, solar simulators' were classified based on the light sources they use, and their history and technological development were investigated in line with the literature. Within the scope of this study, carbon arc lamps, sodium vapor lamps, argon arc lamps, quartz-tungsten halogen lamps, mercury xenon lamps, xenon arc, xenon flash lamps, metal halide lamps, LED and super continuum laser light sources were investigated. Additionally, to compare spectral deficiency among these light sources and solar simulators, multiple light sourced solar simulators were also covered under a separate title.
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    Enerji teknolojileri (Orta Okul)
    (TÜBİTAK Bilim ve Toplum Başkanlığı, 2023-01-01) SAĞLAM, ŞAFAK; ORAL, BÜLENT; Oral B., Sağlam Ş.
    Enerji; yaşamımızda en çok duyduğumuz ve kullandığımız kavramlardan biri olmakla beraber, günümüzde sosyal, ekonomik, teknolojik ve çevresel yönleriyle ele alınan ve değerlendirilen çok geniş bir kapsama sahiptir. Kavram olarak günlük yaşamda farklı kullanımları ve birçok disiplinde farklı tanımlamaları vardır. Günlük yaşamda kullandığımız enerji kavramı, kullanıma göre farklı büyüklüklerin oluşmasına neden olur. Bu büyüklükleri bilmek ve yaşamımızın içerisinde bilinçli olarak kullanmak, hem topluma hem de bireylere ekonomik ve çevresel faydalar sağlayacağı bir gerçektir. Bu kapsamda toplumun tüm eğitim seviyelerinde okul öncesinden başlayarak, yaşam boyu öğrenme süreci ile enerji okuryazarlığı kavramı ele alınmalı ve geliştirilmelidir. Böylece bireylerin günlük kullanımlarında farklı bakış açıları ve gelişim süreci elde edebilir.Enerji teknolojileri; enerjinin üretiminden tüketimine kadar birçok alt sistem ve bileşeni kapsamaktadır. Çok büyük etki alanına sahip olan enerjinin üretim-tüketim sürecinde sürdürebilir yaşamı desteklemek, ekonomik ve teknolojik olmak gibi birçok ölçüt öne çıkmaktadır. Bu kapsamda enerji teknolojilerinin yenilenmesi, genel olarak mevcut teknolojileri iyileştirmek veya yenilerini oluşturmak olarak ifade edilmektedir. Uzun vadeli olarak enerji teknolojileri üzerine yapılan araştırmalarda ve istihdamda uluslararası literatürdeki çalışmaların kapsamında en önemli üç başlık; enerji verimliliği, enerji depolanması ve yenilenebilir enerji kaynakları olarak ifade edilmektedir. Bu temel alanlar öğrencilerimizin yönlendirilmesi açısından önemlidir.Sunulan bu çalışmayla öğretmenler, enerji teknolojileri başlığı altında öncelikle öğrencilerin enerji kavramından başlayarak, enerji okuryazarlığı ve sürdürülebilir yaşamı destekleme süreçlerini kavramaları hedeflemelidir. Bu çerçevede çalışmada ilk olarak enerji kavramının tanımı, büyüklük olarak anlamı, dönüşümü, enerji verimliliği konuları yer almaktadır. Sonraki aşamada ise, enerji teknolojilerinin üretim süreçleri ele alınmaktadır. Böylece geleneksel ve yenilenebilir enerji kaynakları üzerine enerji teknolojileri ifade edilmektedir. Özellikle çalışmada rüzgâr ve güneş bazlı yenilenebilir enerji üretim teknolojileri detaylı olarak sunulmaktadır. Son olarak, günümüzde enerji teknolojilerinin en önemli parçası haline gelen enerji depolama sistemleri üzerine bir bölüm çalışma içinde bulunmaktadır. Bu çalışma, öğretmenlere \"Dene ve Yap\" öğrenme süreci içerisinde öğrencilerin konuları ele alması yaklaşımıyla oluşturulmuştur. Özellikle deney sürecinde öğrencinin karşılaşacağı sorunlara vereceği çözümler, değişkenlerin belirlemesi ve nasıl değişeceği gibi fikirler, yaparak ve yaşayarak öğrenme sürecini oluşturması bu çalışmanın istenen aşamalarıdır. Enerji teknolojileri başlığı altında verilen bu çalışma diğer Deneyap başlıklarından farklı olarak, konunun içeriği ve farklılığı nedeniyle öğrencilerin en yüksek düzeyde anlama ve kavrama sağlamak hedefi ile 5E öğretim yöntemi kullanılarak tasarlanmıştır. Bu çalışmanın 5E öğrenme döngüsü modeli ile öğrencilerin araştırma sorgulamaya teşvik etmesi hedeflenmektedir.Böylece \"Enerji Teknolojileri\" başlığı altında mühendisliğin temel konularına odaklanılarak, enerji kavramı üzerine açıklama ve tanımlamalar yapılması sağlanacaktır. Analitik bir çerçevede enerji kavramını açık bir şekilde öğretmek, disiplinler arası sorunlar hakkında düşünmesini sağlamak iyi donanımlı yeni nesil bilim insanları ve mühendisler yetiştirmeye yardımcı olacaktır.
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    Smart indoor LED lighting design powered by hybrid renewable energy systems
    (ELSEVIER SCIENCE SA, 2017) ORAL, BÜLENT; Kiyak, Ismail; Oral, Bulent; Topuz, Vedat
    It's important to provide diversity in energy resources and to use sustainable energy resources besides local resources. In the recent years, LEDs have been increasingly used in interior lighting systems because of their low energy consumption, high light-flux efficiency and their ability to maintain the light-flux value at a constant level for a long period of time. In this study, a LED luminaire was designed by using the Osram Coinstar W4 brand power LED module. An LED drive card, which is a specialty of the luminaire, was designed to provide ideal functioning conditions and serve as a power supply for the LEDs. A communication card was designed for all kinds of information exchange between the LED luminaires, motion detectors and light sensors used with the laboratory lighting system, and an RS485 communication line was installed to connect every system. Under the control of the luminaire, the lighting was tested by a fuzzy-expert system. With this project design and test, a system was developed that can be used in interior spaces. (C) 2017 Elsevier B.V. All rights reserved.