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Doğru ışınım tahmini, fotovoltaik (PV) santralinin verimliliğini arttırarak şebekenin etkin bir şekilde programlanmasına ve güç kalitesinin iyileştirilmesine olanak sağlar. Bu çalışma, güneş enerjisi bakımından verimli bir yer olan Hakkâri ilinde kurulan bir meteoroloji ölçüm istasyonu verileri aracılığıyla küresel güneş ışınım tahmininde yapay sinir ağları (YSA) parametrelerinin potansiyelini göstermektedir. Meteoroloji istasyonundan zaman serisine bağlı olarak ölçülen, rüzgâr hızı, sıcaklık, basınç ve nem parametreleri kullanılarak eş zamanlı gerçekleşen güneş ışınım değerleri YSA modeli oluşturularak tahmin edilmiştir. Oluşturulan model YSA’da yaygın olarak kullanılan çeşitli eğitim algoritmaları ve aktivasyon fonksiyonları ile denenmiş ve en iyi sonuç elde edilmeye çalışılmıştır. Kullanılan modelin performansı istatistiksel göstergeler kullanılarak değerlendirilmiştir. Kullanılan veri seti parametrelerine göre güneş ışınım tahmininde, “trainlm” eğitim algoritması ile “poslin” aktivasyon fonksiyonu kullanılarak oluşturulan model 0,97 regresyon değeri, %1,16 ortalama kare hatası (MSE) ve %0,0881 normalize kök ortalama kare hatası (nRMSE) değeri ile güneş ışınım tahmininde en iyi performansı göstermiştir.

Yüksek gerilim iletkenleri, enerji talebinde göz önünde bulundurulması gereken en önemli unsurlardandır. Günümüzde elektrik enerjisine karşı artan talep, güç sistemlerinde kayıp artışı, hat kapasitelerinin yetersizliği, sehim vb. sorunları meydana getirmektedir. Bu sorunları çözmenin birkaç yolu bulunmaktadır. Çözümlerden biri ise, günümüzde kullanılan konvansiyonel iletkenleri, Yüksek Sıcaklık Düşük Sehimli (HTLS) iletkenlerle değiştirerek, iletkenlerde sarkma (sehim) miktarını minimuma indirmek ve daha yüksek sıcaklıklarda çalışabilen HTLS iletkenler üzerinden daha fazla akım iletimi sağlanarak, mevcut durumdan daha fazla akım taşıma kapasitesi elde etmeyi amaçlamaktadır. Fakat bu işlemi yapmadan önce bir de bunun maliyet tarafı ele alınmalıdır. Bu çalışmada, konvansiyonel iletkenler ile HTLS iletkenler teknik ve ekonomik açıdan incelenmiştir. Elde edilen sonuçlara baktığımızda da HTLS iletkenlerin teknik ve maliyet açısından birçok konuda konvansiyonel iletkenlere göre daha avantajlı olduğu görülmüştür.

The development of light sources that provides lighting with electrical energy has a history of about 200 years and it has still been continuing today. Over the time, different light sources have been developed by the use of different technologies. Eventually, a large product inventory comprised from light sources in different structures and characteristics has been obtained. Residential lighting is an important field in the sector in terms of appealing large number of users and a wide range of application areas. In addition, lighting quality is prioritized in residential buildings, because people get more closely exposed to artificial light in those places. In this study, the most commonly used eight different light sources in residential buildings have been investigated. The selected light sources are comprised of the products from halogen, CFL and LED lighting technologies. All the light sources have been chosen with equivalent luminous flux values. The selected light sources have been subjected to photometric and electrical measurements realized simultaneously under the same ambient conditions. The interactions between photometric parameters and the meaning of these magnitudes in terms of users have been tried to be explained in an explanatory language. For the same purpose, electrical parameters have been also examined and their meanings terms of both the user and system have been given. Based on the results obtained, evaluation of the light sources selected from different technologies have been provided sophisticatedly and their suitability in terms of users and systems have been discussed. In the last part, the loading efficacy value has been examined and reference has been made to the appropriateness of the use of this value in expressing the efficiency of the light sources.

For the last few years, there has been a decrease in electricity consumption for lighting purposes. The reason for this decrease is the widespread use of energy saving lighting elements that have high efficacy factor. LEDs are one of these lighting elements and have a very important role on energy saving lighting. On the other hand, power quality problems have started to be experienced more frequently and seriously, so it has become an important issue nowadays. Light emitting diodes are a closely related in both subjects. In this study, the harmonic behavior of RGB WLEDs, which has gained importance recently and has become increasingly widespread, has been investigated. RGB WLEDs, which are quite different from monochrome LEDs in terms of package contents and driver circuit, are expected to behave differently in terms of harmonics. In order to observe that, an appropriate test setup has been established and the power quality measurements of an RBG WLED sample have been performed for different operating cases. In the conclusion of the study, the enlightening results about the harmonic behavior of RGB WLEDs were obtained.

Due to the fact that it is a semiconductor based lighting equipment, the LEDs have important effects on the power quality. In the ever-expanding lighting industry, the use of LED equipment is increasing day by day. Therefore, it is very important to analyze and interpret the effects of LEDs on the grid. In this study, power quality measurements of 4 different commercial LED luminaires have been realized and the results obtained have been interpreted. According to the measurements, it is found that the power factor values are acceptable for the luminaries when they are completely on. However, when the luminaries are dimmed, it has been observed that the power factor decreased and the current harmonics exceeded the limit values determined by the related standards. On the other hand, it is seen that all the luminaires provide flicker boundaries. As a result of the study, it has been concluded that the effects of dimmable equipment on power quality should be analyzed in more detail.

Significant developments on semiconductor technology have captured the electronic industry and paved the way for dominating household appliances market. Typical loads in this market generally have nonlinear voltage-current characteristics. Therefore, highly-integrated power-electronic based electrical equipment in the demand side has caused harmonic pollution, which is one of the most important power quality problems in distribution system operation. To address this issue, there have been significantly great attempts to keep total harmonic distortion (THD) and total demand distortion (TDD) levels within International standard limits defined by IEEE 519 and IEC 61000. On the other hand, load shifting has recently drawn special attention of power grid planners to improve system performance substantially in the smart grid paradigm. In this study, the real harmonic measurements of residential appliances (both linear and nonlinear) are carried out in the Smart Home Laboratory in Yildiz Technical University, Istanbul, Turkey. Different load profiles are then created with a high accuracy based on the measured voltage and current, active, reactive and apparent power. Also, three case studies are considered to investigate the impacts of load shifting strategies on power quality requirements in terms of satisfying the relevant standards. As a result, it is shown that the TDD value decreases below nearly 8% limitation by mitigating the harmonic distortion and the TDD index, which indicates the harmonic distortion effect on the system regarding the desired standard limits of IEEE.

The electromechanical overcurrent protection relays are designed to operate with sinusoidal current. The operation of protective relay with harmonic currents is not reliable. The literature on harmonics and relays covers mostly the theoretical studies. In this paper, the harmonic effects on operation of electromechanical inverse time overcurrent relay ITOCR were examined. Not common in existing studies, the behaviour of ITOCR was analysed with laboratory experiments for distorted waveforms. A type of induction disc relay was used as an electromechanical ITOCR in the experiments. The non-sinusoidal load currents that consist of different harmonic spectra were applied to ITOCR and these nonlinear-load currents were processed by a data acquisition card and a harmonic analysis programme in the computer environment. According to the experiment results, the pick up current and the operating time of the ITOCR increase proportionally to the total harmonic distortion THD value of the non-sinusoidal current. It is concluded that, this type of relay cannot protect the system reliably due to the harmonic components of current., Elektromekanik a ırı akım koruma röleleri sinüsoidal akım altında çalı mak üzere tasarlanmı tır. Bu rölelerin harmonikli akımda çalı maları güvenilir de ildir. Literatürde harmonikler ve rölelerle ilgili pek çok teorik çalı ma bulunmaktadır. Bu makalede, harmoniklerin elektromekanik ters zamanlı a ırı akım rölesinin TZAAR çalı masına etkileri incelenmi ve TZAAR’nin bozulmu dalga ekilleri için davranı ı deneysel çalı ma ile analiz edilmi tir. Deneyde, elektromekanik TZAAR olarak, indüksiyon disk yapısında bir röle kullanılmı tır. De i ik harmonik spektrumlara sahip, sinüsoidal olmayan yük akımları TZAAR’a uygulanmı ve bu yük akımları data toplama kartı ve harmonik analiz programı ile bilgisayar ortamında i lenmi tir. Deney sonuçları gözönüne alındı ında, TZAAR’ın çalı ma akımı ve çalı ma zamanının, sinüsoidal olmayan akımın toplam harmonik distorsiyonu THD ile orantılı olarak arttı ı görülmü tür. Bu yapıda olan bir rolenin, akımın harmonik içermesi durumunda sistemi güvenli bir ekilde koruyamayaca ı sonucu elde edilmiştir

In recent years, sustainable and clean renewable energy resources are widely used instead of fossil fuel energy resources in electrical energy generation systems. Especially, wind and solar energy conversion systems are utilized together in stand-alone systems. In this study, reliability analysis of a hybrid system installed in Davutpasa Campus of Yildiz Technical University is investigated. The system includes a wind turbine, PV panels, a hybrid charge regulator, a MPPT charge controller, an inverter, battery group and loads. Reliability indexes are calculated for analyzed system. The obtained results are examined and presented in this paper.

Energy has always been an important factor for socio-economic development of humans. Most of the energy is generated from fossil fuels in the world. Nevertheless, environmental aspects and depleting of fossil fuels causes increase of renewable energy utilization. The produced energy from renewable energy resources are transferred to grid or used in stand-alone systems. As energy generation depends on environmental conditions, efficiency and energy potential of renewable energy systems changes according to region of installation. In this study, introduction of the solar-wind-battery hybrid system constructed in Davutpasa Campus, Yildiz Technical University, and future work for the system are presented.

Especially with the developing semi-conductor technology, harmonics have become one of the most popular issues in power system. In this study, the measurements for the harmonic effects of the loads in power system were carried out and also contribution of these loads to harmonic distortion was exhibited. Moreover, the effect of harmonics existing in power sys‐ tem on the performance of some equipment was analyzed experimentally. The obtained re‐ sults were discussed and suggestions were given.

Harmonic distortion and flicker severity have become the main concerns in power transmission networks. Different types of harmonic and flicker sources exist in power systems, such as arc furnaces and cycloconverters. A power quality problem found in networks can cause additional temperature rise, losses, noise, and irritation in the lighting equipment. The aim of this study is to identify the level of harmonics and flicker in the 380-kV transmission network of Turkey. The measurement and analysis are performed using a specially developed power quality analyzer. The effects of harmonics and flicker on the network are discussed based on real measurement results. Moreover, the measurement results are compared to the current regulations in Turkey.

This paper presents measurement system and detailed analysis of power quality at the substation of two different wind farm sites which are of low and high power rate. Measurement system has been designed using a data acquisition board (DAQ), Labview software, Matlab programming and a portable PC. The system has been installed at medium voltage level at substation of both wind farms. The real measurement results at substations are compared to current regulations in Turkey. (C) 2009 Elsevier Ltd. All rights reserved.