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Öğe An Assessment on Aging Model of IEEE/IEC Standards for Natural and Mineral Oil-Immersed Transformer(Ieee, 2011) Biçen, Yunus; Çilliyüz, Yusuf; Aras, Faruk; Ayduğan, GüzideThis paper presents an assessment on aging model of IEEE and IEC standards using thermal model of oil-immersed power transformer for natural ester and mineral oil. For this purpose, a model created for the analysis of behavior transient thermal performance with aging both of natural ester and mineral oils. Thermal model of the transformer is based on thermal-electrical analogy that is calculated separately for natural and mineral oils covering top-oil and hot-spot temperatures. The hot-spot temperature values of each ester/oil are used to calculate aging parameters which include the aging acceleration factor, time dependent relative aging rate and insulation life loss variations.Öğe Fuzzy logic-based user interface design for risk assessment considering human factor: A case study for high-voltage cell(Elsevier, 2014) Aras, Faruk; Karakaş, Ercüment; Biçen, YunusThis paper presents a novel risk assessment model considering human factor based on the fuzzy logic approach. For the contribution of the literature, not only the number of people is included in the process of risk assessment, but also with the human factor as a quantitative entry in this study. A flexible and user-friendly risk assessment interface is developed using LabVIEW program, which puts at disposal different applications for the course material. Designed interface gives an opportunity to users to assess risks in a wide range of consequences containing many different combinations and options. The interface is tested for a 100-kV high-voltage cell as a case study. As a result, it is seen that the interface assesses plenty of input elements and possibilities in a short time. For this reason, the fuzzy logic approach is suggested as a suitable method for risk assessment. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Intelligent Condition Monitoring Platform Combined with Multi-agent Approach for Complex Systems(Ieee, 2014) Biçen, Yunus; Aras, FarukCondition monitoring and data analysis are key factors to avoid unexpected catastrophic breakdowns and detect incipient failures. Managing of these processes are not easy in complex system which has many inputs/outputs and interdependent relationships. In conventional methods, the condition monitoring is carried out separately and systematically due to the large number of monitoring point. This paper presents an intelligent condition monitoring platform (ICMP). This platform uses multi-agent system (MAS) advantages via mathematical process named failure sensitive matrix (FSM). Through this platform, the whole system is dynamically monitored, despite all the complexity. Cause and effect relations of a fault are evaluated more comprehensively and the success of achieving global results is higher. The growth of monitoring equipment or system is not a problem, because matrix structure is expandable as wanted and its performance is fast due to the nature of the parallel computation. Other important advantage of this platform is that it is an interface which works with expert systems and artificial intelligence techniques with no restrictions.Öğe Lifetime Estimation and Monitoring of Power Transformer Considering Annual Load Factors(Ieee-Inst Electrical Electronics Engineers Inc, 2014) Biçen, Yunus; Aras, Faruk; Kırkıcı, HülyaThis paper focuses on the realistic remaining service life prediction and monitoring system of power transformers, using an algorithm developed by the authors. The power transformer is one of the vital components of power transmission and distribution substations. It is important to know the loading capacity and remaining service life of a power transformer to ensure its economical and secure operation. This information is directly related to the condition of cellulosic insulation. According to classical method of prediction, the power transformer is considered to be operated under constant load for the remainder of its lifespan. However, in reality the load factor varies continuously, and this is a key factor affecting the service life of power transformers. In this study, a realistic method for monitoring and predicting the service lifetime of power transformers is presented by considering annual load factors. The proposed method is applicable to any power transformer and can be updated by considering relevant standards for different liquid and solid insulation materials. As a case study, life-loss calculation and the remaining service life predictions are carried out using a thermal model that has been created considering a 250 MVA mineral oil-immersed power transformer.Öğe Loadability of power transformer under regional climate conditions: the case of Turkey(Springer, 2014) Biçen, Yunus; Aras, FarukThis paper presents an accurate methodology and examines the effects of long-term ambient temperature changes on the power transformer loadability and its service life loss considering regional climate characteristics. The daily ambient temperature variation is modeled on yearly basis for different climate regions according to historical records. For this purpose, four different regions are selected in Turkey. Thermal and service life loss models are tested under two loading conditions for selected climate projections. Models used in the study, are created in accordance with IEEE C57.91-95 and IEC 60076-7 standards. Calculations are made in high resolution as the basis of second distinct from related standards, for mineral oil-immersed power transformer parameters. In this way, the impact of regional climate conditions on power transformer loadability is determined more accurately. The results show that the power transformer loadability is a function of the regional climate conditions. In addition, the result of the analysis, some coefficients are recommended for power transformer loadability to complete a normal service life range (20.55 years) under selected regional climate conditions. This methodology is applicable to the different climate regions and power transformers outside scope of this study.Öğe Measurements and performance evaluations of natural ester and mineral oil-immersed identical transformers(Elsevier Sci Ltd, 2021) Cilliyuz, Yusuf; Bicen, Yunus; Aras, Faruk; Aydugan, GuzideThe use of natural esters as an insulating liquid has become popular since the early 2000s. Studies in the literature emphasize the superiority of natural esters as compared to mineral oils. In these studies, the prominent properties of natural esters are presented as being environmentally friendly, safe, and delaying the aging of cellulosic insulation material. Although there is no doubt in terms of their characteristics, such as being environmentally and safe, exaggerated comments are made about the delay of aging of the paper material used in the insulation of transformer windings. This is because comparative experimental applications on mineral oil and natural esters are carried out under artificial and equal conditions provided in the laboratory environment. Whereas, performing these experiments on identical transformers will give more realistic results. In this study, two identical transformers were designed and equipped with precision fiber optic temperature sensors. Temperature differences that vary depending on the load between high voltage and low voltage windings were measured with a high degree of accuracy for both identical transformers. Besides these measurements, physical and chemical changes were analyzed on samples taken from insulation liquids. It was observed that the physical and chemical properties of the insulation liquids directly affect the operating performance of the transformers. Thanks to the differences in viscosity of insulating liquids, the heat dissipation due to losses in the windings were different for both transformers. Both heat distribution and temperature differences in the windings varied depending on the loading factors. Considering all these factors together, comprehensively evaluations were made on the aging rate of cellulosic insulation and the service life of the transformers.Öğe A Novel Gui Simulation Program Designed for Teaching of Underground Power Cables(Ieee Computer Soc, 2009) Biçen, Yunus; Aras, FarukThis paper presents a novel computer simulation program designed to aid teaching process in course of underground power cables for engineering students. The calculation of power cable ratings uses several different formulas and long analytical processes based on JEC 60287 and IEC 60853 standards. Therefore it is difficult to examine different variations such as power cable properties, installations and operation conditions, during the restrictive lesson time. For these reasons, a program has been developed to use for teaching process of the power cable course. The program allows the users to effectively learn the rating of underground power cables under different operation conditions with illustrative figures. The program details are presented and explained in this paper.Öğe A realistic method for remaining service life prediction of power transformer(Praise Worthy Prize S.r.l, 2013) Biçen, Yunus; Aras, Faruk; İsmailoğlu, HasbiIn recent years, many studies have been done on monitoring, analyzing and aging performance of power transformer which is one of the most important components of power system. It is important to know the loading capacitance and remaining service life of a transformer to ensure its economical and secured operation. In this study, a realistic method is presented for remaining service life prediction and life-loss calculation of the power transformers. The proposed method is applicable for all the power transformers and can be updated in the light of the relevant standards for the different liquid and solid insulation materials. As a case study, life-loss calculation and the remaining service life prediction is carried out using thermal model that has been created considering the parameters of the 250 MVA mineral oil-immersed power transformer. © 2013 Praise Worthy Prize S.r.l. - All rights reserved.Öğe A robust algorithm based on a failure-sensitive matrix for fault diagnosis of power systems: an application on power transformers(Tubitak Scientific & Technical Research Council Turkey, 2015) Biçen, Yunus; Aras, FarukIn this paper, a robust algorithm for fault diagnosis of power system equipment based on a failure-sensitive matrix (FSM) is presented. The FSM is a dynamic matrix structure updated by multiple measurements (online) and test results (offline) on the systems. The algorithm uses many different artificial intelligence and expert system methods for adaptively detecting the location of faults, emerging failures, and causes of failures. In this algorithm, all data obtained from the power transformer, which have various nonlinear input and output parameters, are processed using the parallel matrix structure of the FSM to reach a global solution quickly. The parameters of a power transformer are used to verify the algorithm under 4 operating conditions simulated in the MATLAB-Simulink program. The obtained results show that the algorithm is convenient for determining incipient failures of a system that consists of multiple parameters.Öğe Smart asset management system for power transformers coupled with online and offline monitoring technologies(Pergamon-Elsevier Science Ltd, 2023) Bicen, Yunus; Aras, FarukPredictive maintenance strategies have gained popularity in recent years due to the advantages they provide over traditional maintenance strategies. Online monitoring technologies are critical for implementing predictive maintenance strategies. However, in some cases, the information generated by online systems may not be accurate and may need to be verified with offline monitoring technologies. In this study, a fault-sensitive matrix-based smart asset management system that is compatible with both online and offline technologies has been developed for power transformers. The developed system has the ability to assess multi-input parameters simultaneously and holistically. Because of the system's matrix structure, having a large number of input parameters or expanding them later is not an issue. Furthermore, the algorithms that will evaluate the input parameters are independent and distinct from one another. Because of its compatibility with the data acquisition card and its design options for the user interface, LabVIEW has been chosen for the system's development. The functionality of the system has been tested by deliberately generating faults in a test cell. While the high-resolution sensor data obtained and the calculated results are displayed on the interface, the failure probabilities are evaluated and displayed in a separate window. Intentionally generated faults have been diagnosed with high accuracy after going through the online monitoring and offline verification processes.Öğe Steady State Effects of Design Properties and Environmental Conditions on Underground Power Cable Ampacity(Ieee, 2017) Biçen, Yunus; Aras, FarukThe steady state analysis of the cables under selected design and installation conditions provide information to ensure that the cables remain within allowable operating temperature limits. Manufacturers share the ampacity levels and derating factors under certain conditions for the cables that they produced, depending on the standards. However, the diversity of conditions can increase in the real applications. In this study, ampacity comparisons have been carried out for a different design and environmental characteristics of an underground cable system. The selected parameters have been analyzed for steady-state conditions within certain ranges. Characteristic ampacity trend curves corresponding to the relevant parameter changes have been generated with iterative solutions.Öğe Thermal modelling and analysis of high-voltage insulated power cables under transient loads(Wiley, 2013) Aras, Faruk; Biçen, YunusThis article presents a simple thermal model for transient analysis of high-voltage underground power cables based on proper ladder diagram at MATLAB-Simulink software under various operating conditions for engineering students. Available commercial programs created with commercial worries are not suitable for students during the learning process, which involve different applications on power cable analysis. The model gives an opportunity for students to solve the often-faced transient problems in utilities. The transient model of the underground power cable system using the analytic procedures based on IEC60853 standards is presented with an example solution of the 154kV power cable in service in Turkish transmission system in this article. (c) 2010 Wiley Periodicals, Inc. Comput Appl Eng Educ 21: 516-529, 2013
