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Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2015, Thesis (M.Sc.) -- İstanbul Technical University, Instıtute of Science and Technology, 2015, Yenilenebilir enerji kaynaklarının daha verimli ve daha erişilebilir hale gelmesiyle birlikte birçok birey veya kurum kendi elektrik enerjilerini üretmeye başlamıştır. Ayrıca, merkezden uzak küçük yerleşim birimlerine yüksek güçlü merkezi santrallerde üretilen elektrik enerjisini iletmek masraflı bir işlemdir. Bu temel sebepler mikroşebeke kavramının ortaya çıkmasını sağlamışlardır. Mikroşebekelerin amacı aynı şehir şebeke sistemlerinde olduğu gibi elektrik üretmek ve üretilen elektriği civardaki yüklere iletmektir. Ancak, mikroşebekeler boyutları bakımından daha küçüktür, ayrıca bir çok dağıtık üretim kaynağı içermektedirler. Bu dağıtık üretim kaynakları güneş panelleri, rüzgar türbinleri, biyogaz tesisleri, çeşitli enerji depolama üniteleri gibi genellikle düşük güçlü kaynaklar olmaktadır. Mikroşebekeler sadece mikro generatör olarak adlandırılan bu düşük güçlü dağıtık üretim kaynakları ve çeşitli yükler ile işletilebilirler veya bir ana şebekeye bağlı olarak çalışabilirler. Şebekeye bağlı çalışma durumunda mikroşebekede üretilen fazla enerjiyi ana şebekeye aktarırlar, eğer yerel kaynaklarda üretilen enerji bölgedeki yükler için yetersiz kalıyorsa ana şebekeden enerji alırlar. Herhangi bir arıza durumunda veya istemli olarak, mikroşebekenin ana şebekeyle olan bağlantısı kesilebilir, böylece mikroşebeke güç adası modunda çalışmaya başlar. Mikroşebekeler gerekli koruma ve kontrol sistemlerine sahiplerse ada durumunda çalışmaları bir sorun teşkil etmez aksi halde sistem düzgün şekilde çalışmayacak, frekans ve gerilimde büyük değişimler meydana gelecektir. Mikroşebekeler genellikle birden fazla kaynak içerdikleri, yenilebilir enerji kaynakları gibi oldukça değişken güç üreten kaynaklar barındırdıkları, şebekeye bağlı ve güç adası modunda olmak üzere farklı çalışma durumlarına sahip oldukları için güç akışı da buna bağlı olarak büyük değişimler gösterebilmektedir. Bu sebeple mikroşebekelerin kontrolü ve koruması radyal yapıya sahip geleneksel şebekelere nazaran daha zordur. Günümüzde sıklıkla karşılaştığımız geleneksel yönlü aşırı akım koruması birçok büyük sistemi başarıyla korumak için yeterli olabilmektedir. Bu koruma sisteminde kullanılan röleler akımın genliğine bakarak arızayı tespit eder, akımın yön bilgisi de arızanın koruma bölgesinde olup olmadığını tespit etmesine yardımcı olur. Eğer örnek sistemde olduğu gibi ters zamanlı röleler kullanılırsa rölelerin zaman gecikmeleri de akımın genliğine bağlı olarak değişecek şekilde ayarlanabilir. Bu tip rölelerin koordinasyonu için ardışık röleler arasında zaman aralıkları kullanılır. Rölenin arızayı algılama alt sınırının belirlenmesi ve zaman aralıklarının uygulanması için rölenin ayar değerleri olan IS ve TMS uygun şekilde ayarlanır. Birbirleri arasında veya merkezi bir kontrol ünitesiyle haberleşme hattına sahip olmayan bu rölelerin ayarlarının bir kez ayarlandıktan sonra tekrar değişmesi sadece manuel olarak mümkündür, bu işlem otomatik olarak gerçekleşemez. Bu sebeple bu koruma şeklinin, şebekedeki yük akışının sıklıkla değiştiği durumlarda kullanılması oldukça güçtür. Yük akımının sıklıkla değiştiği durumlar için bu değişimlere uyum sağlayabilen bir koruma sisteminin kullanılması gerekmektedir. Bu koruma sistemi de adaptif koruma sistemi olarak adlandırılır. Adaptif koruma şebedeki akım bilgilerini ve kesicilerin durumlarını kontrol eder, değişiklik tespit edilmesi durumunda yük akışını tekrar hesaplar ve röle ayarlarını buna bağlı olarak değiştirir. Adaptif koruma sisteminin uygulanması için rölelerin bir ana merkezle haberleşmesi zorunluluğu bulunmaktadır, aksi halde hesaplamalar değişimlerden sonra tekrar yapılarak rölelere aktarılamaz. Ayrıca arızanın her an gerçekleşebilme ihtimaline karşı haberleşmenin oldukça hızlı olması gerekmektedir. Böyle geniş ve hızlı bir haberleşme ağını kurduktan sonra entegre korumanın uygulanması klasik koruma metodlarına göre daha kolay ve hızlı olur. Entegre koruma sistemi aynı baraya bağlı kesicilerin bir entegre röle tarafından kontrol edildiği ve bütün entegre rölelerin bir merkezle haberleşerek çalıştığı bir sistemdir. Bu sistemin daha hızlı olması istenirse entegre rölelerin birbirleriyle haberleşmesi de sağlanabilir. Bu durumda entegre röleler kendi baralarından aldıkları ölçümleri ve diğer entegre rölelerin ölçümlerini karşılaştırarak arızayı ve arızanın yerini kısa sürede tespit edebilirler. Bu sistemde röle koordinasyonu için fazladan bir ayara ihtiyaç duyulmaz. Bütün bunlar dikkate alındığında, mikroşebekeler için adaptif-entegre bir koruma sisteminin yönlü aşırı akım röleleriyle oluşturulmuş geleneksel bir sisteme göre korumanın seçiciliği ve güvenilirliği açısından daha avantajlı olduğu söylenebilir. Ancak, merkezi bir kontrol ünitesine bağlı haberleşme özelliğine sahip bir koruma sistemi yönlü aşırı akım röleleriyle oluşturulmuş geleneksel bir sisteminden daha karmaşıktır. Bu sebeple, mikroşebekeleri korumak amacıyla adaptif-entegre bir koruma sisteminin tercih edilmesinin daha uygun olacağının gösterilmesi gerekmektedir. Karşılaştımanın yapılabilmesi amacıyla örnek bir mikroşebeke modellenmiş ve bu şebekede her iki koruma sistemi de uygulanmıştır. Örnek mikroşebeke normal durumda şebekeye bağlı olarak çalışmaktadır, ayrıca güç adası modunda da çalışabilmektedir. Aslına uygun bir örnek teşkil etmesi için güneş enerjisi santrali, rüzgar türbini ve biyogaz tesisi gibi yenilenebilir enerji kaynakları ve çeşitli güçlerde yüklerden oluşturulmuştur. Örnek sistemin normal çalışma durumu maksimum yükte çalışma olarak belirlenmiş ve koruma sistemlerinin ilk ayarları bu duruma göre yapılmıştır. Geleneksel koruma sisteminde bu ayarlar her durum için sabit kalırken adaptif-entegre koruma sistemi farklı durumlara göre rölelerin akım ayar değerlerini (IS) belirli bir algoritma yardımıyla değiştirmektedir. Koruma sistemlerinin karşılaştırılması için dört farklı durum belirlenmiştir. Bu durumlar normal çalışma, bir kısım yüklerin devreden çıkarılması, yerel kaynaklardan birinin devreden çıkarılması ve güç adası modunda çalışma durumlarıdır. Bütün bu durumlar için 1 numaralı hatta 3 faz, faz faz, faz faz toprak ve tek faz toprak arızaları gerçekleştirilmiştir. Yönlü aşırı akım röleleri (YAAR) ile uygulanan geleneksel korumanın koordinasyonu, arızanın gerçekleştiği hattın iki ucundaki rölelerin yedek korumayı sağlayan diğer hatlardaki rölelerden daha önce kesicilere açma sinyali göndermesi esasına dayanır. Bu durumda hatalı açma sinyallerini önlemek için sistemdeki ekipmanların özelliklerine bağlı olarak yedek koruma ile birincil koruma arasında belirli bir zaman aralığı bulunması gerekir. Örnek sistemde bu zaman aralığı 300 - 350 ms olarak belirlenmiştir. Adaptif-entegre koruma sisteminde ise hatların korunması, akım yönlerinin karşılaştırılması prensibine dayanmaktadır. Bu durumda arızayı tespit eden entegre aşırı akım rölesi (EAR) komşu EAR'lerle haberleşerek yön sorgulaması yapar. Her iki EAR tarafından da hattın ortasına doğru akan akım tespit edilirse arıza da tespit edilmiş olacaktır. Normal çalışma ve bir kısım yüklerin devreden çıkarılması durumlarında her iki koruma sistemi de beklendiği üzere doğru bir biçimde çalışmıştır. Sistemde değişiklik olmasına rağmen ikinci durumda da YAAR ile geleneksel korumanın doğru biçimde çalışmasının sebebi, yüklerin devreden çıkarılmasının arıza durumunda akan akım üzerindeki sınırlı etkisidir. Ancak, yerel kaynaklardan birinin devreden çıkarılması ve güç adası modunda çalışma durumlarında YAAR kullanılarak oluşturulan sistem seçicilik ve güvenilirlik konusunda başarısız olmuştur. Adaptif-entegre koruma sistemi ise her iki durumda da başarılı bir şekilde çalışmaya devam etmiştir. Sonuç olarak, mikroşebekelerde adaptif-entegre koruma sisteminin YAAR ile oluşturulan geleneksel koruma sisteminden daha başarılı bir koruma sağladığı bu çalışmayla beraber gösterilmiştir., Many individuals or institutions produce their own electricity, after renewable energy sources become more efficient and more accessible. Moreover, transmitting electrical energy produced by central high-powered plants to rural areas that are far away from city centers is considerably costly operation. These basic reasons lead to microgrid concept. The objective of microgrids is producing electricity and transmitting it to surrounding loads, similar to the large networks. However, microgrids are smaller than these networks, in addition to; they contain many distributed energy resources. These distributed energy resources are generally low-power sources, such as solar panels, wind turbines, biogas plants, and various energy storage units. Microgrids can operate with only these kinds of low-power distributed energy resources called as microgenerators and various types of loads or they can operate while connected to a main network. Microgrids transfer the excess energy to the main network during grid-connected mode. If the energy produced by local sources is insufficient for local loads, microgrids take energy form the main network. The connection between microgrid and main network can be interrupted on purpose or under emergency. Thus, microgrid operates in island mode. If a microgrid is operated by proper control and protection systems, then operating in island mode cause no issues. Otherwise, the system will not operate in the correct way, major changes will occur in frequency and voltage values. Power flow in microgrids can alternate greatly because microgrids generally contain more than one source, operate with renewable energy sources produces quite variable power and have two different operation modes that are grid-connected and island mode. Therefore, control and protection of the microgrids are more difficult than the traditional networks that have radial structure. Traditional directional overcurrent protection is a widespread method for protection and it is generally sufficient for protecting large networks. Relays that are used in this protection method determine faults by analyzing the amplitude of current. Direction of the current aids the relay while it determines whether the fault occur in the protection zone or not. If inverse time overcurrent relays are used as the sample microgrid system, operation time of the relays can be set to change depending on the amplitude of the current. Coordination time intervals are used between the consecutive relays for the coordination of inverse time overcurrent relays. IS and TMS values are set properly to determine the minimum limit value for sensing the fault and to apply coordination time intervals. Set values of this type of relays that have no communication line between each other or a central control unit can only be changed manually, this operation can not occur automatically. Therefore, this traditional protection method can not be applied on the networks that have frequently alternating load flow. For frequently alternating load flow condition of the network, a protection system that can adapt itself to this condition should be applied. This protection system is called as adaptive protection system. Adaptive protection system tracks the current values and circuit breaker (CB) status of the network. If a major change is determined by the protection system, then the system calculates load flow again and changes the set values of the relays depending on the load flow. To apply adaptive protection system on a network, relays should communicate with a central unit. Otherwise, new set values calculated after changes can not be transferred to the relays. Moreover, communication should be fast because the fault can occur at any moment. After establishing a fast and wide communication network, applying integrated protection will be faster and easier than conventional protection methods. Integrated protection system is a relatively new type of protection system that all CBs connected to same bus are controlled by an integrated relay and all integrated relays in the protection system communicate with a central unit while operating. If integrated relays communicate each other, then the system will operate faster. In this way, integrated relays compares the measurements taken from their own buses and the measurements of the other integrated relays to detect the fault and location of the fault in a short time. Additional set value is not needed for the relay coordination for this system. When all these characteristics are taken into consideration, an adaptive-integrated protection system will be more successful than a traditional protection system consisted by directional overcurrent relays in terms of selectivity and reliability. On the other hand, it is obvious that implementation of a protection system connected to central unit with a communication feature is more difficult than implementation of a traditional protection system consisted by directional overcurrent relays without communication. Therefore, it should be revealed that to prefer adaptive-integrated protection system is more proper way to protect microgrids. To compare these two protection systems, a microgrid is modeled on the MATLAB environment using Simulink tools and both of the protection systems are applied on the microgrid. Sample microgrid network operates in grid-connected mode normally; it can also operate in island mode. To constitute a realistic example, the sample microgrid contains renewable energy resources such as solar power plant, wind turbine and biogas plant and loads that have various amount of power consumption. Normal operation condition of the sample microgrid is determined as operating at maximum load, then set values of the protection systems are calculated according to this condition. Whereas the set values remain stable for all conditions for the traditional protection system, current pick up values (IS) of the integrated relays by means of a predetermined algorithm for adaptive-integrated protection system. Four different cases are determined for the comparison of the protection systems. These cases are normal operation, switching of certain loads, switching of one of the local sources, island mode operation. For all these conditions, 3 phase, phase to phase, phase to phase ground and single phase to ground faults are performed on the Line 1. The coordination of the traditional protection with directional overcurrent relays are based on the primary protection and back-up protection concepts. Whenever a line fault is detected, CBs that located on the both end of the line are expected to trip. If primary protection can not clear the fault, then back-up protection will operate. There should be a certain time interval between primary and back-up protection that is determined depending on the properties of the network equipments to prevent CBs from faulty tripping. This time interval is determined 300 - 350 ms for the sample network. Line protection is based on the comparison of the current directions for the adaptive-integrated protection system. In this case, the integrated overcurrent relay (IOR) that detects the fault communicates with neighbor IORs for direction comparison. If two IORs located on the both end of a line detect current flowing through opposite directions, then the location of the fault will be confirmed. Both of the protection systems are operated correctly during first two cases, normal operation and switching of certain loads as expected. Main reason of the correct operation of traditional protection with directional overcurrent relays (DOR) despite the changes in the system is the limited effect of load switching on the fault current. However, traditional protection that consists of DORs fails in terms of selectivity and reliability during last two cases whereas adaptive-integrated protection system manage to operate successfully in both cases. As a result, this study presents that adaptive-integrated protection system is more successful than traditional protection system with directional overcurrent relays (DOR) for microgrids., Yüksek Lisans, M.Sc.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-20T22:58:46Z No. of bitstreams: 1 JAMILE PINHEIRO NASCIMENTO - DISSERTAÇÃO PPGEE 2014..pdf: 2146495 bytes, checksum: e397e112357d55c0badad1a62f5324cf (MD5) Made available in DSpace on 2018-04-20T22:58:46Z (GMT). No. of bitstreams: 1 JAMILE PINHEIRO NASCIMENTO - DISSERTAÇÃO PPGEE 2014..pdf: 2146495 bytes, checksum: e397e112357d55c0badad1a62f5324cf (MD5) Previous issue date: 2014-08 Um algoritmo de proteção adaptativa para solucionar o problema da proteção de sistemas com geração distribuída é proposto. O algoritmo modifica as configurações dos relés de forma on-line, utilizando como informação de entrada, os estados dos disjuntores. Ao final, constatou-se que mesmo com a entrada ou saída dos geradores distribuídos, o sistema de distribuição continuou a ser protegido. Para validar o algoritmo utilizou-se um sistema-teste do IEEE e o Real Time Digital Simulator (RTDS). An adaptive protection algorithm to solve protecting systems with distributed generation problem is proposed. The algorithm modifies relays settings on on-line form, using circuit breakers state as input information. At the end, it was found that even with the input or output of distributed generators, distribution system continued to be protected. To validate the algorithm it was used an IEEE test system and the Real Time Digital Simulator (RTDS).

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2014, Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2014, Elektrik dağıtım sistemi işleticileri, elektrik enerjisini ekonomik olarak kabul edilebilir maliyetlerle ve mümkün olan asgari kesinti süresi ve sıklığı ile kullanıcılarına sunabilmeleri gerekmektedir. Ancak, elektrik dağıtım şebekelerinin tasarımı ve yapımı ne kadar iyi olursa olsun işletilmeleri sırasında çeşitli hatalar ve arızalar ile karşılaşılmaktadır. Ortaya çıkan hatalar ve arızaların hem şebeke elemanlarına etkilerinin en aza indirilmesi hem de insan hayatına ilişkin tehlikeyi sınırlamak için koruma sistemleri kullanılmaktadır. Son yıllarda hızla artan yenilenebilir enerji kaynakları elektrik dağıtım sistemlerine orta gerilim ve alçak gerilim seviyesinde bağlanmaktadır. Tek yönlü enerji akışına göre tasarlanmış ve işletilen elektrik dağıtım şebekelerine bağlanan dağıtık üretim kaynakları yeni problemler ortaya çıkartmaktadır. Ortaya çıkan bu problemlerin aşılması yenilenebilir kaynakların yaygınlaşması bakımından da önem arz etmektedir. Günümüzde haberleşme teknolojileri gelişerek birçok elektronik cihazda uygulanabilir hale gelmiştir. Bu yenilik koruma rölelerinde de uygulanmış ve farklı haberleşme protokollerine sahip sayısal koruma rölelerinin ortaya çıkmasını sağlamıştır. Bu sayede koruma röleleri daha esnek, akıllı ve üstün özelliklere sahip olmuşlardır. Sayısal koruma röleleri sahip oldukları haberleşme imkânları sayesinde, klasik koruma sistemlerinin yetersiz kalıp hatalı çalışma yaptığı durumlar için çözümler sunabilmektedir. Koruma yaptıkları bölgedeki ekipmanların pozisyonlarından ve sistemin durumundan haberdar olarak çalışabilen koruma röleleri, mevcut koruma parametrelerini sistemin durumuna göre değiştirebilirler. Böylece koruma sistemlerini dinamik hale getirip, adaptif bir koruma sistemi olmasını sağlarlar. Adaptif koruma sistemleri özellikle birden fazla beslenme senaryosuna sahip olan dağıtım sistemlerinde hatalı çalışmaların önüne geçmek için çözüm olmaktadır. Bunun yanı sıra, mevsimsel yük değişiminin fazla olduğu, yeniden yapılandırmalara açık olan ve ihtiyaç halinde generatörlerin devreye girip çıktığı sistemlerde de adaptif koruma sistemleri kullanılabilir. Adaptif koruma sistemlerindeki koruma röleleri farklı senaryolar için farklı ayar gruplarını kullanabilir. Bu sayede koruma sisteminin, elektrik dağıtım sisteminin durumuna en uygun koruma parametreleri ile çalışmasını sağlayarak güvenirliliği arttırırlar. Adaptif koruma sistemleri tasarlanırken ilk olarak, elektrik dağıtım sisteminin çalışma senaryoları oluşturulur. Her bir senaryo için arıza analizleri yapılarak koruma parametreleri hesaplanır ve ayrı ayrı gruplanır. Böylece senaryo sayısı kadar ayar grup sayısı elde edilir. Bu işlemin ardından ayar grupları koruma rölelerinde tanımlanır. Sistemin senaryolarına uygun ayar gruplarının koruma rölelerinde aktif hale getirilebilmesi için, akıllı bir cihaz ya da sisteme oluşturulan tüm senaryolar tanımlanır. Bu görevi yapması için SCADA sisteminden faydalanılabilir. SCADA sistemi önceden belirlenmiş olan senaryolar gerçekleştiğinde koruma rölelerine komut yollayarak koruma ayar grubunu değiştirir. Böylece koruma sisteminin dinamik bir yapıda olması sağlanarak, dağıtım sistemini adaptif olarak koruması gerçekleştirilir. Bu tez çalışmasında klasik koruma sistemlerinin yetersiz kaldığı durumlar örnek dağıtım sistemleri kullanılarak incelenmiştir. Hatalı çalışmaların önüne geçebilmek için klasik koruma sistemleri yerine dinamik bir yapıya sahip olan adaptif koruma sistemlerinin kullanılması gerektiği vurgulanmıştır. Adaptif koruma sistemlerinin klasik koruma sistemlerinden daha etkin koruma yaptığı savunulmuştur. Bununla beraber bu çalışmada klasik koruma sistemi ile korunan, işletme manevralarına bağlı olarak, farklı beslenme durumlarına sahip olan gerçek bir elektrik dağıtım sisteminin hatalı çalışma problemi ele alınmıştır. Bu problemi çözmek için, elektrik dağıtım sisteminin tüm çalışma senaryoları oluşturulup SINCAL yazılımında senaryolara ait kısa devre arıza analizleri yapılmıştır. Analiz sonuçları ve kullanılan ekipmanların katalog bilgileri göz önüne alınarak senaryo adedince koruma ayar grupları oluşturulmuştur. Oluşturulan bu ayar grupları SICAM 230 SCADA yazılımında da tanımlanarak, uygun şartlar oluştuğunda koruma rölelerinde otomatik olarak aktif hale gelmesi sağlanmıştır., Electrical distribution system operators should be able to provide electrical energy to their users with economically acceptable cost and the minimum possible duration and frequency of interruption. However, the design and construction of the electrical distribution network has done correctly, they encounter various faults and failures during their operation. Protection systems are used to minimize the effects of these faults to other network elements and danger on human life. Protection systems aim to detect fault and fault type for continuity of energy. In order to fullfill this task, protection systems must work with high speed, reliability and selectivity. All of these properties are provided by correct protection relay coordination. Unfortunately, although protection relays have a correct coordination, in some special situations they can not work correctly. For instance, whenever protection area which is under the responsibility of relay is changed, protection relay starts to work incorrectly. One of the common problems about this issue occur when electric distribution system’s operating status is changed from “open ring” to “close ring” or opposite. Open ring or close ring state operations directly cause a change in short-circuit current value. For instance in case of any fault, if electric distribution system is being operated in “open ring” and has a magnitude of 1A fault current; it will has a more than 1A fault current in “close ring”. Thus, protection relays must have more than one protection parameter for open ring and closed ring to work correctly. Moreover, at areas, where are affecting from weather conditionals a lot, have problems about protection relay coordination. This is why, at summer time consume of electricity is greater than at winter time. Therefore, if the protection system is designed for winter time, it will make wrong operations at summer time. To solve this problem protection system must have two setting groups for each season. In addition, to reduce the inrush current of asynchronous machines, capacitors are connected parallel to the induction machines. This additional paralel connection affects the protection system negatively because it changes the magnitude of the inrush current. When asynchronous machine has a capacitor bank; current value, which comes from network, decreases. As a result, capacitor bank changes the protection settings of protection relay. Furthermore, synchronous generators’ synchronization relays must compare and check the magnitude of the voltage. Unfortunately, this value is not fixed and depends on the state of the circuit breakers which are connected the generator. To achieve this problem, synchronization relays must be informed the position of circuit breakers’ position and use different setting groups to measure and compare the voltage magnitude. Other problem about synchronous generator is changes in generator mode. Basically, generator has two operating modes. One of them is “parallel mode with network”, other one is “island mode”. At island mode, generator only feeds the loads and doesn’t export to network active power. While working this independent mode, generator’s protection parameters about time settings are shorter than parallel mode. Having two different time settings and one protection relay, requires the use of two different setting groups. What is more, diesel generators which are used for backup power system, change the electrical network’s short circuit power. So that, number of active diesel generator directly changes the magnitude of short circuit current. In this case, number of protection relays’ setting group must be equal the number of the diesel generator which can be active whenever necessary. Protection relays are expected to continue their tasks in these different situations. In other words, protection relays must not be affected from the changes in the structure of its protection zone. To achieve this, protection relays should notice the changes in their protection zone. In recent years, the rapidly growing renewable energy sources to the electricity distribution system is connected to the medium voltage and low voltage level, which were designed for one-way flow of energy primarily. This growth has created new problems of distributed generation sources. To overcome these problems is a vital importance. Today, communication technology has developed to be applicable in many electronic devices. This innovation also applied in the protection relay and different communication protocols has led to the emergence of numerical protection relays. In this way, protection relays have become more flexible, intelligent and outstanding features. Thanks to communication facilities they have, numerical protection relays provide solutions to situations in which a malfunction can be made by insufficient mold of conventional and classical protection systems. Depending on the state of the system and their position in the region, the system will know the status of equipment that can function and current protection parameters may change as a result. This leads protection systems to become dynamic and be an adaptive system. Adaptive protection systems, especially in the distribution systems which have multiple operational scenarios, are the solution in order to prevent faulty operation. In addition to this, systems where seasonal load changes or re- configurations occur are in need of adaptive protection systems. Adaptive protection system protection relays can use different settings for different scenarios. By the condition of the network, protection system will provide optimum protection parameters, so the reliability of the sistem will be increased. When designing a adaptive protection system first of all, electrical distribution system’s operating scenarios are created. Protection parameters for each scenario are calculated and analyzed and grouped separately. Thus, number of the setting groups and number of the scenarios will be same. Following this transaction, setting groups are defined to protection relays. To work with the optimal setting group, which belongs to the scenario of the electrical distribution system, intelligent device or system should be used. To do this task, SCADA systems may be utilized. SCADA system is able to send the commands to protection relays, when the pre-defined scenarios are occurred. Thus, protection relay’s setting groups are changed automatically by SCADA system. Thereby ensuring that the dynamic structure of the protection system, distribution system protection is provided adaptively. In this thesis, classic protection system’s failure situations were investigated by using sample electric distribution systems. In addition it was emphasized that, in order to prevent mis-operations, instead of using classic protection systems, adaptive protection system which has a dynamic structure should be used. Moreover, it was argued that, adaptive protection systems are more effective than the classic protection systems. Furthermore, in this study problem of mis-operations in real electric distribution system, which has a classic protection system and has a different feeding scenario, was discussed. To solve this problem, the whole operation scenarios of the electric distribution system scenarios were created and short-circuit fault analysis were performed for all scenarios by using SINCAL software. According to results of the analysis and the catalog information of the equipments, setting groups were created. These setting groups are also defined in SICAM 230 SCADA software. Thus, when the conditions are suitable to change the setting group of protection relays, SCADA provides this change automatically., Yüksek Lisans, M.Sc.

This paper proposes a framework for adaptive feeder protection in distribution grids with a high amount of distributed generators (DGs) installed. The scheme adapts the feeder protection relay settings according to the changes in the connection status of those DGs that have a significant impact on the fault current. The core of the method consists in the identification of the connection status of the DGs using an iterative modified state estimation (SE) program. The approach is illustrated using a realistic 31-node distribution network model.

The electrical distribution system in the United States is considered one of the most complicated machines in existence. Electrical phenomena in such a complex system can inflict serious self-harm. This requires damage prevention from protection schemes. Until recently, there was a safe gap between capacity to deliver power and the demand. Therefore, these protection schemes focused on dependability allowing the disconnection of lines, transformers, or other devices with the purpose of isolating the faulted element. On some occasions, the disconnections made were not necessary. The other extreme of reliability calls for security. This aspect of reliability calls for the operation of the protective devices only for faults within the intended area of protection. There is a tradeoff here; where a dependable protection scheme will assuredly prevent damage, it is prone to unnecessary operation which can lead to cascading outages. Where a secure scheme will not operate unnecessarily, it is prone to pieces of the system becoming damaged when relays fail to operate properly. With microprocessor based relaying schemes, a hybrid reliability focus is attainable through adaptive relaying. Adaptive relaying describes protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system. These adjustments can help to avoid relay miss-operation. Adjustments could include, but are not limited to, the logging of data for post-mortem analysis, communication throughout the system, as well changing relay parameters. Several concepts will be discussed, one of which will be implemented to prove the value of the new tools available. Master of Science

Today's electric power system is operated under increasingly stressed conditions. As electrical demand increases, the existing grid is operated closer to its stable operating limits while maintaining high reliability of electric power delivery to its customers. Protective schemes are designed to account for pressures towards unstable operation, but there is always a tradeoff between security and dependability of this protection. Adaptive relaying schemes that can change or modify their operation based on prevailing system conditions are an example of a protective scheme increasing reliability of the power system. The purpose of this thesis is to validate and analyze implementation of the Security-Dependability Adaptive Voting Scheme. It is demonstrated that this scheme can be implemented with a select few Phasor Measurement Units (PMUs) reporting positive sequence currents to a Phasor Data Concentrator (PDC). At the PDC, the state of the power system is defined as Stressed or Safe and a set of relays either vote or perform normal operation, respectively. The Adaptive Voting Scheme was implemented using two configurations: hardware- and software-based PDC solutions. Each was shown to be functional, effective, and practical for implementation. Practicality was based on the latency of Wide Area Measurement (WAM) devices and the added latency of relay voting operation during Stressed conditions. Phasor Measurement Units (PMUs), Phasor Data Concentrators (PDCs), and relay operation delays were quantified to determine the benefits and limitations of WAMS protection and implementation of the voting scheme. It is proposed that the delays injected into the existing protection schemes would have minimal effect on the voting scheme but must be accounted for when implementing power system controls due to the real-time requirements of the data. Master of Science

With the continuously increasing power demands, the power system is much closer to its limits. As a result, the power system is more vulnerable to disturbances and faults. The voltage instability is one of the main reasons of cascading trip, wide-area blackout, and even the system-wide voltage collapse. In this paper, the online load identification using measurement- based approach based on Phasor Measurement Units (PMU) was proposed to evaluate the proximity to voltage instability in order to prevent voltage collapse. In the scenarios of disturbances, the proximity to voltage collapse with respect to load characteristics was evaluated. Based on different load characteristics, different control and protection schemes were implemented, i.e. shunt capacitor connection, on-load tap changer blocking and load shedding. The results showed that load-based adaptive voltage control and protection scheme based on PMUs is promising, as it prevented the voltage collapse and minimized the load shedding area.

A significant increase in the penetration of distributed generation has resulted in a possibility of operating distribution systems with distributed generation in islanded mode. However, overcurrent protection of an islanded distribution system is still an issue due to the difference in fault current when the distribution system is connected to the grid and when it is islanded. This paper proposes the use of adaptive protection, using local information, to overcome the challenges of the overcurrent protection in distribution systems with distributed generation. The trip characteristics of the relays are updated by detecting operating states (grid connected or island) and the faulted section. The paper also proposes faulted section detection using time overcurrent characteristics of the protective relays. Simulation results show that the operating state and faulted section can be correctly identified and the protection system settings can be updated to clear the faults faster.

As the world moves further into the 21st century, the electricity demand worldwide continues to rapidly grow. The power systems that supply this growing demand continue to be pushed closer to their limits. When those limits are exceeded, system blackouts occur that have massive societal and economical impact. Power system protection relays make up a piece of these limits and can be important factors in preventing or causing a system blackout. The purpose of this thesis is to present a working implementation of an adaptive protection scheme known as the adaptive voting scheme, used to alter the security/dependability balance of protection schemes. It is argued that as power system conditions change, the ability of protection relays to adjust the security/dependability balance based on those conditions can allow relays to play a part in preventing power system catastrophes. It is shown that the adaptive voting scheme can be implemented on existing protection technology given Wide Area Measurements (WAMs) provided by Phasor Measurement Units (PMUs). The proposed implementation characteristics allow numerous existing protection practices to be used without changing the basic operation of the practices. Master of Science

Voltage control, grid reconfiguration and adaptive protection are considered in this paper since they are representative of the various control applications in the context of smart grids which can make significant use of the information and communication technology. All the three control applications have multiple objectives of which some are conflicting and these call for the use of multi-­objective optimization in implementing the controls. The presence of non convex objectives and constraints calls for the use of evolutionary algorithms in solving the control problems. This paper enlists the generally dealt objectives and constraints for the three control applications. The presence of distributed generators in smart grids brings in factors that need additional consideration in solving the multi-­objective optimization. The paper proposes that genetic algorithm is likely to be a good optimization technique in achieving the control objectives, the reasons for which are qualitatively described in this paper along with the challenges in using genetic algorithm. ispartof: pages:26- ispartof: Proceedings of the 2011 IEEE International Conference on Networking, Sensing and Control, pages:26- ispartof: 2011 IEEE International Conference on Networking, Sensing and Control, location:Delft, Netherlands date:11 Apr - 13 Apr 2011 status: published

Throughout the history of power system protection, researchers have strived to increase sensitivity and speed of apparatus protection systems without compromising security. With the significant technological advances in wide-area measurement systems, for transmission system protection, current differential protection scheme outscores alternatives like overcurrent and distance protection schemes. Therefore, in this paper, we address this challenge by proposing a methodology for adaptive control of the restraining region in a current differential plane. First an error analysis of conventional phasor approach for current differential protection is provided using the concept of dynamic phasor. Subsequently, we extend the methodology for protection of series compensated transmission lines. Finally, we also evaluate the speed versus accuracy conflict using phasorlets. Electromagnetic Transient Program simulations are used to substantiate the claims. The results demonstrate the utility of the proposed approach.

The differences between shipboard and land based power systems are explored to support the main focus of this work. A model was developed for simulating hidden failures on shipboard integrated propulsion plants, IPP. The model was then used to evaluate the segregation of the IPP high voltage, HV, buses in a similar fashion as a shipboard firemain. The HV buses were segregated when loss of propulsion power would put the ship as risk. This new treatment reduces the region of vulnerability by providing a high impedance boundary that limits the effects of a hidden failure of a current magnitude or differential based protective element, without the installation of any additional hardware or software. It is shown that this protection could be further improved through the use of a simple adaptive protection scheme that disarms unneeded protective elements in certain configurations. Master of Science

The power industry is currently in the process of re-inventing itself. The unbundling of the traditional monopolistic structure that gave birth to a deregulated electricity market, the mass tendency towards a greener use of energy, the new emphasis on distributed generation and alternative renewable resources, and new emerging technologies have revolutionized the century old industry. Recent blackouts offer testimonies of the crucial role played by protection relays in a reliable power system. It is argued that embracing the paradigm shift of adaptive protection is a fundamental step towards a reliable power grid. The adaptive philosophy of protection systems acknowledges that relays may change their characteristics in order to tailor their operation to prevailing system conditions. The purpose of this dissertation is to present methodology to implement a security/dependability adaptive protection scheme. It is argued that the likelihood of hidden failures and potential cascading events can be significantly reduced by adjusting the security/dependability balance of protection systems to better suit prevailing system conditions. The proposed methodology is based on Wide Area Measurements (WAMs) obtained with the aid of Phasor Measurement Units (PMUs). A Data Mining algorithm known as Decision Trees is used to classify the power system state and to predict the optimal security/dependability bias of a critical protection scheme. Ph. D.

The idea of performing power systems dynamic analysis in the power-angle domain has been hinted at by previous researchers, but this may be the first published document to develop detailed techniques by which entire power systems can be represented and solved in the power-angle domain. With the widespread deployment of phasor measurement units and frequency data recorders the industry is looking for more real-time analytical tools to turn real-time wide-area measurements into useful information. Applications based on power-angle domain analysis are simple enough that they may be used online. Power-angle domain analysis is similar to DC load-flow techniques in that a flat voltage profile is used and it is assumed that real power and voltage angle are completely decoupled from reactive power and voltage magnitude. The linearized equations for the dynamics of generators and loads are included in the model, which allows the electromechanical response to be solved using conventional circuit analysis techniques. The effect of generation trips, load switching, and line switching can be quickly approximated with nodal analysis or mesh analysis in the power-angle domain. The analysis techniques developed here are not intended to be as accurate as time-domain simulation, but they are simpler and fast enough to be put online, and they also provide a better analytical insight into the system. Power-angle domain analysis enables applications that are not readily available with conventional techniques, such as the estimation of electromechanical propagation delays based on system parameters, the formulation of electromechanical equivalents, modal analysis, stability analysis, and event location and identification based on a small number of angle or frequency measurements. Fault studies and contingency analysis are typically performed with detailed time-domain simulations, where the electromechanical response of the system is a function of every machine in the interconnection and the lines connecting them. All of this information is rarely known for the entire system for each operating condition; as a result, for many applications it may be more suitable to compute an approximation of the system response based on the current operating state of only the major lines and generators. Power-angle domain analysis is adept at performing such approximations. Ph. D.

This paper elaborates settings and modification of the operating characteristic of adaptive distance relay which protects double-circuit lines. The zero sequence mutual coupling of parallel circuits carry error into the relay impedance measuring. So there are two possible behaviors of distance relay: underreach and overreach depending on the operating mode. This paper proposes adaptive model which solves problems of single-line-to-ground fault on a single line. Input values are local measurements such as voltage and current plus the transmission line theory, and the output is signal for the distance relay whether it must trip or must not trip. As part of the adaptive model it is implemented self-organizing neural network - Kohonen network. The developed model offers solution for distance protection of a double-circuit transmission lines.

he scalable video coding extension of H.265/High Efficiency Video Coding (HEVC) is capable of supporting diverse video resolutions. Due to the fact that the Enhancement Layer (EL) is encoded and decoded with the aid of the Base Layer (BL), the decodability of ELs is conditioned on that of the BL. Hence the EL frames occasionally have to be discarded as a result of corrupted BL frames. Therefore, potent Unequal Error Protection (UEP) schemes have been conceived for providing a stronger protection to the BL by invoking a lower coding rate based Forward Error Correction (FEC) or a higher transmit power for a specific Multiple-Input Multiple-Output (MIMO) sub-channel. This stronger protection is essential for the BL for the sake of both avoiding the waste of resources caused by the dropped undecodable EL bits and for improving the reconstructed video quality. In this treatise, we propose an adaptive system for transmitting the layered video bit stream over the wireless channel. The proposed system is capable of selecting an appropriate interlayer (IL) operation-aided FEC (IL-FEC) scheme in order to maintain the robustness of the system by comparing the near-instantaneous Signal-to-Noise Ratio (SNR) to pre-recorded reconfiguration thresholds. Our simulation results show that the proposed adaptive system is capable of providing better video quality over a large proportion of the channel Signal-to-Noise Ratio (SNR) range than its corresponding fixed-mode counterparts.

It is expected that future power systems will require radical distributed control approaches to accommodate the significant expansion of renewable energy sources and other flexible grid devices. It is important to rapidly and efficiently respond to disturbances by, for example: utilising adaptive, wide-area protection schemes; proactive control of available grid resources (such as managing the fault level contribution from converter-interfaced generation) to optimise protection functionality; and taking post-fault action to ensure protection stability and optimal system operation. This paper analyses and highlights the protection functions which will be especially important to minimising the impact of disturbances in future power systems. These functions include: fast-acting wide-area protection methods using Phasor Measurement Units (PMUs); adaptive and “self-organising” protection under varying system conditions; protection with distributed Intelligent Electronic Devices (IEDs); enhanced fault ride-through; and pattern recognition based schemes. In particular, the paper illustrates how the increased availability of measurements and communications can enable improved protection functionality within distribution systems, which is especially important to accommodate the connection of highly-distributed generation at medium- and low-voltages.

The increasing penetration of dispersed generation (DG) brings challenges to conventional protection approaches of distribution system, mainly due to bi-directional power flow and variable fault current contribution from different generation technology-based DG units. Moreover, the trend of allowing islanded operation of distribution systems necessitates the adoption of adaptive protection methods for distribution systems. In order to improve the reliability and selectivity of protection for such kind of distribution systems, a coordinative adaptive protection based on multi agent system (MAS) is proposed. The adaptive protection intelligently adopts suitable settings for the variation of fault current from diversified DG units. Furthermore, the structure of mobile MAS with additional flexibility is capable of adapting the changes of system topology in a short period, e.g. radial/meshed, grid-connected/islanded. The protection method is tested on a simplified distribution system model of Denmark in DIgSILENT/PowerFactory.

It is expected that future power systems will require radical distributed control approaches to accommodate the significant expansion of renewable energy sources and other flexible grid devices. It is important to rapidly and efficiently respond to disturbances by, for example: utilising adaptive, wide-area protection schemes; proactive control of available grid resources (such as managing the fault level contribution from converter-interfaced generation) to optimise protection functionality; and taking post-fault action to ensure protection stability and optimal system operation. This paper analyses and highlights the protection functions which will be especially important to minimising the impact of disturbances in future power systems. These functions include: fast-acting wide-area protection methods using Phasor Measurement Units (PMUs); adaptive and “self-organising” protection under varying system conditions; protection with distributed Intelligent Electronic Devices (IEDs); enhanced fault ride-through; and pattern recognition based schemes. In particular, the paper illustrates how the increased availability of measurements and communications can enable improved protection functionality within distribution systems, which is especially important to accommodate the connection of highly-distributed generation at medium- and low-voltages.