Yalıtkan kalınlığının ve tipinin kısmi boşalmaya etkisi
The effect of thickness and type of insulator on partial discharge
Yazar: EMRAH GÜNEŞ
Danışman: PROF. DR. ŞÜKRAN EMEL ÖNAL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Elektrik Mühendisliği Ana Bilim Dalı / Elektrik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering

Özet:
Elektriğin sorunsuz ve verimli bir şekilde üretilmesi, dağıtılması, iletilmesi elektrik mühendisliği için çok önemlidir. Elektrik sistemlerinin kararlığı sistemde kullanılan yüksek gerilim elemanlarıyla doğrudan ilişkilidir. Sistemde kullanılan yüksek gerilim elemanlarında oluşan problemler sistemin verimliliğini ve kararlılığını olumsuz yönde etkileyerek sistemin işleyişini bozar. Sistemdeki elemanlarda meydana gelen olaylardan biri de elektriksel boşalmalardır.
Elektriksel boşalmalar genel olarak "yük veya elektrikten kurtulma" olarak tanımlanır. Yalıtkan malzemeler normal koşullarda elektrik akımını iletmezler. Yalıtkan malzemenin elektriği iletir hale geçtiği durum olarak adlandırılan elektriksel boşalmalar, tam ve kısmi boşalmalar olmak üzere iki grupta incelenmektedir. 
Yapılan tez çalışmasında farklı boyutlardaki ve tipteki yalıtkan malzemeler kullanılarak, farklı tip ve boyutlardaki elektrot sistemleri kullanılarak, 2 farklı test yöntemi izlenerek, delinme gerilimi, kısmi boşalma başlangıç gerilimi gibi elektriksel büyüklükler elde edilmiş, bu bilgilerle yalıtkan malzemenin dielektrik açıdan kalitesi hakkında önemli bulgulara ulaşılmıştır.
Gerçekleştirilen çalışmada 25x25 mm disk elektrot, 25x75 mm disk elektrot, 150x150 mm disk elektrot düzenekleri kullanılmıştır. Yalıtkan malzeme olarak 200x200x1 mm, 200x200x2 mm, 200x200x3 mm ve 200x200x8 mm boyutlarında presboardlar, 50x10x10 mm ve 50x10x40 mm boyutlarında polyesterli lamine presboard ve kazeinli lamine presboard kullanılmıştır.
Deneysel çalışmalarda elektriksel dayanım testleri ve kısmi boşalma testleri üzerinde durulmuştur. Deneyler temelde 6 adet, fakat onlarca test içermektedir. İlk olarak 1, 2, 3, 8 mm kalınlıklardaki presboardlar yalıtkan malzeme olarak kullanılarak elektriksel dayanım testleri yapılmıştır. 10 ve 40 mm kalınlıklardaki polyesterli lamine presboard yalıtkan malzemeleriyle kısmi boşalma testleri gerçekleştirilmiştir. 1 ve 3 mm kalınlıktaki presboardlar üzerinde kısmi boşalma testleri yapılmıştır. 10 ve 40 mm kalınlıklardaki kazeinli lamine presboardlar üzerinde kısmi boşalma testleri gerçekleştirilmiştir. 10 mm kalınlıklardaki polyester ve kazein lamine presboardlar ile elektriksel dayanım testleri yapılmıştır. Son olarak 150x150 disk elektrot sistemi kullanılarak elektriksel dayanım testleri gerçekleştirilmiştir. 
Testler esnasında elde edilmesi gereken delinme gerilimi ve kısmi boşalma başlangıç gerilimlerini okuyup yorumlayabilmek için deney düzeneğinde bir kapasitif gerilim bölücü, bir kuplaj kapasitörü ve High Volt firmasının geliştirdiği ICMcompact kısmi boşalma dedektörü kullanılmıştır. Elde edilen veriler bilgisayardaki bir yazılım vasıtasıyla grafiklenip, tablolanmıştır.
Elde edilen deney sonuçlarının yorumlanması kısmı ise 3 bölümden oluşmaktadır. İlkinde, 1 ve 3 mm kalınlıklardaki presboardların elektriksel dayanım ve kısmi boşalma test sonuçlarını karşılaştırılmıştır. Böylece aynı tip ve aynı boyutlardaki malzemelerin farklı test tekniklerinden çıkan sonuçlar değerlenmiştir. İkinci olarak 10 ve 40 mm kalınlıklardaki polyesterli ve kazeinli lamine presboardların kısmi boşalma test sonuçları aynı kalınlık-farklı malzeme ve aynı malzeme-farklı kalınlık olmak üzere incelenmiştir. Bir diğer aşamada, 10 ve 40 mm kalınlıklardaki polyesterli ve kazeinli lamine presboardların elektriksel dayanım test sonuçları üzerine tartışılmıştır.
Yapılan deneyler ve deneylerden elde edilen verilerin incelenmesi sonucunda kısmi boşalma başlangıç geriliminin ve delinme geriliminin yalıtkan kalınlığından, yalıtkan tipinden, elektrot tipinden, test metodundan etkilendiği görülmüştür.

Abstract:
Producing, distributing and transmitting of electricity in a smooth and efficient manner is very important for electrical engineering. The stability of electrical systems is directly related to the high voltage elements used in the system. The problems in the high voltage components used in the system adversely affect the efficiency and stability of the system and impair the functioning of the system. One of the events occurring in the elements in the system is electrical discharges.
Electrical discharges are generally defined as " load or discharge from electricity". Insulating materials do not conduct electrical current under normal conditions. Electrical discharges, which are called as the condition where the insulating material transmits electricity, are examined in two groups as complete discharges and partial discharges. Also partial discharges are investigated different type of groups which are internal discharges, surface discharges, corona discharges and electrical treeing.
Partial discharge is an electrical discharge which does not fully bridge the insulation. Because of partial discharge have low magnitude in charge, it is called as a localized dielectric breakdown generally. Even though partial discharges are generally small in size, they can cause major problems and can cause deteriorating the material. So partial discharges are very important to control and they are also dangerous for the insulators in high voltage systems.
Problems due to partial discharges in high voltage systems lead to failures in the insulation of high voltage systems cause expensive and time consuming maintenance. Therefore, the determination of partial discharges and the analysis of partial discharge data are very important in preventing the problems that may occur in the insulation of high voltage systems. There are two main methods which are electrical and non-electrical methods to detect and analysis. Non-electrical methods are optical detection method, mechanic detection method and chemical detection method. Electrical method is one of the most popular methods for inspection of the partial discharge in high voltage systems.
Partial discharge signals were studied in the thesis and some experiments were carried out. Partial discharges are electrical discharges that affect the performance of an electrical system negatively. After that they may cause very big damage damage to the system. Therefore, it is many important that partial discharges and their magnitudes must be determined before possible failures.  
Lots of studies have been made about partial discharges to prevent the systems from the beginning of the nineteenth century to present day. Chemical, mechanic, optical and electrical methods were used in these studies, and also they had different experiment setup, different materials and analysis techniques respectively. 
In the thesis study, by using different types and sizes of electrode systems and using different size and type of insulating materials, following two different test methods, electrical magnitudes such as puncture voltage, partial discharge initial voltage have been obtained. With this information, important findings about the dielectric quality of insulating material have been reached.
In the first part of the thesis, aim of the thesis was explained, mentioned about literature review and the studies about the partial discharges in the last century, and hypothesis of the thesis study was specified. Second part includes theoric knowledge about the electrical discharge phenomena and it's types like complete and partial discharges which are internal discharges, surface discharges, corona discharges and electrical treeing. In third part, preparation before the tests was explained, the experiment setup and equipments were introduced. After that, 6 different experiments explained about how to do these and what type of insulators, electrodes, test methods used, and results of the tests were showed. In fourth part, test results compared to each other according to insulator thickness and insulator type. Fifth and the last part includes comments about study and tests result, and suggestions about the study.
Partial discharge measuring tests in this study are performed in an accredited high voltage laboratory. There are a high voltage transformer which has 40 kVA, 0,4/200 kV electrical properties to get the high voltage to the test system. Additionally, a resistor that is type of  50 kΩ, 125 kW features used for preventing the system from over current, and 150 pF, 200 kV capacitive voltage divider to measure the high voltage produced by transformer. To measure and analyze the partial discharge signals, 0,5 nF, 200 kV coupling capacitor and ICMcompact, partial discharge detector, are used. By using these equipments, all the partial discharge signals could be measured, analyzed and observed their effects on the insulators.   
In the study, 25x25 mm disc electrode, 25x75 mm disc electrode, 150x150 mm disc electrode assemblies were used. As an insulating material, 200x200x1 mm, 200x200x2 mm, 200x200x3 mm and 200x200x8 mm sized pressboards, 50x10x10 mm and 50x10x40 mm sized polyester laminated pressboard and casein laminated pressboard were used. In experimental studies, electrical strength tests and partial discharge tests are emphasized. Experiments basically contain 6 pieces, but in dozens of tests.
In the study, two different test methods were used which are electrical resistance test (BDV) and partial discharge test (PDIV). At the end of the whole experiments, results of the tests are compared to each other and interpreted in terms of effects of insulator type and thickness on partial discarge. 
Firstly, the electrical resistance tests were done by using the pressboards in thicknesses of 1, 2, 3, 8 mm as insulating material. Partial discharge tests were carried out with 10 and 40 mm thickness polyester laminated pressboard insulating materials. Partial discharge tests were made on 1 and 3 mm thickness presboard. Partial discharge tests were performed on casein laminated pressboards in thicknesses of 10 and 40 mm. Electrical resistance tests were made with polyester and casein laminated pressboards in thicknesses of 10 mm.
In the experiment part, two types of tests methods which are breakdown voltage test (BDV) and partial discharge inception voltage test (PDIV) were used. Both of these tests applied according to IEC standarts which are test tecniques, insulator types and thicknesses, electrode types, transformer oil, test equipments, even preparation before the tests.
During the tests, a capacitive voltage divider, a coupling capacitor and an ICMcompact partial discharge detector developed by High Volt company were used in the test setup to read and interpret the puncture voltage and partial discharge initial voltages to be obtained. The datas obtained are graphed and plotted by means of a software in the computer.
The interpretation of the obtained test results consists of 3 parts. 
In the first of the final part, the electrical resistance and partial discharge test results of the 1 and 3 mm thickness presses were compared. Thus, the results obtained from different test techniques of materials of the same type and size were evaluated. Secondly, partial discharge test results of polyester and casein laminated pressboards with thicknesses of 10 and 40 mm were examined with the same thickness-different material and the same material-different thickness. In the another stage, the electrical strength test results of polyester and casein laminated pressboards with thicknesses of 10 and 40 mm were discussed. 
As a result of the experiments and the data obtained from the experiments, it was observed that partial discharge, partia discharge initial voltage and puncture voltage were affected by insulating thickness, type of insulator, type of electrode, test method.