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Tutorials
4th International Colloquium "Transformer Research and Asset Management"
Pula / Croatia
May 10 - 12, 2017
Antun Mikulecky
Transformer Bushing Reliability
| Transformer bushings reliability tutorial is based on work done by CIGRE WG A2.43 and covers bushings with system voltage above and including 72,5 kV. Tutorial covers the history of bushing development as well as the description and role of resin bonded paper, oil impregnated paper and resin impregnated paper bushing. The results of 4 international surveys about bushing failures, reliability and diagnostics will be presented. Failure modes and typical bushing failures will also be presented. Bushing on-line (continuous) and off-line (periodic) diagnostics together with decision criteria will be discussed. Tutorial will conclude with bushing storage recommendation. |
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Antun Mikulecky has 37 years of power transformers research and development experience. His field of expertize are research and development of insulating systems of HV and HVDC transformers, diagnostic, maintenance and failure analysis of power transformers including ageing and life expectance and their bushings in particular. He is Convener of the CIGRÉ WG A2.43: Transformer bushings reliability and lecturer on Postgraduate Specialist Study – Transformers, University of Zagreb. He has written more than 100 research reports, various studies and technical instructions, made at request of manufacturers and buyers of transformers and 50 published papers in the fields of expertize. |
Raka Levi
Dynamic Testing for On Load Tap Changer Condition Assessment
| The AMforum association, an independent asset managers’ forum of TSO operators in Europe formed a working group in 2010 to investigate and standardize the DRM (dynamic resistance measurement) for OLTC condition assessment. Producers of tap changers, manufacturers of test instruments, and utility and service companies using this method collected their experience into a significant knowledge-base. The tutorial will start with different tap changer constructions and principles of operation. Further we will explain procedure of the dynamic measurements for resistor and reactor types of tap changers, and a resulting graph analysis. Advantages and disadvantages of different methods and connections will be presented. Several interesting cases from the knowledge base will be shown demonstrating diagnostic power of the test-current and motor-current graph analysis. |
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Raka Levi has 30 years of asset performance and condition assessment experience, specializing in apparatus testing, monitoring and diagnostics. During his career, Dr. Levi has provided consulting service to utility clients in Europe and USA in the field of diagnostic testing, and investigations as a part of comprehensive substation condition assessment programs. Six years ago he started within the AMforum organization a working group on DRM test methodology for tap changers. For 20 years he has been running committees that assemble asset managers and operations specialists of major European utilities, organizing AMforum conferences in Europe, Tap Changer Universities in USA, and Tap Changer Colleges in Asia. |
