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Switching Transients, Transformer Failures and Practical Solutions

Date: Thursday, June 23rd, 2016

Location: SRP Information Services Building (ISB), 1600 N Priest Dr, Tempe, AZ 85281

Speaker: Thomas Dionise, Eaton Electrical Inc.

Topic: "Switching Transients, Transformer Failures and Practical Solutions"

Switching transients associated with circuit breakers have been observed for many years. Recently this phenomenon has been attributed to a significant number of power transformer failures involving primary circuit breaker switching. This presentation will review these recent transformer failures due to primary circuit breaker switching transients to show the severity of damage caused by the voltage surge and discuss the common contributing factors. Case studies will illustrate how breaker characteristics of current chopping, re-strike/re-ignition and pre-strike combine with critical circuit characteristics to cause transformer winding failure. This presentation will also address two special types of medium voltage transformer failures: 1) potential transformer (PT) failures due to ferroresonance, and 2) reduced voltage auto-transformer (RVAT) failures due to internal resonance. For these various medium voltage switching transient induced transformer failures, the presentation will provide means of prediction, measurement and practical solution. Finally, several techniques and equipment that have proven to successfully mitigate the breaker switching transients will be presented including surge arresters, surge capacitors, snubbers, damping resistors and these in combination.

Speaker Bio:
Thomas J. Dionise, PE, (IEEE S ’79, M ’82, SM ’87) is a Power Quality Advisory Engineer with Eaton Corporation in the Power System Engineering Department. He has 33 years of power system experience involving analytical studies and power quality investigations of industrial and commercial power systems. In the metals industry, he has specialized in power quality investigations, harmonic analysis and harmonic filter design for electric arc furnaces, rectifiers and VFD applications. He is an instructor for Eaton’s Power Quality Monitoring Class and Harmonic Analysis Class. He is a Senior Member of the IEEE, Chair of the Metal Industry Committee, and member of the Generator Grounding Working Group. He has co-authored 30 technical papers on various power quality topics, including a paper on harmonic filter design for an electric arc furnace that received the 2011 IEEE Transactions on Industry Applications 2nd Prize Paper Award. Tom has served in local IEEE positions, and had an active role in the committee that planned the IAS 2002 Annual Meeting in Pittsburgh, PA. He is a licensed Professional Engineer in PA, and received a MSEE from Carnegie Mellon University in 1984 and a BSEE from Pennsylvania State University 1982.