Reducing Arc Flash Incident Energies on the Transformer Secondary With MV Fuse Based Protection


Traditional electrical system design approaches and transformer fuse protection practices have yielded arc flash incident energy calculations well above 40 cal/cm2 on the secondary of many power transformers. Many companies use this value as the upper limit for energized work. Consequently these companies insist on outages to perform routine tasks on this equipment. When the equipment is switchgear feeding large processes, the downtime cost of a task such as racking in and closing a power circuit breaker can be tens of thousands of dollars.

This session presents two potential solutions that overcome the shortcomings of traditional primary fuse protection against secondary arc flash events while maintaining all the advantages of primary current limiting fuse protection. The performance tradeoffs of each approach are covered. With the approaches that use overcurrent relays, incident energy calculations are typically reduced to PPE Category 2 or ‘0’. 

Topics include:

  •  • Transformer Protection Overview 
  • • Protection Issues for Secondary Faults • Protection Considerations for Transformer Primary Faults
  •  • Fuse Selection Criteria • Introduction to Two Approaches to Reduce Incident Energy
  •  • Changing the time current characteristics of the MV fuse 
  • • MV High Speed Grounding Switch 
  • • Retrofit Considerations 
  • • Modeling Discussion


Mike Lang, Principal Field Engineer for Mersen, has participated in over1,000 arc flash tests in Mersen’s high power test lab as leader of theMersen arc flash team. He has coauthored several prize-winning IEEEpapers on arc flash including papers at the 2006 PCIC Conference, the2008 PPIC Conference and 2016 PPIC Conference. He was also awardedthe 2011 I&CPS Ralph H. Lee Department Prize Paper Award for his workon 208V arc flash research. He recently received the 2018 Technical Awardfor Excellence in Prevention Through Design by the Electrical SafetyCommittee of the IEEE Industrial Application Society. 

Mike is currently co-chairman of the IEEE/NFPA Collaboration on ArcFlash Research effort and has served as a member of the Research, Testand Planning Committee and on the Technical Advisory Committee as partof Mersen’s Platinum sponsorship of the Collaborations research. Mike isan active member of the IEEE 1584 Working Group.

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This is a seminar runs from 11:00am to 12:00pm EDT

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