A Look Back at History

James R. White, Shermco IndustriesColumns, Fall 2021 Columns, Tech Quiz

1. Describe the function of polarity marks on current transformers.

2. Transformer differential relays protecting a 50 MVA, 138 kV – 13.09 Y/7.56 kV transformer have been operating normally during the construction phase of a project. When the transformer is being brought up to full load it trips. There is no indication of a fault, as all tests on the transformer and cable are acceptable. What are the most likely causes?

3. What is the definition of a CT accuracy class (i.e. Class C200)?

4. Relay CTs are available in either Class C or Class T. What is the difference?

Jim White wrote his first Tech Quiz in the Fall 2002 issue of NETA World. He would go on to write 75 consecutive Tech Quiz columns over the next 19 years of his service to NETA and the industry. Nationally recognized for technical skills and safety training in the electrical power systems industry, Jim never turned down a request from NETA World staff for support or guidance. He will be missed.



James (Jim) R. White, Vice President of Training Services, had worked for Shermco Industries Inc. since 2001. He was a NFPA Certified Electrical Safety Compliance Professional and a NETA Level 4 Senior Technician. Jim was NETA’s principal member on NFPA Technical Committee NFPA 70E®, Electrical Safety in the Workplace®; NETA’s principal representative on National Electrical Code® Code-Making Panel (CMP) 13; and represented NETA on ASTM International Technical Committee F18, Electrical Protective Equipment for Workers. Jim was Shermco Industries’ principal member on NFPA Technical Committee for NFPA 70B, Recommended Practice for Electrical Equipment Maintenance and represented AWEA on the ANSI/ISEA Standard 203 Secondary Single-Use Flame Resistant Protective Clothing for Use Over Primary Flame Resistant Protective Clothing. An IEEE Senior Member, Jim received the IEEE/IAS/PCIC Electrical Safety Excellence Award in 2011 and NETA’s Outstanding Achievement Award in 2013. Jim was Chairman of the IEEE Electrical Safety Workshop in 2008 and was Vice-Chair of the IEEE IAS/PCIC Safety Subcommittee.