Protective Relaying

James R. White, Shermco IndustriesColumns, Tech Quiz, Winter 2020 Columns

This edition of Tech Quiz covers protective relays. Many years ago, as I was teaching a protective relay class, a student asked, “What are these things?” I replied, “Relays,” to which he answered, “No, relays are those little black plastic things that go click-click.” I made sure to call them protective relays from then on. Things in the protective relaying field have progressed rapidly over the years, and digital protective relays are now the norm as is digital test equipment.

1. One question always seen on the NETA exams is about protective relay ANSI numbering. What is the protective relay number for a synchronizing relay?

a. 25

b. 32

c. 52

d. 86

2. Which protective relay looks inside a generator?

a. Distance relaying

b. Mho relays

c. Ohm relays

d. Loss-of-excitation relays

3. What does Figure 1 illustrate?

a. Mho relay characteristic

b. Ohm relay characteristic

c. Reactance relay characteristic

d. Offset relay characteristic

Figure 1: Which Relay?

4. Looking at the internal schematic in Figure 2, identify the following components:

a. _____________________________


b. _____________________________


c. _____________________________


d. _____________________________


Figure 2: Internal Schematic



James (Jim) R. White, Vice President of Training Services, has worked for Shermco Industries Inc. since 2001. He is a NFPA Certified Electrical Safety Compliance Professional and a NETA Level 4 Senior Technician. Jim is 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 represents NETA on ASTM International Technical Committee F18, Electrical Protective Equipment for Workers. Jim is Shermco Industries’ principal member on NFPA Technical Committee for NFPA 70B, Recommended Practice for Electrical Equipment Maintenance and represents 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 is currently Vice-Chair for the IEEE IAS/PCIC Safety Subcommittee.