Protective Relays

Virginia Balitski, Magna IV EngineeringColumns, Spring 2024 Columns, Tech Quiz

Protective relays are critical power systems components, and it is essential to design and use them properly to detect power system issues. As NETA-certified technicians, we must be familiar with the purpose and operation of various types of protective relays. 

1. Which type of relay was the earliest design for protective relaying?
a. Interconnector relay
b. Electromechanical relay
c. Static relay
d. Microprocessor relay

2. What is the most common type of protection used in power distribution systems?
a. Directional
b. Overvoltage
c. Reverse power
d. Overcurrent 

3. Which ANSI protective element will only operate when current flows in a specific direction?
a. 67 
b. 59
c. 51
d. 24

4. What does MTA stand for when reviewing the settings on a 67 protective relay?
a. Motor torque angle
b. Minimum time allowance
c. Maximum torque angle 
d. Mechanical trip adjustment

5. Which power system study ensures that all upstream and downstream protective devices operate in the proper sequence?
a. Coordination study
b. Short circuit study 
c. Arc flash study 
d. Load flow study

6. Which protective relay function can be utilized to lower the predicted incident energy of an arc flash event?
a. Remote operation 
b. Energy-reducing maintenance switching 
c. Finger-safe components 
d. Phase sequence protection 

7. Which relay protective element would typically incorporate a minimum voltage setting and a time delay to prevent nuisance tripping?
a. Phase sequence 
b. Directional 
c. Undervoltage 
d. Distance 

8. Protective relays are important on power systems for which of the following reasons?
a. Safety of a system
b. Prevent equipment damage 
c. Selectivity of a system
d. All of the above  

Virginia Balitski, CET, Manager – Training and Development, has worked for Magna IV Engineering since 2006. Virginia started her career as a Field Service Technologist and achieved NETA Level 4 Senior Technician certification. She is also a Certified Engineering Technologist through ASET – The Association of Science & Engineering Technology Professionals of Alberta. Virginia has since dedicated her time to the advancement of training and safety in the electrical industry. She is the current vice-chair of the CSA Z462, Workplace Electrical Safety Committee; is a member of the NFPA 70E, Electrical Safety in the Workplace Technical Committee; and represents NETA on the ASTM F18 Committee. Virginia serves on NETA’s Board of Directors and is involved with many NETA committees.