I’m reviewing information for the next book in The Relay Testing Handbook series and came across this Youtube channel.
This is a dated, but excellent, video introduction to overcurrent protection (50/51) relays that has some great information to help you understand protective relays.
The video reviews the basics of overcurrent protection and provides detailed information regarding electro-mechanical relays and their functions.
Introduction to Protective Relays Video
http://youtu.be/owWleWmSYQE
I hope you find it useful!
