Introduction to Relays – 8 minutes
Explains the purpose of protective relays in a T&D system. Describes five common relay elements and explains how each works.
Overcurrent Relays – 11 minutes
Describes the condition that causes an overcurrent relay to operate. Describes the basic operating principles of overcurrent relays.
Directional Overcurrent Relays – 11 minutes
Identifies T&D equipment typically protected by directional overcurrent relays. Describes the basic operating principles of directional overcurrent relays and the conditions that cause them to operate.
Reclosing Relays – 7 minutes
Describes the function and basic operating principles of reclosing relays.
Voltage Relays – 5 minutes
Identifies the type of equipment that voltage relays typically protect. Describes the basic operating principles of voltage relays, and the conditions that cause them to operate.
Auxiliary Relays – 5 minutes
Describes the basic functions and operating principles of auxiliary relays.
Solid-State Relays – 7 minutes
Describes the basic operating principles of solid-state relays. Defines these terms: analog signal, digital signal, and logic circuit.