An electric power system includes generators, power transformers, transmission lines, switchgear, distribution circuits, and residential and business customer equipment. At any time, severe weather, accidents, or other factors may cause part of the system to fail. If the system is not properly protected, a failure can result in personal injuries and extensive equipment damage. One of the keys to protecting equipment and personnel from failures is the use protective relays.
This program focuses primarily on relays that are used in transmission systems. Distribution system relays are covered in Relays unit 1.
SUBJECTS AND OBJECTIVES
Introduction to Relays
- Identify five common relay elements
- Identify the functions of overcurrent, directional overcurrent, reclosing, voltage, and auxiliary relays.
- Identify what differential relays typically protect.
- Describe the condition that causes a differential relay to operate.
- Describe the basic operating principles of differential relays.
- Describe the function of transfer tripping.
- Identify the main components of a transfer tripping system.
- Identify four communication channels used for transfer tripping and explain how they work.
- Identify the main equipment associated with transfer tripping communication channels and describe the function of each type of equipment.
- Identify what distance relays typically protect.
- Describe the condition that causes a distance relay to operate
- Describe the basic operating principles of distance relays.
Pilot Wire Relaying
- Describe the function of a pilot wire relaying system.
- Identify the main components of a pilot wire relaying system.
- Describe the basic operating principles of a pilot wire relaying system.
Breaker Failure Relaying
- Identify the function and the main components of a breaker failure relaying systems.
- Describe the general operation of a breaker failure relaying system.
- Describe the basic operating principles of a breaker failure relay.
- Describe the basic operating principles of a timing relay in a breaker failure relaying system.