Relays 1

COURSE DESCRIPTION

When a fault occurs in a transmission and distribution (T&D) system, current increases and voltage decreases.  The increased current causes excessive heating, which, depending on where the fault occurs, can result in a fire or an explosion.  If the fault is not quickly isolated, it can damage that may result in loss of service.

T&D systems use various types of control systems to detect and isolate faults with minimum disturbance.  A key component of all of these control systems is the protective relay.

COURSE GOAL

• This training program examines the functions and operation of some types of protective relays that are commonly found in substations and switchyards.

SUBJECTS AND OBJECTIVES

Introduction to Relays

• Explain the purpose of protective relays in a T&D system.

• Describe how a protective relay is used in a T&D system.

• Describe five common relay elements and explain how they work

Overcurrent Relays

• Describe the condition that causes an overcurrent relay to operate.

• Describe the basic operating principles of overcurrent relays.

Directional Overcurrent Relays

• Identify T&D equipment typically protected by directional overcurrent relays.

• Describe the condition that causes a directional overcurrent relay to operate.

• Describe the basic operating principles of directional overcurrent relays.

Reclosing Relays

• Describe the function of reclosing relays.

• Describe the basic operating principles of reclosing relays.

Voltage Relays

• Identify the type of equipment that voltage relays typically protect.

• Describe the conditions that cause voltage relays to operate.

• Describe the basic operating principles of voltage relays.

Auxiliary Relays

• Describe the basic function of auxiliary relays.

• Describe the basic operating principles of auxiliary relays.

Solid State Relays

• Describe the basic operating principles of solid-state relays.