Key types include Overcurrent Relays for detecting excessive currents, Differential Relays for internal fault protection, and Distance Relays for transmission line protection. Voltage and Frequency Relays monitor abnormal voltage or frequency levels. Protective Relay Definition: A protective relay is an automatic device that senses abnormal conditions in electrical circuits and triggers actions to isolate faults. Product Specialist (West Region) for Digital Substation Products at ABB Inc. Currently residing in Denver, Colorado. Its main purpose is to safeguard electrical equipment like transformers, generators, and transmission lines from damage due to. An electrically operated switch like a relay plays a key role in controlling an electrical circuit through an independent low-power signal, otherwise used where a number of circuits should be controlled through the single signal. When a fault occurs, milliseconds matter.
[PDF Version]