Protection relays detect faults by comparing the quantity (and angles in some cases) of the primary circuit current or voltage to a pre-determined setting. This comparison is done electromechanically for induction-type relays and digitally or electronically for digital or static. The main relay protection functions (overcurrent, directional, differential, distance, etc. ) and network communication systems (SCADA, RTUs, digital and analog inputs and outputs, IEC 61850, etc. ) are briefly explained in this technical article. Directional distance and overcurrent schemes, interfaced with communication equipment, send and receive logic-based information between relay te minals to determine if the fault is external or internal to the. Relion protection and control relays for several application reduce complexity. Its main purpose is to safeguard electrical equipment like transformers, generators, and transmission lines from damage due to. Protective relays and devices have been developed over 100 years ago to provide “lastline”of defense for the electrical systems.
[PDF Version]