Motor startup generates inrush currents typically 5-7 times higher than FLA. Some standards permit temporarily increasing relay settings to 140% of FLA during startup to prevent nuisance tripping. For example, unselective protection operation during a medium voltage network fault will cause an outage for an unnecessarily large number of consumers. While this is bad, It's not a. Protective Relays - Technical Seminar Nov 2016 - Copyright: IEEE 2 Abstract: Protective relays and devices have been developed over 100 years ago to provide “lastline”of defense for the electrical systems. They are intended to quickly identify a fault and isolate it so the balance of the system. The SEL-751 is the right solution for industrial and utility feeder protection, with conventional/low-energy analog (LEA) current and voltage input support, flexible I/O options, easy mounting, and fast settings. The SEL-751 provides complete protection for radial and looped distribution circuits. This document supplements PJM Manual 07 which contains the minimum design standards and requirements for the protection systems associated with the bulk power facilities within PJM. Also principles of various protective relays and schemes including special protection.
