87T relay selection starts with the transformer, not the relay. Fix rated power, voltage ratio, vector group, CT data and the protection functions the scheme must deliver, then match a relay that covers those numbers. Transformer differential relay selection is…

What Is Generator Differential Protection? Generator differential protection 87G is a unit protection scheme: it compares the current measured at the generator terminal CTs with the current measured at the neutral CTs, and it trips only when the difference points…

Bus differential protection is the fastest way to clear an internal busbar fault before it spreads to the whole switchboard. Written by Leon Zhang, Protection Application Engineer · Technical review by Li Ming, Electrical Engineer · Last reviewed September 2026…

At a Glance: Distance Protection for Transmission Lines Hardware for this duty is an ANSI 21 line protection relay that keeps zone reach, characteristic and delay as separate setting groups. IEC 60255-1:2022 sets the general requirements for the relay, and IEEE C37.113-2025…

Pump protection relays are motor protection devices set up for pump duty: they trip on dry running, overload, phase loss, jamming and earth fault before the motor or the mechanical seal is destroyed. The ANSI functions behind those trips are…

Microprocessor based relays are digital protection devices that sample CT and VT secondary quantities, convert them into numbers several times per power cycle, and run the protection logic in software rather than in springs, disks and fixed analogue circuits. One…

Protection relays in power system projects decide which breaker opens, how fast, and how much of the network goes dark. Choosing between a Chinese and an imported relay rarely turns on protection logic: both sides ship numerical relays covering the…