Power Transformer

Learn about power transformers — construction, working, testing, protection, and maintenance for efficient voltage transformation in power systems.

Restricted Earth Fault (REF) Protection of Transformer

by

Restricted Earth Fault (REF) protection is a special type of protection. This protection scheme is mainly applied to power transformers. This scheme is designed to detect only the internal earth faults of the transformer. It provides highly sensitive and selective protection for internal earth faults. Restricted earth fault protection is a unit protection scheme. REF … Read more

High Impedance REF Protection of Transformer- Complete Guide

by

There is a disadvantage in a low-impedance restricted earth fault scheme. Suppose, due to any fault, any of the line CTs comes under saturation. A spill current starts flowing through the earth fault relay. As a result, the relay may initiate mal-tripping to the transformer circuit breakers. Although the fault is not related to the … Read more

Backup Protection of Transformer – Over Current Earth Fault

by

A simple overcurrent (O/C) and earth fault (E/F) protection is essential for a power transformer. The O/C protection operates whenever the phase current exceeds a preset value. E/F protection responds to residual or zero-sequence current. Overcurrent and earth fault protection of power transformers uses simple IDMT or DMT relays. It cannot distinguish between internal and … Read more