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Explore electrical protection systems — relays, breakers, and fault detection schemes ensuring safety and reliability in power networks.
The transformer differential protection belongs to the unit protection scheme. A unit protection confines itself within a defined zone. A differential protection scheme compares the vector sum of currents entering and leaving the protected equipment. In other words, it uses Kirchhoff’s current law. Under healthy and external fault conditions, the currents entering and exiting the … Read more
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
Before entering the topic of line differential protection, or simply differential protection of a transmission line, we shall first recall our concept of differential protection. Actually, the differential protection used for a transmission line is called line differential protection. We have already heard about the differential protection of transformers, busbars, etc. The same principle is … Read more
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
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
We are going to discuss here in this article a clear idea about SOTF Protection. Sometimes it becomes necessary to open a circuit breaker just after closing. This is due to the presence of a fault during the closing of the circuit breaker. This type of condition may arise due to different reasons. Such as … Read more