Transient-based protection responds to short-lived features in the relay input currents and voltages. Fault transients are not powered by the sources present in the system but by the energy stored in the system components prior to the fault: transmission lines, capacitor banks . 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 continue to run under normal conditions. Types of Protective Relays: Protective relays are categorized by their mechanism (electromagnetic, static, mechanical) and function. We have three ways to tackle the rising protection challenges: fine-tune the present protective relays, enforce a better fault response of the sources, and use protection principles that are less dependent on the sources. : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as.
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