Standards for Relay Protection of Large Generators
While IEC 60255-1 and IEC 60255-26 are still under revision, the new IEC 60255-181 Standard for Frequency and ROCOF protection functions was published in February 2019. Protective relays and devices have been developed over 100 years ago to provide "last line" 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. Phase Fault Protection 87 – Phase Differential Current 50 – Instantaneous Phase Overcurrent 50DT – Definite Time Overcurrent Ground Fault Protection ( High-Impedance Grounded Gens) 59N – Neutral Overvoltage with accelerated schemes 27TN – Third Harmonic Neutral Undervoltage 59D – Third Harmonic. Two prominent organizations that develop standards for generator protection are the Institute of Electrical and Electronics Engineers (IEEE) and the International Electrotechnical Commission (IEC).
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