System protection and control task force´s initial recommendations concerning NERC recommendation 8A loadability requirements on transmission protective relaying systems

This paper discusses with system protection and control task force´s initial recommendations concerning with NERC recommendation 8A loadability requirements on transmission protective relaying systems. The NERC investigation team recommends that the zone 3 relay, if used, should not operate at or below 150% of the emergency ampere rating of a line, assuming a .85 per unit voltage and a line phase angle of 30 degrees. The planning committee shall review such exceptions to ensure they do not increase the risk of widening a cascading failure of the power system.