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Answer it before you open the explanation. On the exam there's no explanation, and you have about 77 seconds a question on RC and BT, 90 on TO and BI.
Eastern Interconnection frequency settles at 59.6 Hz for two minutes after a large generation loss. Under NERC Reliability Standard PRC-024-3 Attachment 1, applicable frequency protection must
- A. trip the resource once the excursion has lasted more than 180 seconds
- B. let the resource keep operating, since 59.6 Hz is above 59.5 Hz
- C. trip the resource instantaneously, as 59.6 Hz is below 60.0 Hz
- D. allow ten seconds of operation and then trip the resource
Show the answer
Answer B let the resource keep operating, since 59.6 Hz is above 59.5 Hz
Table 1 of Attachment 1 places the Eastern Interconnection continuous-operation boundary above 59.5 Hz, so at 59.6 Hz the protection must not trip the resource, no matter how long the excursion lasts. The 180-second figure comes from the Western Interconnection table, at 59.4 Hz and below.
Reference: PRC-024-3 R1 and Attachment 1, Table 1
