View low frequency excursions
The large differential between the number of abnormal frequency events in each interconnection, requires the y-axis scale to be logarithmic. During 2008 there was a reduction of about 25-percent in the number of high frequency events during the on peak period in the Eastern interconnection, and an increase of about 300-percent in the Western Interconnection.
The ability to maintain load-generation balance at all times is a key indicator to measure real power balancing control performance. Prolonged system recovery performance could indicate at-risk operations, decline in frequency response or degradation of regulation and reserve sharing capability. The Frequency Trigger Limits (FTLs) are defined as thresholds. An FTL-Low alarm is generated when interconnection frequency is lower than FTL-Low for 5-minutes or more. The FTL-Low is 59.950 Hz for Eastern Interconnection and 59.856 Hz for Western Interconnection. An FTL-High alarm is generated when interconnection frequency is higher than FTL-High for 5-minutes or more. The FTL-High is set at 60.050 Hz and 60.144 Hz for Eastern and Western Interconnection respectively.
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