Definition
The real-time performance signal that indicates how well a Balancing Authority (BA) is meeting its obligation to balance load and generation within its area. ACE is calculated as: ACE = (NIA − NIS) − 10B × (f − f₀), where NIA is actual net interchange, NIS is scheduled net interchange, B is the frequency bias setting (MW/0.1 Hz), f is actual system frequency, and f₀ is scheduled frequency (60 Hz). A positive ACE indicates the BA is exporting more than scheduled (over-generating), while a negative ACE indicates under-generation. NERC reliability standards (BAL-001, BAL-002) require BAs to minimize ACE and return it to zero within defined time limits. Automatic Generation Control (AGC) continuously adjusts generator output to drive ACE toward zero on a second-by-second basis.
Topic Deck
Grid Operations
Source
FERC Pro Forma OATT / LGIP
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