Practice Test Geeks(SOPD) System Operator/Power Dispatching Practice Test
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Frequency Control Flashcards

7 cards from real SOPD practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is 'inertia' in the context of power system frequency control?

    Answer: The kinetic energy stored in rotating generator masses that initially resists frequency change

    System inertia is the kinetic energy stored in spinning generator rotors that temporarily resists frequency change following a generation-load imbalance.

  2. Under-frequency load shedding (UFLS) programs are designed to activate at what general frequency threshold in North American systems?

    Answer: 58.5–59.5 Hz depending on scheme design

    UFLS schemes typically have multiple stages activating between approximately 58.5 Hz and 59.5 Hz, with exact thresholds varying by utility and regional criteria.

  3. A system operator is monitoring a declining frequency event. The Rate of Change of Frequency (ROCOF) is -1.2 Hz/s. What does this indicate?

    Answer: The system has low inertia and is experiencing a severe generation deficit

    A high ROCOF magnitude such as -1.2 Hz/s indicates low system inertia and a significant generation-load imbalance requiring immediate response.

  4. What is 'secondary frequency control' in power system operations?

    Answer: AGC action that restores frequency to scheduled value and resets tie-line flows after primary response

    Secondary frequency control (AGC) acts over minutes to restore frequency to exactly 60 Hz and return tie-line flows to scheduled values after primary response arrests the deviation.

  5. Which factor does NOT directly reduce available primary frequency response in an interconnection?

    Answer: High ambient temperature reducing transformer efficiency

    Transformer efficiency affected by ambient temperature does not directly reduce primary frequency response capability, which depends on generator headroom, governor status, and synchronous inertia.

  6. In the ACE formula, what does a negative ACE value indicate for a balancing authority?

    Answer: The control area is generating less than its scheduled net interchange plus frequency obligation

    Negative ACE means the area is under-generating relative to its schedule and frequency obligation, requiring AGC to increase generation.

  7. What is the significance of the 'settling frequency' after a large generation trip?

    Answer: It is the steady-state frequency after governor response but before AGC fully restores 60 Hz

    Settling frequency is the quasi-steady-state value after primary (governor) response arrests the decline but before secondary (AGC) response restores 60 Hz.