Practice Test Geeks(SOPD) System Operator/Power Dispatching Practice Test
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Voltage Control & System Reliability 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.

Read the first 7 Voltage Control & System Reliability flashcards as text

  1. What is the significance of the 'nose point' on a P-V curve?

    Answer: It represents the maximum power transfer point beyond which voltage collapse is imminent

    The nose point is the critical maximum loadability limit on a P-V curve; operating beyond it causes voltage collapse.

  2. A transformer's load tap changer (LTC) is set to automatic mode during a system emergency with low voltage. Why might operators place the LTC in manual mode?

    Answer: To prevent LTC operation from masking low voltage conditions and depleting reactive reserves further

    Automatic LTC action during low voltage can mask the true voltage problem and increase reactive demand, worsening reactive reserve depletion.

  3. Which NERC Reliability Standard specifically addresses Transmission Operator requirements for maintaining voltage profiles?

    Answer: VAR-001

    VAR-001 (Voltage and Reactive Control) establishes requirements for Transmission Operators to maintain voltage and reactive control within defined limits.

  4. A shunt reactor is connected to a 500 kV bus during light load conditions. What is its primary function?

    Answer: To absorb reactive power and prevent overvoltage due to line charging

    Shunt reactors absorb reactive power (consume VARs), counteracting the capacitive charging of lightly loaded long transmission lines that would otherwise cause overvoltage.

  5. During a post-contingency analysis, an N-1 contingency is found to cause a bus voltage to drop to 0.91 pu. Under NERC TPL standards, this result indicates:

    Answer: A possible violation requiring evaluation against applicable voltage limits and corrective action plans

    A post-contingency voltage of 0.91 pu may violate planning or operating voltage limits, requiring evaluation and a corrective action plan per NERC TPL standards.

  6. What is the effect of increasing the X/R ratio of a transmission line on voltage stability?

    Answer: Higher X/R ratios (more reactive) increase the sensitivity of voltage to reactive power changes, making voltage stability more challenging

    Transmission lines with high X/R ratios have voltage profiles that are highly sensitive to reactive power changes, making voltage stability more difficult to maintain.

  7. A STATCOM differs from a conventional SVC primarily because it:

    Answer: Uses voltage-source converter technology and can supply full reactive current even at very low voltages

    A STATCOM uses voltage-source converter (VSC) technology and maintains full reactive current output even at depressed voltages, unlike an SVC whose output is proportional to voltage squared.