Free sample: 2 of 45
Answer each one 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.
A large shunt capacitor bank at a 230 kV station has a small reactor in series with each phase of the bank. What does that reactor do?
- A. It limits inrush current when the bank is energized
- B. It raises the bank's output when bus voltage is low
- C. It holds the bank's neutral at ground potential
- D. It drains the trapped charge after the bank is removed
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Answer A It limits inrush current when the bank is energized
The series reactor adds just enough inductance to hold the energization inrush and its frequency within what the switching device and the capacitor units can take, which matters most when one bank is closed alongside another already in service. Bleeding off trapped charge is the job of the bank's discharge device.
Reference: Power system fundamentals
An operator raises the power order on a line-commutated high voltage direct current (HVDC) tie from 400 MW to 700 MW. What should be expected on the alternating-current (AC) systems at the two converter stations?
- A. Both converters supply Reactive Power, lifting AC voltage
- B. Both converters absorb more Reactive Power, depressing AC voltage
- C. The rectifier absorbs Reactive Power while the inverter supplies it
- D. Reactive Power at each station is unaffected by the power order
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Answer B Both converters absorb more Reactive Power, depressing AC voltage
A line-commutated converter draws reactive power roughly in proportion to the direct power it handles, and it does so at both the rectifier and the inverter, so a higher power order deepens the MVAr demand at each end. Filters and capacitor banks are switched in to hold the AC voltage as the order is raised.
Reference: Power system fundamentals
