Free sample: 2 of 36
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 Transmission Operator is directed to shed 300 MW of firm Load using rotating blocks that each carry about 75 MW. How many blocks must be open at any one moment?
- A. Four blocks
- B. Three blocks
- C. Five blocks
- D. Six blocks
Show the answer
Answer A Four blocks
300 divided by 75 is four, so four blocks have to be open at every instant to hold the 300 MW reduction. Rotation changes which four are open; it does not change how many.
Reference: Control-room operating practice
A Transmission Operator must keep 300 MW of firm Load off for several hours during a Capacity Emergency. Why does its plan rotate which distribution blocks are open rather than leaving the same ones open throughout?
- A. The total Load shed falls as the rotation works through the blocks
- B. No customer group is left without supply for the whole period
- C. Each block's underfrequency relays are re-armed as it is restored
- D. Rotating keeps the shed circuits clear of designated critical loads
Show the answer
Answer B No customer group is left without supply for the whole period
Rotation is about spreading the outage, not reducing it: the same number of blocks stays open at every instant, so the megawatts held off do not change, but no one group of customers carries the whole outage. Keeping critical loads off the shed list is done when the circuits are selected, not by rotating them.
Reference: Control-room operating practice
