GATE EE 2023 Set 1 — Question 21
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Power Systems → Economic Operation & Compensation → Economic Load Dispatch
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Question
The expressions of fuel cost of two thermal generating units as a function of the respective power generation and are given as
Rs/hour
Rs/hour
where is a constant. For a given value of , optimal dispatch requires the total load of 290 MW to be shared as and . With the load remaining unchanged, the value of is increased by 10% and optimal dispatch is carried out. The changes in and the total cost of generation, in Rs/hour will be as follows
Rs/hour
Rs/hour
where is a constant. For a given value of , optimal dispatch requires the total load of 290 MW to be shared as and . With the load remaining unchanged, the value of is increased by 10% and optimal dispatch is carried out. The changes in and the total cost of generation, in Rs/hour will be as follows
Correct answer
(A) P_(G1) will decrease and F will increase
Solution
For optimal dispatch (no losses), the incremental costs of the two units must be equal and the total generation must meet the load.Incremental costsFinding from the given dispatch ( MW, MW, total MW):New dispatch with and :Both units stay within their limits ( MW). Since , decreases: unit 1 has become costlier at the margin, so load shifts to unit 2.Total costInitial:New:This is expected: increasing raises the cost of every possible dispatch of the same 290 MW, so even the new optimum costs more than the old one. Hence increases.Answer: (A) will decrease and will increase
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