Statement for Linked Answer Questions 52 and 53: Two generator units $G_1$ and $G_2$ are connected by a 15 kV line with a bus at the midpoint, as shown below. $G_1 = 250$ MVA, 15 kV, positive-sequence reactance $X = 25\%$ on its own base $G_2 = 100$ MVA, 15 kV, positive-sequence reactance

Question

Statement for Linked Answer Questions 52 and 53: Two generator units $G_1$ and $G_2$ are connected by a 15 kV line with a bus at the midpoint, as shown below. $G_1 = 250$ MVA, 15 kV, positive-sequence reactance $X = 25\%$ on its own base $G_2 = 100$ MVA, 15 kV, positive-sequence reactance $X = 10\%$ on its own base $L_1$ and $L_2 = 10$ km, positive-sequence reactance $X = 0.225\ \Omega$/km For the above system, the positive-sequence diagram with the p.u. values on the 100 MVA common base is

Accepted Answer

(A). To draw the positive-sequence diagram on a 100 MVA base, each generator reactance is converted from its own base to the common base, and the line reactances are converted from ohms to per unit using the 15 kV base. The resulting per-unit values match diagram (A).

Solution

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