Problem 1. (35 points) Assume a three-phase, unity (1.0) power factor load of $100 \mathrm{MVA}$ with line-to-line voltage of $69 \mathrm{kV}$ is connected to a source through the below network. Convert the two impedances $Z_{1}$ and $Z_{2}$ to per unit, and then determine the per unit generator voltage $\overrightarrow{V_{1}}$ (magnitude and angle). Use a per unit three-phase $100 \mathrm{MVA}$ base, a line-to-line $138 \mathrm{kV}$ voltage base on the left side of the transformer and a line-to-line $69 \mathrm{kV}$ voltage base on the right side. The three-phase transformer is $Y / Y$-connected, and the transformer is an ideal transformer. The source and load are both Y-connected.

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