Figure P315 Shows a One-Line Diagram of a System in Which

Essay

Figure P3.15 shows a one-line diagram of a system in which the three-phase generator is rated 300 MVA, $20 \mathrm{kV}$ with a subtransient reactance of 0.2 per unit and with its neutral grounded through a $0.4-\Omega$ reactor. The transmission line is $64 \mathrm{~km}$ long with a series reactance of $0.5 \Omega / \mathrm{km}$ . The three-phase transformer $T_{1}$ is rated $350 \mathrm{MVA}, 230 /$ $20 \mathrm{kV}$ with a leakage reactance of 0.1 per unit. Transformer $T_{2}$ is composed of three single-phase transformers, each rated $100 \mathrm{MVA}, 127 / 13.2 \mathrm{kV}$ with a leakage reactance of 0.1 per unit. Two $13.2-\mathrm{kV}$ motors $M_{1}$ and $M_{2}$ with a subtransient reactance of 0.2 per unit for each motor represent the load. $M_{1}$ has a rated input of 200 MVA with its neutral grounded through a $0.4-\Omega$ current-limiting reactor. $M_{2}$ has a rated input of 100 MVA with its neutral not connected to ground. Neglect phase shifts associated with the transformers. Choose the generator rating as base in the generator circuit and draw the positive-sequence reactance diagram showing all reactances in per unit.

Figure P3.15