Impedance diagram, 100 MVA 132 kV base, with load

Base values

• $S_b = 100$ MVA, and $V_b = 132$ kV in the transmission circuit, so $Z_b = 132^2/100 = 174.24\ \Omega$.
• G1 side, through T1 (12.2/161 kV): $V_b = 132\times\dfrac{12.2}{161} = 10.0025$ kV.
• G2 side, through T2 (161/13.8 kV): $V_b = 132\times\dfrac{13.8}{161} = 11.3143$ kV.

Per-unit impedances

Use $Z_{new} = Z_{old}\dfrac{S_b}{S_{rated}}\left(\dfrac{V_{rated}}{V_b}\right)^2$.

$$\begin{aligned} G_1&: 0.15\times\frac{100}{50}\left(\frac{13.8}{10.0025}\right)^2 = j0.5710\\ T_1&: 0.1\times\frac{100}{80}\left(\frac{161}{132}\right)^2 = j0.1860\\ T_2&: 0.1\times\frac{100}{40}\left(\frac{161}{132}\right)^2 = j0.3719\\ G_2&: 0.15\times\frac{100}{20}\left(\frac{13.8}{11.3143}\right)^2 = j1.1157 \end{aligned}$$

Lines:

$$\begin{aligned} Z_{40+j160} &= \frac{40 + j160}{174.24} = 0.2296 + j0.9183\\ Z_{20+j80} &= \frac{20 + j80}{174.24} = 0.1148 + j0.4591\ \text{(each section)} \end{aligned}$$

Load (50 MVA, 0.8 lagging, 154 kV): $V = 154/132 = 1.1667$ p.u. and $S = 0.5$ p.u.

$$Z_L = \frac{|V|^2}{S^*} = \frac{1.1667^2}{0.5}\angle36.87^\circ = 2.7222\angle36.87^\circ = 2.1778 + j1.6333\ \text{p.u.}$$

Impedance diagram

 j0.571  j0.186      0.2296+j0.9183      j0.3719  j1.1157
+-/\/\----/\/\--+-------/\/\/\/\-------+--/\/\----/\/\--+
|               |                      |               |
(E1)            +-0.1148+j0.4591-+-0.1148+j0.4591-+   (E2)
|                                |                     |
|                        2.1778+j1.6333 (load)         |
|                                |                     |
+---------------- reference -----+---------------------+