STEP $1$: Divide the power system into different regions based upon the voltage levels. Region $1$: Generator$$s terminal and the primary of the transformer T$1$ Region $2$: Secondary of the transformer $1,$ the transmission line, and the primary of the transformer T$2$ Region $3$: Secondary of the transformer T$2$ and the load STEP $2$: Compute the total impedance that appears at the generator$$s terminals starting from the load $($Region $3)$ and moving towards Region $1$ as follows: Load impedance Zload $=$ Turn ratio of T$2=$ aT$2=$ Load impedance Zload referred to the primary of T$2=$ ZL$,$T$2$