This study investigates the relationship between power transfer and transmission losses in a transmission system incorporating a Thyristor-Controlled Phase-Shifting Transformer (TCPST). A balanced two-bus transmission system with a constant power-factor load is first analysed in MATLAB to retain the original study’s-controlled baseline result. The study is then extended using the standard IEEE 14-bus benchmark to examine the network-level sensitivity of a TCPST installed on the 4-5 corridor. The benchmark extension evaluates TCPST phase shifts from −20° to +20°, load scaling, transmission-line parameter sensitivity, and steady-state comparative screening with TCSC, SVC and a UPFC-equivalent model. The original two-bus results show that higher power transfer increases line current and transmission losses while efficiency decreases, with little sensitivity to the tested TCPST phase range. In contrast, the IEEE 14-bus screening study shows that phase shifting can substantially redistribute active power among parallel paths and can increase total losses when the phase shift is not coordinated with the network operating condition. The benchmark base loss calculated from the published IEEE 14-bus operating point is 13.386 MW, compared with 13.393 MW reported for the MATPOWER benchmark case. The combined results demonstrate that TCPST effectiveness is strongly dependent on network topology, operating condition and controller setting, while also providing a reproducible basis for further full AC and converter-level validation.