Unbalanced control strategy can ensure the safety of static synchronous compensator (STATCOM) when the network three-phase voltage is unbalanced, and achieves excellent effect of voltage control. For the non-uniform parallel transmission lines with single path shunt-compensated by STATCOM, operation condition of the impedance relays with short-circuit fault on the line is analyzed. It is confirmed that STATCOM under unbalanced control strategy may cause fault phase under-reaching and non-fault phase over-reaching. Considering current injection from STATCOM, modified fault location method is proposed. The measuring impedance of distance protection is corrected through coordinating the fault distance with the positive impedance of the line. Simulation results show that the modified algorithm guarantees correct operation of impedance relays, avoiding re-tuning distance protection after joining in STATCOM.