In this paper a 25MVA Static Synchronous Compensation Device (STATCOM) that is considered an operative equip-ment for Flexible AC Transmission Systems (FACTS) is aimed at enhancing voltage reliability at a (66 KV, 525MVA) electrical power transmission system. The STATCOM used in this work can regulate the power system's voltage for fluctuations of ±7% from the nominal value. A model of the transmission network in Middle Egypt Electricity Zone has been developed using the Matlab/Simulink platform as well as STATCOM scheme that used to improve the stabil-ity of the system's voltage. The study assesses the electrical grid performance augmented by STATCOM connected in shunt with bus B11 at normal operation and under various faults conditions, including single-phase and three-phase faults. The STATCOM control is accomplished by employing PI controller and Fuzzy Logic Control System (FLC). The study aims to illustrate the effectiveness of FLC over PI controller for preserving the voltage profile at different conditions using STATCOM device. The findings indicate that the proposed system showcases improved voltage per-formance when utilizing the STATCOM device, in both normal and abnormal circumstances, compared to scenarios without it. The results show that the deviation in system voltage can reach up to 14.62% during normal operation without a STATCOM device. In comparison, a STATCOM utilizing a PI controller is able to bring this deviation down to a maximum of 5.9%. Additionally, the STATCOM incorporating a FLC surpasses the performance of the PI control-ler, reducing the deviation at all system buses to levels not exceeding 4.67%.