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Abstract: This paper focuses on increasing stability and maximum loadability of a system by considering the op-timal location of Flexible AC Transmission Systems (FACTS) devices in multimachine power system. Identification of a suitable location for installation of (FACTS) costly device is a vital task; several criteria are to be satisfied be-fore selecting the best location.Two types of (FACTS) devices, static var compensator (SVC) and thyristor con-trolled series compensator (TCSC) can be installed on buses and transmission lines respectively. Improving the sys-tem's reactive Power handling capacity via (FACTS) devices is a remedy for prevention of voltage instability and hence voltage collapse using continuation power flow (CPF) method to find the best location of shunt (FACTS) de-vice then evaluate the effect of this device on the system. Also the continuous change in power demand and supply altered the power flow patterns in transmission networks which raise serious challenge in operating the power sys-tem, to prevent this problem series (FACTS) is used, using optimal power flow (OPF) method to find best location then evaluate the effect of this device on the system by using (CPF) method. It will perform the control of power flow with (FACTS) devices on the test system and also the time domain simulation for three phase fault applied, the simulation is made without and with (FACTS) devices. The effectiveness of the method is tested and illustrated on IEEE 14-bus system. Power System Analysis Toolset (PSAT), a computational tool under Matlab program for effec