Mengesha, Mamo (PhD)Gebrmichael, Gebrie2018-12-212023-11-282018-12-212023-11-282017-01-20http://etd.aau.edu.et/handle/12345678/15215An increase of power demand in recent years have developed a number of challenges for power system engineers, for increasing the power transfer capability of the already installed transmission system without the expansion of the existing or building new transmission networks. Flexible AC transmission system devices such as thyristor controlled series compensator can help increase power transfer capacity in heavily loaded networks because of its capability to control power flow flexibly. This is where TCSC device is very useful because of its low initial cost as compared to setting up a completely new transmission networks. The TCSC technology makes use of the already installed generating and transmission systems with minimum line losses and maximum use of the existing system. The thesis analyses the importance of TCSC which is Series Compensation for the improvement of transmission line utilization at Dedesa substation of 500kV transmission system stretched from GERD to Holeta substation and designed TCSC for the system as good alternative for power oscillation damping and SSR mitigation. The system is implemented using software. Steady and dynamic stabilities power, voltage and current of the system are improved using DigSILENT. Generally, using TCSC the power capacity is increased from 5759 MW to 5916.35 MW, voltage regulation is decreased from 3.95% to 3.02% and it is 10% of the building of new transmission line which is cost effective method. With the firing control of the thyristors, its apparent reactance is changed smoothly and rapidly for stability system from 83.60-157.72Ohms.en-USSeries CapacitorFSCTCSCMOVStabilityDedesa Substationpower transfer capacityThesis