T The economic development in East Kalimantan is growing rapidly along with the growth of population and industry that need for power becomes a very important thing. Therefore it needed a system with a reliable and guaranteed duality. Power systems in East Kalimantan are connected into one system of 150 KV afready complex making it susceptible to disturbances, disturbances originating from both internal and external. An electric power system must be able to guarantee the availability of electrical power Ripply without disconnection of any load connected to the system. Disturbance can cause the system to become unstable, that could harm consumers, especially industrial consumers. To improve the stability of the system if there is disturbances with immediate disconnection from the compromised system. And calculate the maximum power transfer. The pui pose of this research is to find the factors that affect the stability of the rotor angle. To get the critical clearing time and which channel to respond quick& during disturbances in the transmission line system of East Kalimantan. And to know how to make the system avoid interference from that can cause a blackout with the help of a simulation program Digsilent. The results show that the factors that influence the stability of the rotor angle of the systems include fault location, loading, time of termination and reactance channels. After you know when the breaker critical in the electrical system of 150 kl7 East Kalimantan, plants that are in line A/langgarsari - New Industry is experiencing the fastest response against harmful for peak periods, while outside peak load power plants that are in line Karang foang - New Industry experiencing the fastest response to disturbances critical clearing time. So that the electrical system to avoid a total blackout, then to coordinate the GB as a safety should be set according to the time critical breaker so the system can continue to run so that the process of distributing electricity to consumers well.