The stability of the power system is the ability of an electricity system to give his reaction against a disruption in normal working state as well as returning to normal in original state. Frequency stability depends on the ability to restore balance between load and generation system by minimizing load discharge. As a company angaged in the field of petroleum and gas, PT Pertamina (Persero) RU IV Cilacap prioritize service needs for the electricity productios process. To maintain the sustainability of the production process needed a reliable power system. To maintain the stability of the power system due to the loss of a generator of electric power system, PT Pertamina (Persero) RU IV Cilacap did the release of load, the load is a load which when removed do not interfere with the process of the production of the refinery. After the release of the load by using UFR (under frequency relay), power system can be back to normal according to the standard power system PT Pertamina (Persero) RU IV Cilacap.