Out-of-step protection in power system

Power system protection requires the isolation of a healthy part of the power system from the faulty section. If a fault is detected before its occurrence, then corrective action could prevent much damage to the system and results in a reliable power supply. Out-of-step (OOS) is a condition in which certain disturbances in the power system can lead to a loss of synchronism between parallel operating generators or between different areas of the power system. Such conditions, if detected, in a timely manner could prevent the system from collapsing and finally blackouts. This chapter prevents a detailed survey of OOS protection in power systems.