On line diagnosis of capacitor switching effect to prevent voltage collapse

Emergency actions are performed to recover voltage after a disturbance. The optimal emergency actions are calculated immediately after disturbance based on the current state and applied when the calculations are completed. But because of the dynamic nature of the loads, the system state is changed in this interval, so the calculated actions may no longer be effective. This paper presents a method to fast distinguish the emergency action effect to recover voltage. This is based on the measurement of actual load powers and voltages in the instant the actions are applied and using the concept of attraction region. The diagnosis can be only performed by algebraic calculations, but a short dynamic simulation is sometimes required. The focus is on the capacitor switching as a common used emergency action, but the results can also be used for the other actions.