Restarting scheme of electrical motors after supply voltage outages in heavily loaded industrial facilities

A primary goal of an industrial electric power system is to minimize production losses in industrial facilities maintaining the industrial process running after the occurrence of certain supply disturbances. The automatic motor restarting is one of the strategies used in the industrial facilities, especially in Oil and Gas facilities, in order to achieve this goal. Aim of this strategy is to allow that after a voltage dip or disturbance, the medium voltage and low voltage motors will be automatically reenergized within predetermined time and in a certain order when voltage is restored. These abnormal voltage conditions may be caused by cleared short-circuits upstream, generation and public supply voltage outages or a simple automatic transfer system of a selective secondary substation operation. This paper presents the automatic motor restarting scheme applied at a large oil refinery where more than 600 motors are assigned to automatic restarting. Application criteria for motor restarting, power system simulations and physical implementation of this scheme are discussed in this paper.