Laboratory Investigation on Phase Selection Closing Approach for Suppression of Inrush Current

During the no-load closing process, transformer will produce a magnetizing inrush current which will make the transformer relay malfunction and make adversely affect to the transformer equipment and power grid. Relative to a variety of external measures limiting the inrush current, the phase selection switch technology is more effective to reduce inrush current. The author analyzed inrush current by theory and dynamic simulation experiment. By controlling the closing angle to be less than 0° to 72° of the opening angle, inrush current is well suppressed.