Residual Magnetic Flux in High Resistance Grounding System

When transformer is being energized a large magnetizing inrush current flows depending upon the closing phase of circuit breakers and the residual magnetic flux in the iron core. One of the suppressing the magnetizing inrush current method is to control closing phase of the circuit breaker. For the controlled switching, it is essential to grasp condition of residual magnetic flux in the iron core. Ample studies show the residual magnetic flux for no-load transformers. The residual magnetic flux for three-phase and three-leg transformer had been investigated. However, little is known about residual magnetic flux of transformer of high resistance grounding system. In this paper, the residual magnetic flux of transformer using in high resistance grounding system was investigated by experiments and calculations.