New Method for Mitigating Magnetic Inrush Current of Transformer by Neutral Grounding Resistor
ZHU Ke, Wilsun XU, TIAN Lijun, QIN Yinglin (Shandong University, Jinan 250061, China)
This paper presents a new, simple and economical method to reduce magnetic inrush current caused by transformer energizing. The method uses a grounding resistor connected at the transformer neutral point and delayed energization of each phase of the transformer. The characteristics of peak inrush currents affected by the neutral resistor are analyzed and the formula for obtaining the optimal value of the neutral resistor is given. The method proposed has been tested by experimental simulation. The experimental results show that the new method has a performance similar to that of the resistor pre-insertion scheme, but it will be much less expensive since there is only one resistor involved. The level of the magnetic inrush current reduction depends on the value of the neutral resistance and the transformer parameters.