Power transformer is a crucial component in power system

and it is the most expensive equipment in substation. The nonlinear characteristics of transformer would result in significant magnetizing inrush current when closing a no-load transformer

and the current amplitude would reach up to dozens of times of the steady state current. In general

the decay rate of magnetizing inrush current is slower than that of short circuit current. Thus the high magnitude magnetizing inrush current would cause the maloperation of protection equipment in the transformer

the increase in mechanical stress of the windings

and the deterioration of the power quality.Fortunately

phase control closing of vacuum circuit breaker is a satisfactory solution to this problem. In this study

a test of closing no-load transformer by a 12 kV vacuum circuit breaker was conducted in the 6 kV direct test circuit of CEPRI. The magnetizing inrush current during random closing

common phase control closing

and phase control closing with calculating remanence was measured in order to verify the effect of phase control closing. The results indicate that the phase control closing

especially the phase control closing with calculating remanence

is effective in reducing the magnetizing inrush current compared with random closing. However

the prestrike characteristic of a vacuum circuit breaker influences the effect of phase control closing even though the phase control closing with calculating remanence is employed.