Measuring analysis of magnetization characteristic curve and exciting current of single-phase transformer under DC bias

As an important element in AC network, power transformers are often subject to some external disturbances. DC bias is one of those external disturbances and will take eect when 1) there is geomagnetically induced current[1-2] ( with a frequency less than 0.01HZ and resembling the DC); or 2) direct current transmission system is operated by means of unipolar ground return. Under this circumstance, it will generate a DC potential distribution[3-5] on the ground and disturb all the neutral directly grounding power transformers within that range.