Investigation of causes of dry-type transformer on-load tap-changer insulation

The article represents the analysis of the causes of damage on the on-load tap-changer of a dry-type transformer installed at a 35 kV substation under ground fault in a network with isolated neutral. In order to analyze these processes, the well-known technique of modeling transients in a transformer [1, 2] is supplemented with account of the interturn and interwinding capacitances of the transformer determined from the picture of the electrostatic field.