There may be capacitance between the high-voltage and low-voltage windings of the 11kv single phase transformer, between the low-voltage winding and the core, between the core and the tank wall. Charged transformer winding through the coupling of the capacitor, it will cause the iron core to the (tank wall) to produce a certain floating potential, due to the various metal parts within the dry cast resin transformer and the fuel tank wall ranging from the same, the suspension potential is different, To a certain potential difference, it will on the (tank wall) discharge, a direct result of core insulation damage. Therefore, the transformer core must be reliably grounded.