In this paper

the influence of different structure features of oil-paper insulation current transformer on the loss of bottom shielding loss to earth is analyzed

the significance of bottom shielding loss factor measurement（to earth） of different types of current transformers to the fault diagnosis is summarized.It is pointed out that bottom shielding loss measurement has direct reference significance to diagnose the equipment damp

but different criteria shall be adopted based on the characteristic of current transformer with different structures and the damp position of the equipment can be predicated and corresponding elimination measures be adopted.