PURPOSE: To restrain static electricity from being accumulated by means of a simple method by lowering resistance value on the surface of one part of insulating paper.

CONSTITUTION: This apparatus is constituted by oil-impregnated paper 7 as insulating paper, an oil space 8, an oil flow 6 on the surface of the oil impregnated paper, a low-resistance film 9 formed on the surface of the oil-impregnated paper and charge relaxation routes 10. Accordingly, static electricity is generated only a little; a positive charge and a negative charge of the generated static electricity flows through the low-resistance film 9 and is relaxed by the charge relaxation routes 10; the static electricity is hardly accumulated. By this setup, it is possible to restrain the static electricity from being accumulated by means of a simple method.