PURPOSE: To make it possible to correctly provide barriers using ring-shaped spacers which are engaged in such a way as being contact with the oil-dipped lead wires of the surface of inner barrier and are arranged with the specified interval.

CONSTITUTION: The spacers 21 are placed in contact with the surface of inner layer 11, namely on the surface of taping 9 or inner barrier 20 and are formed as the rings with specified thickness and width, allowing at its circumference the barrier 20 to be wound in the direction indicated by the mark X. In order to cause the cooling oil to flow into the space 23, the spacers are provided with the oil flowing holes passing through its axial direction, thereby realizing flow of cooling oil. As a method of arranging the spacers on the inner barrier or oil- dipped lead wire, the ring-shaped spacers are engaged with the outside of inner barrier and is brought to the specified position through the sliding thereon, followed by that the ring-shaped spacers are divided into two or more segments on the line of radius and these are attached to the inner barrier.