Studies on Heating of Electrical Insulating Paper

(Part 3) Effects of Heating on Mechanical Strength under Dry Condition

Abstract

Mechanical behavior of the paper for power cable under dry condition was studied. The samples w ere impregnated with insulating-oil or microcrystaline wax after drying, and tensile strength, elongation, folding endurance, bursting strength and tear resistance were measured.
(1) Comparing the mechanical strength under dry condition with that RH 65 %, there was remarkable change in the elongation of C. D (cross direction) and the folding endurance of both directions, C. D and the M. D (machine direction). Especially, the folding endurance of M. D showed the decreases of about 98%.
(2) The order of properties which had been effected by heating was as follows;
folding endurance>bursting strength>tear strength>elongation>tensile strength.
(3) Comparing the heating in the air with that in the vacuum, so much difference was not approved by heating of 110°C and 130°C in all the properties, but remarkable change was recognized at 150°C.
(4) Some difference was shown on the extreme decrease both direction, M. D and C. D by heating and remarkable difference was shown in the folding endurance and elongation by heating in the air.