The thermal conductivity of electrical-insulating materials and insulation systems

Abstract

The thermal conductivity of several electrical-insulating materials used in the insulation systems for windings in turbogenerators and hydroelectric generators, as well as of the Monolith-2 insulation system, was studied using the DTC-300 setup. A collector micaceous stratum (KIFE-A), carbon fiber, glass-fiber laminate with a semiconductor filler (STEF-P), epoxy (DER-438), PK-11 compound in a mixture with ED- 20 resin, and prepreg materials, which are also used for fastening windings when laying them down in a groove, have been studied. The temperature dependences of the thermal conductivity of the studied materials show a linear behavior in the relatively low range from room temperature to +150°C. The temperature distribution over the thickness of the plate that imitates insulation in a groove of an electric machine has been determined. It has been shown that a drop in the temperature between the heat source and the outer surface is a tenth of a degree. The temperature distribution in the groove with a length of 1.5 m and venting channels placed every 50 mm with two insulating rods with different means of fastening rods and insulation thicknesses has been studied using a model of a hydroelectric generator stator (U_w = 13.8 kV, power of 70 MW, Monolith-2 insulation).