the tape forming insulation layer 26 if the intense voltage stress is concentrated on layer 26 the layer 28 will adequately serve to provide the protection from the dielectric stress required by the groundwall insulation system and because the voltage stress concentration has been dealt with by layer 26 the overall groundwall insulation system is still quite functional and much less expensive than if insulation layer 26 had been employed exclusively for the groundwall insulation system the insulation of fig3 is functional and cost efficient and thus provides a more effective and efficient groundwall insulation layer the groundwall insulation comprising layers 26 and 28 may be subjected to press curing or an autoclaving curing process to eliminate any voids in the insulation layers 26 and 28 and to subsequently drive the resin impregnant to gelation suitable surface coatings may be applied to the external surface of insulation layer 28 once it is cured fig3 b shows the composite groundwall insulation as it applies to coil 20 composed of three turns in this instance the copper conductors 22b are surrounded by strand insulation 24b the turn insulation 25b is applied to each turn and the initial layer of groundwall insulation 26b containing the same constituents as layer 26 in fig3 a is applied finally the layer of outer groundwall insulation 28b is applied with the exception of the presence of the turn insulation 25b the insulation systems of fig3 a and 3b are very similar in summary a groundwall insulation is disclosed which utilizes a pair of insulating materials in a most efficient manner the material which.