GRADED ELECTRIC FIELD INSULATION SYSTEM FOR DYNAMOELECTRIC MACHINE.

摘要

There is disclosed a groundwall insulation system for use in dynamoelectric machines carrying voltages above 4 kV and preferably in the order of 13.8 kV, or higher. The groundwall insulation comprises two layers of insulation wound onto the conductors of the high voltage winding. The first layer of insulation has a first permittivity that is greater then the permittivity of the second layer of insulation wound onto the first layer of insulation. As a consequence, at the juncture between the first and second layers there is a sharp increase in the electric field profile as seen through the groundwall insulation. This step increase in the electric field profile results in the electric field adjacent the conductor having a maximum magnitude that is less than that normally experienced by insulation systems in the past. By reducing the maximum magnitude of the local electric field profile within the groundwall insulation the life of the insulation and hence the electrical conductor is improved while at the same time permitting a reduction in the thickness of the groundwall insulation.