Advanced composite dielectric materials for use in the transmision of electrical power by direct current

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Standard industry tests coupled with in-service experience have commonly been used to develop insulator designs for high voltage alternating current (HVAC) transmission lines. For the most part, conventional ceramic insulators have been used on HVAC transmission lines for the past 100 years or so. Today, insulators that are made from polymeric materials (polymer insulators) are gradually replacing the older ceramic insulators. Polymer insulators have been developed in this way for HVAC and are currently used in limited numbers on high voltage direct current (HVDC) transmission lines. In light of increased global interest in HVDC transmission, polymer insulators for HVDC have become an unknown entity, as no standard industry tests have been developed for HVDC. In this research program, polymer insulators for HVAC are assessed for use at HVDC using the standard tests developed for HVAC, but suitably modified for HVDC, both for suitability of polymeric material and insulator design evaluation in terms of being able to withstand the environmental conditions conducive to aging of polymeric materials. The research program will initially examine the inclined plane test (IPT) that has been developed specifically for AC and suitably modifying the test for DC. This step highlights the differences in aging mechanisms of polymeric materials, between AC and DC, and validates the use of AC polymeric insulation materials at DC. The electrowetting mechanism of surfaces, which is a major factor in aging of polymeric materials, is to be investigated and compared at AC, +DC and -DC. The two common polymeric materials for HVAC insulators, silicone rubber and ethylene propylene diene monomer, will be studied with various fillers and filler levels using the IPT at DC. Insulator design, for DC will be investigated in a salt-fog environment and existing designs for AC will be examined for use at DC at similar aging conditions. Modifications to insulator profile and material for optimum performance is expected to be the outcome of the research program.