Development of 500-KV AC Cable Employing Laminar Insulation of Other Than Conventional Cellulosic Paper. Final Report

摘要

The results of an investigation to develop a 500 kV ac laminar dielectric power cable and joint having insulation with lower losses than conventional cellulosic paper insulation are presented. Background information is presented on proposed low-loss synthetic and composite synthetic/cellulosic paper insulations. From these studies, fibrous polypropylene paper tape and cellulosic paper-polypropylene film-cellulosic paper composite paper (PPP) were chosen. Extensive testing of hand-wrapped cable models fabricated with each type of tape served to eliminate the fibrous polypropylene paper tape from further consideration. Cable model tests indicate that the PPP tape is satisfactory for insulation in 500 kV ac cable, and that oil impregnants now used in conventional cellulosic paper insulated cables are unsuitable, but that silicone oil with an additive is satisfactory for PPP tapes. Laboratory data indicate that it may be necessary with the PPP tapes to use a significantly lower viscosity impregnating oil which has a greater tendency to drain from pipe-type cables than conventional oil. This may require a modification of the moisture seal. Four final pipe-type cables having a conventional moisture seal were manufactured for possible future field testing. The dielectric loss of the final cables is one-fifth that of conventional cellulosic paper insulated cables. The estimated installed cost per MVA-mile of the PPP insulated cable, neglecting losses, is higher than cellulosic insulated cables impregnated with conventional mineral oil. However, the capacitance of the cable insulated with PPP tape is 25% lower than conventional cable, and therefore, the reactance necessary to compensate for the cable charging current is significantly reduced. (ERA citation 05:036641)