XLPE-insulated cables for medium voltages with WTR-insulation-laboratory tests and first use in networks

In the Federal Republic of Germany, the first cables with plastic insulation on the basis of polyethylene (PE) were manufactured and placed into operation in the sixties. They were double extruded and had an outer semiconducting layer of varnish of dry graphite. Despite some breakdowns which occurred (among others reasons due to water treeing) mainly on cables of the first production years, the experience with PE- and XLPE-insulation is good. The authors describe test methods aimed at examining the breakdown mechanism of organically-insulated MV cables