Distributed intelligence

摘要

New underground transmission and distribution cable circuits are expensive to install and difficult to site. Therefore, users are becoming more interested in accurately and confidently determining the maximum usable cable rating of existing lines for the full range of expected operating conditions. This is not easy. The cable environment can change significantly over the length of a feeder circuit because of differing thermal properties of the various soils encountered along the route. In certain locations, cables might be buried deeply (sometimes unknown to the design engineer), affecting the ability of the cable to dissipate heat. Heat generated from nearby distribution circuits also might raise the ambient earth temperature. Thermal conditions can even change with time because of moisture-dependent changes in soil thermal properties.