Influence of heating dynamics of polymer insulation of medium voltage power cables on their performance

Abstract

Currently, global trends in the development of medium voltage cable networks are aimed at the introduction of cables with cross-linked polyethylene insulation. Such cables are innovative products of domestic cable manufacturers. Most often, single-core cables are laid in parallel in one plane. The article analyzes a number of significant features of cables with cross-linked polyethylene insulation, which affect the thermal regime both in working condition and in emergency operation, among which - the dependence of thermal conductivity and heat capacity of polymer insulation on temperature. Cable throughput, which is determined by regulatory models and average environmental parameters, provides only preliminary information about its heating, useful for comparing its throughput with other cables of the same type. For certain requirements and for innovative cable designs, it is necessary to determine the capacity according to thermal constraints in specific operating conditions. Thermal and electrical asymmetry must also be taken into account in the test conditions of cables intended for laying three single-core cables in the plane. The heating of medium voltage cables with crosslinked polyethylene insulation was studied [1], an experimental assessment of the influence of the distance between the cables on the asymmetry of currents and temperatures was performed using three single-phase single-core cables АПвЭгаПу 1х70/16–35with the same current direction. It is established that in the absence of longitudinal currents in electrically conductive screens, the current in the middle core can be practically taken as a basis. It is proposed to use the method of concentrated heat capacities for the analysis of cable heating by overload current, which allows to significantly reduce the test time in production conditions. The study aims to create a method for determining the allowable current of medium voltage cables in specific operating conditions.