Soil temperature profile due to stationary and transient operation of energy cables

Abstract

The supply of electricity, gas and water influences our daily life. All in all the population depends on a satisfactory functionality of these things. Plastic pipe are required to distribute gas and water. The operation of energy cables warm up the soil and may influence and mitigate the material of these plastic pipes. The focus of this paper is placed on crossings of energy cables and plastic pipes. Because of burial depth and low space arrangements under pavement areas it is not always possible to observe the distance between two different pipe systems. The distances can be in the range of 300 mm down to 100 mm, if appropriate measures are set. During the stationary operation with nominal current the energy cable produces loss heat and warms up the surrounding soil and might influence the material of other pipes e.g. gas pipes. Besides the normal operation of energy cables, a transient behaviour caused from an electrical failure produces additional heat in the trench and may cause mitigation on the gas pipe. The aim of this paper was to measure and investigate the temperature profile in the soil on a realistic test setup produced by different types of current stress. All experimental investigations were made in cooperation with an Austrian power utility. The test setup consisted of a medium voltage 20 kV 3-phase cable system with an overhead crossing gas pipe of PE in a distance of 100 mm. To get an idea of the temperature profile caused through the currents, 16 temperature sensors were placed in the volume close to the energy cable and plastic pipe. Appropriate measures as mentioned in the Standard were also tested to reduce the temperature on the surface of the gas pipe. A big number of test results was evaluated and proven on plausibility.