Abstract
Low-voltage, as well as high-voltage power cable lines, are usually buried in the ground. The ampacity of the power cables in the ground mainly depends on the thermal resistivity of the soil, which may vary in a wide range. A common practice in power cable systems performance is to supply them from a pole of an overhead line. If so, a section of the line is located in free air and can be directly exposed to solar radiation. In some cases, the ampacity of power cables placed in free air is lower than in the ground. Differences in ampacities can be very high if thermal resistivity of the soil is very low, and simultaneously solar irradiation of cables in air occurs. This paper presents the risk of power cables overheating and in consequence the risk of their failure, when part of the underground power cable line is placed in free air. Temperature distribution of cables in the air (with and without solar radiation) for various load currents is presented. Thermal endurance of power cables insulation, operating with the overheating, is estimated.
Highlights
Distribution of power in power networks is performed with the use of overhead power lines as well as underground power cables
Given that the cable section in the air is connected in series with a section buried in the ground, the ampacity of the whole power cable line depends on the section for which thermal condition for heat transfer from the cables is the worst
This paper presents the problem of evaluation of the power cables ampacity and their insulation temperature when cables are placed in changing ambient condition “ground-air”, and especially solar radiation may occur
Summary
Distribution of power in power networks is performed with the use of overhead power lines as well as underground power cables. This paper presents the problem of evaluation of the power cables ampacity and their insulation temperature when cables are placed in changing ambient condition “ground-air”, and especially solar radiation may occur. The authors prove that thermal condition in the air can give a negative effect on ampacity and endurance of the whole power cable line, in particular when solar radiation occurs. It is very important in terms of the reliability of power supply, because, due to significant overheating of cables in air, fast destruction of their insulation may appear. On the base of the calculated temperature of the cables in air, a decrease in their thermal endurance is evaluated
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