A method for determining the current-carrying capacity and durability of power cables based on variable ambient temperature and solar radiation

Abstract

Modern power networks contain a large number of distributed energy sources, particularly photovoltaics. In the case of photovoltaic sources, the associated electrical installation components, including cables installed in free air, are exposed to solar radiation and significant ambient temperature variability. In the classical approach to calculating the current-carrying capacity of power cables in free air, a constant ambient temperature is assumed and the direct influence of solar radiation is usually not considered. Such an approach, under certain conditions for a given country, may lead to an underestimation of this capacity (a cold region of the country) or an overestimation (an exceptionally warm region of the country). This paper proposes an alternative approach for determining the current-carrying capacity of power cables. The concept takes into account daily and annual fluctuations in ambient temperature. This is based on actual data obtained from measurements with a measurement step of one hour. As a case study, the results of calculations for sample weather scenarios for northern Poland are shown. The analysis indicates that under certain real-world conditions, cables may be overheated, which reduces the durability of their insulation. For the case of non-rated ageing of cable insulation due to high temperature, a current-carrying capacity correction factor was determined. This approach, different from the normative scheme, allows for determining the thermal exposure of cables that is close to the real one. The analysis results can be useful in designing electrical installations, particularly when components are located on the building facade or roof.