The present study analyses heat modes of high voltage cable lines typical for laying in the area of communications, different obstacles and engineering networks, such as, for instance, hot water supply lines. It is well-known that the load capacity of modern high voltage cable lines with a plastic insulation is limited by the maximum permissible heating temperature of 90 °C. This study focuses on two typical cases of heating mains influence on heat exchange of a power cable line with surrounding ground: 1) the rapprochement of a power cable line with a heating main – the segment of a parallel disposal of a cable line and a heating pipe; 2) the intersection of a cable line and a heating main – the area where the cable line going above the heating main crosses it at the angle of 90 degrees. We have proposed the model of a prolonged cylinder with inhomogeneous thermophysical and heat exchange parameters distribution along this cable for the temperature distribution along a power cable in terms of non-regular laying. The finite-element method has been used to solve the problem of cable line heating fields near heating main calculation. A quantitative analysis of the cases described above has revealed that the local cable temperature excess up to several tenths of degrees is typical for them. It leads to the transmission capacity decrease by 20–30 % and limits the cable line ability to cover peak loads occurring in industrial, natural or other disasters. Besides, cable line segment spillover out of permissible temperature mode leads to emergency, power shortage and further repairing efforts. While engineering and calculations of the cable lines modes, our proposed techniques allow avoiding critical temperature conditions which may lead to the consequences described above.