Abstract :
If a tunnel is buried at more than 10 meters deep, it is known that the value of thermal resistance of soil calculated with equation of transient state is smaller than that calculated with the Kennely´s equation, which is the equation of steady state. We, however, hadn´t verified the propriety of this theory by using data of actual transmission line yet. Therefore, in calculation, we adopted a multi-step equivalent thermal circuit in which the value of thermal capacitance of soil and variety of load could be taken into account and we tried to verify the propriety of this theory. Moreover, to calculate exactly, we considered heat removed by water-cooling system and change of ground soil temperature. We calculated the deep part of the tunnel. The calculated result was almost equal to that of actual measurement. We confirmed that the multi-step equivalent thermal circuit was proper to this case.
Keywords :
XLPE insulation; cooling; heat radiation; power cables; power transmission lines; soil; specific heat; thermal resistance; underground cables; underground transmission systems; 154 kV; Nanko Karyoku transmission line; XLPE cables; cable loss; cooling system; ground soil; indirect forced cooling system; inlet temperature; outlet temperature; thermal radiation theory verification; thermal resistance; volumetric specific heat of soil; volumetric specific heat of water; water flow rate; Capacitance; Distributed parameter circuits; Equations; Power system transients; Soil; Steady-state; Thermal loading; Thermal resistance; Transmission line theory; Water heating;
