Design Of Power Cable Load Flow Analysis System Under The T Condition Of Integrated Laying

The current growing social demand for electricity requires higher reliability for transmission lines. The electricity power cable is the most widely used carrier. Due to the operating conditions, laying and the surrounding environment and other factors, the power cable ampacity is difficult to determine; to accurately calculate the ampacity of cables under a variety of laying is significantly important for the safety, reliability and economy of cables.The relationship between temperatures and XLPE cable insulation conditions and the ampacity is analyzed in this study, and based on the basic principles of heat transfer, a mathematical model between the external environment and the ampacity was constructed.Firstly, according to the model, the theory about the ampacity calculation formula was studied and the importance of external resistance to the entire ampacity calculations laying in different ways were analyzed. At the same time, compared with the IEC standard, which considered the the thermal resistance between cable conductor to the metal suite as unfied insulation resistance, the thermal resistance calculations under the metal sheath was devided into the material resistance of different cable layers, thermal contact resistance between the material and the thermal resistance of the air layer in this paper. For the optimization of the external thermal resistance under various laying conditions, the measured ambient temperature, surface temperature and the metal cable sheath temperature were introduced,and then the cable conductor temperature was calculated to be compared with the experimental values. Then based on the cable laying environment, the loss and the body structure of each layer, a calculation method of conductor temperature depending on the ambient temperature of laying conditions and the cable outer skin temperature etc. is deduced. The accuracy of above method was illustrated applying the optimization method to calculate the conductor temperature under soil buried condition. Finally, an analysis system of cable ampacity under different laying conditions was completed and related function tests were carried out.