Study Of Calulation And Experiments Of Ampacity Of10kV Three-core XLPE Cables Laid In Pipes

With electric load increasing and underground transmission corridors becoming scarce,cables are used widely in the urban power network because they beautify the city and havehigh reliability. Pipe laying has been an important way relying on the ability ofaccommodating more circuits and resisting the external damage. Ampacity is a vital parameter,and it can be divided into the current rating and the cycle current rating according to loadnature. Amapcity is beneficial for designs, operation and management of cables lines.Therefore, study of ampacity of three-core cables laid in pipes has important practicalsignificance.The paper studies calculation principle of cables laid in pipes, and a software ofcalculating ampacity is developed based on Visual Basic. Experiments of the current ratingand the cycle current rating are carried out in order to verify the software in test field. Thechange rules between cable depth, environment temperature, surrounding medium thermalresistivity, and circuits and so on are presented.Researches indicates that iterative method makes error between calculation value andactual value of air temperature inside pipe is less than1.5℃. Max relative error betweencalculation value and experimental value of the cycle current rating is less than5%. Thecurrent rating and the cycle current rating both are negative correlation with cable depth,environment temperature, surrounding medium thermal resistivity and circuits. The cyclecurrent rating is negative correlation with load factor. Its factor is negative correlation withload factor, positive correlation with circuits, and is little correlation with environmenttemperature.