Direct Current Ampacity of 35 kV Alternating Current Cross-Linked Polyethylene Cables Under Various Direct Current Topologies and Laying Environments
Converting alternating current(AC)cables into direct current(DC)operation is of great significance to achieve new energy generation connected to the grid and increase power supply capacity.A 35 kV AC cross-linked polyethylene(XLPE)cable was taken as the research object,and temperature field simulation of the three-core AC cable was carried out through the finite element method under three kinds of DC topologies:three-wire bipole,monopole,and bipole.At the same time,common influencing factors in the distribution network were considered,such as distance from hot water pipes,cable cluster laying,and current imbalance,so as to explore the influence of these factors on the ampacity of the cable when the AC cable was changed to the DC operation.The results show that under the same operating temperature,the 35 kV AC XLPE cable has the smallest ampacity when operating under the monopolar DC topology and the largest ampacity under the three-wire bipolar DC topology.When the horizontal distance between AC cable and urban water supply pipes is 2.0 m,and the vertical distance is 0.5 m,the ampacity of cables operating under the above kinds of DC topologies is reduced by about 3.0%.The maximum ampacity can be increased by 90 A as the asynchronous peak value is loaded when the cable cluster is laid.The cable ampacity increases first and then decreases with increasing current imbalance,and it reaches the maximum value when the current imbalance is 0.The research results can provide some reference for converting 35 kV AC XLPE cables into DC operation.
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