| With the reconstruction of power grid, power cable replacing overhead lines has become a trend recently. And one of the key problems, which involves the security and economic operation of the cable, must be addressed is the ampacity calculation. Precise thermal parameters of the surrounding medium around cable should be offer if the power department desired to acquire the accurate ampacity. Therefore, the estimation of surrounding medium thermal parameters has a very important practical significance.According to cable system thermal circuit model, a real-time skin temperature calculation method was proposed. And then particle swarm optimization(PSO) algorithm was introduced to optimize the surrounding medium thermal parameters, so that the calculated skin temperature and the measured skin temperature can match each other. In order to verify the calculation methods of skin temperature and thermal parameters, temperature rise experiments and the finite element(FEM) method simulation based on COMSOL Multiphysics were carried out.The results showed that the surrounding medium thermal parameters, which were estimated by adopting the combining method of PSO algorithm and thermal circuit method, can be used for the skin temperature calculation, and the calculated skin temperature and the measured skin temperature were consistent. When the thermal conductivity and specific of soil converted from the estimation results were loaded into the FEM models, the simulation results and measured skin temperature were of good consistency, which verified the correctness of the methods proposed in this paper. The calculation methods does not have to consider the cable laying, temperature and humidity of the surrounding medium, and the estimation process is simple and intuitive. The method proposed in this paper can be used to help the power department to understand the actual environmental conditions around the cable and accurately calculate the ampacity. |
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