Prediction of Heating Power in Magnetic Pipe Conducting Large AC Current With High Frequencies Up to 200Hz.

In direct electrical heating system (DEHs), which is developed for subsea process to safeguard well stream through pipelines to topside process platform or shore, the production pipeline is also acts as an active conductor conducting large AC current to generate heat. The heating source is conductive and hysteresis power losses in the pipe. Currently, the all implemented DEHs operate at 50Hz. There is a potential to further improve the heating capacity of the DEHs by operating the system at higher frequency so that the same power can be achieved at lower current. Consequently, the cross-session of the power cable can be reduced. Furthermore, operation in higher frequency directly results in better system utilization and less AC corrosion of the pipeline. This will further reduce the installation and operational cost and increase the system lifetime. For DEHs design it is critical to predict the heating power as function of input current and frequency so that proper frequency and current can be selected correspondingly. This paper analytically evaluate the heating power as functions of current and frequency based on experimentally measured material properties such as mass density, conductivity, B-H curve and hysteresis B-H loop energy. To verify the analytical results, both FEM simulation and prototype test are performed.