Current Distribution Analysis in Bi2223 Tapes of Superconducting Bipolar DC Energy Pipeline

Superconducting DC energy pipeline incorporates HTS DC cables and the LNG pipeline, and the overall efficiency is improved compared to the conventional HTS DC cables. In the energy pipeline, LNG is cooled down to 90 K at which Bi2223 tapes can still conduct moderate currents although the critical current density J
_c
at 90 K drops to about half of that at 77 K. According to the power law, three-dimensional models are constructed to investigate and contrast the current distributions and degradations on helical Bi2223 tapes of the bipolar double-core DC cables under different voltage levels. It is found that the current distributions on Bi2223 tapes tend to the sides which are closer to the cable of opposite polarity. Both the perpendicular and parallel magnetic fields on the surfaces of helical tapes are compared in ±100 kV and ±10 kV cables. The average degradations of critical current density of the cable influenced by the magnetic fields are estimated and the results indicate that the degradations of critical current density are similar with different insulation distance between poles.