Loss Test for a 5-m YBCO Cable Sample of the 22.9-kV KEPCO System Under Grid Operation

We have operated the 22.9-kV high temperature superconductor cable system installed at Icheon Substation of Korea Electric Power Corporation (KEPCO), which consists of a conductor and a shield using YBCO-NiW wires. We prepared the same 5-m cable sample as the Icheon Substation in order to understand its ac loss characteristic. Especially, the contact resistance between copper current leads and YBCO wires was minimized through the increased soldering surface between them. Besides, four voltage leads are attached to both the conductor and the shield with an equal angle of 90°. Under ac transport current, which was supplied to the conductor and shield in opposite direction, losses of the 5-m sample were tested for various contact positions of voltage leads, frequencies, and transport periods. The result shows that the measured ac losses for various contact positions in the conductor and shield are the same. However, their loss exponents are very different. More details will be presented in this work.