Current Sharing in Spiral Copper-Plated Multifilament Coated Conductors

We experimentally studied the influence of current sharing among filaments on the initiation of thermal runaway and protection against it in a multifilament coated conductor wound spirally on a round core. We artificially introduced a local defect near one edge of a 4-mm-wide multifilament coated conductor as well as a monofilament coated conductor by using a fine drill bit. We wound each coated conductor on a glass fiber-reinforced plastic (GFRP) core and set several voltage taps on their both edges to measure the voltages in longitudinal (both edges) and transverse directions. We compared thermal runaway current, above which thermal runaway initiates, of multifilament coated conductor with that of monofilament coated conductor. We also compared their time constants of current ramping down, below which the coated conductors are protected against degradation after thermal runaway.