The reliability and quench process of superconductor cable

Two superconductor cable samples were tested under overload current and the quench behavior of the cables was investigated. The results showed that the quench first began at the weakest spot on the cable and propagated depending on the surrounding thermal conditions. Local thermal runaways, which could permanently damage the cable, would occur if heat is accumulated in small areas. The phase shift angle between the current and voltage could be used as a quench indicator to avoid the thermal runaway, because this angle is especially sensitive to resistance changes in the cable. The cable was quite strong to withstand overload inrush current. The overload current, double of the critical current and lasting 3 s, will not degenerate the performance of the cable. However, too much overload current does impair the cable, or causes its critical current to decrease.