There are several valuable performance measures for HTS cables that differ from conventional cables and are unique to the superconducting materials and their operating characteristics. These include:
This is defined as the amount of current (Amps) that the cable may carry while remaining in the superconducting state. At or below this value and the cable achieves near zero electrical resistance (see AC loss below). Above the critical current level, and the cable will begin to act like a normal, resistive material and electrical resistance will increase rapidly.
Superconducting materials carrying direct current (DC) are truly zero resistance. However in standard power networks carrying alternative current (AC) the materials do exhibit a very low level of resistance. This is due to the imperfect transport of the AC wave and hysteretic loss in the materials. This loss component is called AC Loss. The HTS wires themselves can be designed and manufactured with various levels of AC loss. Cable AC Loss is also affected by the detailed design parameters used by the manufacturer. Superior cable designs will have lower AC Loss. AC Loss is commonly measured in terms of heat generation per unit length, Watts per meter per phase (W/m/phase).