Aging of lapped tape insulated model cables at cryogenic temperature

High temperature superconducting (HTS) power cables are generally divided into two generic designs, cold dielectric and warm dielectric. In the cold dielectric design lapped tape insulation and liquid nitrogen are used in combination to provide the electrical insulation between the conductor and the ground shield of a HTS cable. Using non HTS conductors, lapped tape insulated model cables have been tested at high voltage, including AC breakdown, negative impulse breakdown, and long term aging under AC stress. Two high voltage cryostats have been built for short and long term aging studies that permit testing model cables under the combined conditions of high electric stress, cryogenic temperature and elevated pressures up to 15 bar. A log-log plot of electric stress versus time-to-breakdown has yielded a linear curve having an "n" value indicative of cable life performance. For data obtained thus far, aging experiments (ranging from a few minutes in duration to several weeks) have yielded an n value of 26.2. Since aging at cryogenic temperatures is not expected to have a thermal cause, dielectric wear in HTS cables reduces to partial discharge as the primary cause. Phase and amplitude resolved partial discharge data of model cable in liquid nitrogen are also presented.