Analysis of LN₂ cooling system and electrical insulation contraction for high Tc superconducting cables

The LN₂ cooling system for fully flexible three phase high Tc superconducting cables was addressed in this paper. Explicit formulas were presented to calculate the cooling capacity and stability. Thereafter, the stress cracking and the thermal contraction of electrical insulation at low temperature were analyzed theoretically and experimentally. The thermal contractions of the ultra-high molecular weight polyethylene insulation layer of short model cables were measured with the moire method and strain gauge method. The measured result was in good agreement with the theoretical result. Both the theoretical and experimental results confirmed that the insulation does not suffer from the stress cracking problem on cooldown, and it is an excellent candidate for the electrical insulation at low temperature