Helium / Nitrogen Refrigeration for the LIPA superconducting cable [ Return towards  References  ]

The LIPA project involves installing buried HTS superconducting cable over a length of 700m.
Air Liquide has supplied the cooling system for the superconducting cable, and the termination cryostats which, when placed at each end of the cable, not only connect it to the existing network, but also supply it with liquid nitrogen.
To ensure greater reliability, the cooling system includes a main helium refrigerator and a back-up system operating in open cycle with sub-atmospheric nitrogen.
This system with about 6 kW of capacity cools nitrogen circulating in the three cable phases to keep it at a temperature below its critical temperature: the operating temperature is around 70K.

The project must have an installation that offers very high levels of reliability, since the superconducting cable will be coupled to the city power grid for the first time. To meet this requirement, the proposed refrigeration system comprises a nitrogen refrigerator which starts automatically in the event of the helium system breaking down.
The design also had to be tailored to make allowance for the fault current and thereby protect the cable. This constraint was resolved by means of a buffer volume and tailored controls.
Lastly, the refrigerator is not set up in an industrial area, but in a residential urban environment. It is fully automatic and operates with just one regular inspection from an operating technician on the LIPA site.