Design of Cryogenic Cooling System of a 35-kV/3.5-MVA Single-Phase HTS-Controllable Reactor

In order to compensate flexibly reactive power, it is necessary to develop a controllable reactor in long-distance and ultrahighvoltage systems. A 35-kV/3.5-MVA single-phase high-temperature superconductivity-controllable reactor (HTS-CR) is being developed. The control windings of the HTS-CR are made of HTS. The closed-cycle cooling method with the subcooled liquid nitrogen (LN) flowing in the cryogenic cooling system of the HTS-CR is introduced to cool down the HTS windings. The number and the layout of both the inlet pipes and the outlet pipes of the cooling system, which has great effect on the temperature rise of the HTS winding, are studied. Furthermore, the flow velocity of the subcooled LN of the inlet pipes is also investigated, which discloses the optimized structure design of the cryogenic cooling system. The study here is believed to provide some references for developing HTS-CR with larger capacity in the future.