Status of Superconducting Fault Current Limiter in Italy: Final Results From the In-Field Testing Activity and Design of the 9 kV/15.6 MVA Device

Ricerca sul Sistema Energetico-RSE S.p.A. has recently accomplished a more than two-year-long in-field activity on the first Italian superconducting fault current limiter (SFCL). In order to carry out the in-field activity, a 9-kV/3.4-MVA SFCL device was installed as single feeder protection inside the Milan MV distribution grid; further to this first success, the development of a new device to be installed in the same substation, but as a transformer protection, has been already initiated. After having briefly summarized the final result of the in-field activity on the 9-kV/3.4-MVA device, this paper is mainly focused on the new 9-kV/15.6-MVA upgraded device: in particular, the first small-scale HTS winding prototypes will be described and the power tests implemented to validate their performances will be discussed. The test results allowed to identify the best layout, consisting in two parallel-connected coaxially arranged 2G windings, each made of two layers anti-inductively wound on a fiberglass cylinder, and each featuring a total 2G tape amount of 96 m. The actual research plan foresees to install the upgraded device in the live grid in 2016.