Live Grid Field-Testing Final Results of the First Italian Superconducting Fault Current Limiter and Severe 3-Phase Fault Experience

The first Italian Superconducting Fault Current Limiter 9 kV/3.4 MVA was developed and lab tested by Ricerca sul Sistema Energetico S.p.A. and then installed in the Milan distribution grid belonging to A2A Reti Elettriche S.p.A. This resistive-type SFCL device was operational since March 2012 and hence has been field tested for more than two years, providing a large amount of experimental data with a significant experience gaining. Some preliminary results were already presented; however, this paper reports on the main outcomes of the field testing activity including the effective short-circuit current limitation provided by this SFCL prototype during a severe real three-phase short-circuit event in the Milan distribution grid. The SFCL device showed to behave as expected, promptly limiting the short-circuit current by a factor of about 2. This is the first SFCL limiting action in Italy and one of the very first worldwide. Further to this first successful installation, the hosting utility A2A agreed to install in the same substation a new SFCL device protecting four different feeders, therefore implying a SFCL upgrading up to 15.6 MVA. Therefore, this paper also anticipates the key steps towards the development of the upgraded SFCL prototype to be commissioned in early 2015.