Enhancing transformer dynamic rating through grid application of photovoltaic arrays

The application of photovoltaic (PV) arrays for electric power generation can be made more cost effective by capturing benefits beyond the traditional energy and capacity values of power plants. One of the most significant nontraditional benefits is the savings associated with the potential deferment of distribution substation transformer upgrades. Here, simulations depicting the interplay between PV array capacity, ambient temperature, transformer size, oil and winding temperature rise, peak load magnitude, load profile and loss of life, have been conducted for such an application. Tradeoffs between PV array capacity and transformer overrating gains have been assessed. The impacts of PV generation on the overrating potential of an actual 22.4 MVA bank transformer of the Salt River Project distribution substation in Phoenix, Arizona, USA were evaluated. The analysis demonstrated the feasibility of deferring the addition of another bank in spite of a time difference of 2.5 hours between the substation´s peak load incidence and the time of maximum PV output