The effect of PV on transformer ageing: University of Queensland´s experience

Rooftop PV has an advantage that it can reduce the load supplied by nearby distribution transformers. This in theory should make the transformer run cooler, and therefore extend the remaining life of its paper insulation. However, the relative impact of harmonics on transformer life is sometimes neglected. In this article we present the findings of an analysis on the new rooftop PV installation at University of Queensland, in Brisbane. The load profile of three transformers was investigated, with IEC thermal models applied to estimate hot-spot temperature. The relative effect of PV on the weighted hot-spot temperature was investigated, and then a determination made on the likely loss of life. The harmonics injected by the PV was then explored.