Limits set by component loadability on solar power integration in distribution networks

This paper proposes a number of deterministic and stochastic approaches to quantify the hosting capacity of the distribution network for solar photovoltaics (PV) units when that hosting capacity is limited by the loadability of feeder cables or distribution transformers. Such approaches should be used as input to investment and planning decisions by distribution-system operators. Distribution networks from two areas in Sweden supplying 309 MV/ LV distribution transformers with 12,000 customers downstream have been used to illustrate the different ap-proaches. By defining a break-even length, it is shown that both overload and overvoltage may limit the hosting capacity. The results obtained for the 309 networks show that the overload limit is more often exceeded for transformers than for feeder cables for smaller solar PV sizes. For larger solar PV sizes, feeder cables are likely to be overloaded before the transformers. A stochastic hosting capacity is calculated for 170 of the 309 distribution transformers and compared with a deterministic definition of the hosting capacity. It is shown that the deter-ministic definition corresponds to a 50% risk of overloading. Both deterministic and stochastic definitions show that transformer overloading is very unlikely as long as the probability of customers installing solar PV is less than 20%.