One of the issues presented by the distributors (Enel, Fenosa and Iberdrola) were the inverted power flows in substations and the difficulties to control voltage when distributed PV reaches certain penetration. This was specially the case for Enel Distribution, as they presented an example in Puglia of reverted power flow from +10 MW to -30 MW, consequence of distributed solar. In my opinion, although having much more distributed PV than spanish distributors (15,9 GW Vs 4,3 GW), was not as “worried”.
The issue I want to highlight here is actually the increase in PV penetration in distribution has the effect of reducing the load of distribution transformers, specially in the hottest moments, therefore reducing insulaton degradation (see IEC Thermal index and halving interval in IEC 60216). This can actually increase the life of these assets, benefitting the distribution company.
It’s true that when power flows become reversed, and higher than normal consumption load, the effect is reduced lifetime, but up to this “reverted-equivalent-load” point it is of interest to the distributor to have additional distributed generation. Moreover, where losses influence the distributor’s regulated income, having enough PV to reach a load-consumption zero-sum as much time as possible during the day is in it’s economic interest (as in the following graph).
In my opinion, distributors should set distributed generation targets per area in order to reduce their substation loads and increase their assets lifetime. Not too much intelligence (no smart grid hard/software) is required to manage this, just setting the best case generation in the distribution, and promoting/accepting connection points up to the most appropriate to their network.