EMC challenges posed by distributed generation on protection

Distributed generation refers to electric power distribution networks in which generation or storage, versus loads, are quite well balanced, in contrast to the traditional distribution network that is simply a tree from a single supply source (the HV or EHV transmission network) branching out to plain loads.

Many studies have been made of possible effects of changed loadflow patterns on the voltage profile of the network or on the necessary settings for protection relays. What is of interest in this project is the more general sense of protection, including overvoltage-protection (surge arresters and voltage control) and current-limiting devices as well as conventional relays and circuit breakers, when there are power sources connected in the distribution network.

For example, how does the voltage change in a subtree of the network immediately after separation of that subtree from the rest of the network? This is surely very different with large amounts of distributed generation than with the traditional situation where there is none, but it will also depend on the type and the interface of the generation sources (induction generators in wind-power, power-electronic converters with various control strategies). And how tolerant are system components of brief `surges' of voltage amplitude? (there is much existing work and standardisation here).