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NETWORK / 20 / JULY/AUGUST 2017 'G reat Scott! 1.21 gigawatts! 1.21 gigawatts!" Although these are the words of Doc- tor Emmett Brown from the Back to the Future trilogy, here at NIE Networks we are proclaiming a similar message. The Doc had to harness a lightning strike to provide this power, but a more feasible approach has been devel- oped to supply the customers of Northern Ireland: distributed generation (DG). Realising that a shi‡ in Northern Ire- land's energy mix was necessary to address concerns about climate change, the then Department of Enterprise, Trade and Indus- try in 2010 suggested an ambitious target for Northern Ireland: that by 2020, 40% of the electricity consumed in the country would be generated by renewable resources. With an interim target of 20% by 2015 already met, Northern Ireland is well on track to meet the 40% target. When 1.21GW of connected renewable DG, which was achieved in March 2017, is viewed in the context that Northern Ireland experiences a summer valley electrical demand of about 0.5GW and a winter peak of about 1.8GW, it is easy to appreciate the proliferation of connected DG in Northern Ireland. The renewable DG energy mix is shown in the pie chart opposite, demon- strating that wind energy is the current larg- est renewable sector in Northern Ireland. In fact, on 11 January 2017 a record-breaking 60% of all electricity generated on the island of Ireland was from wind. Out of the west Most of the wind generation is in the west, a result of the higher wind speeds in that region, but that creates difficulties in trans- porting it to the load sinks in the east. The emergence of DG has changed the passive distribution system to an active one, with bi- directional power flows at many substations. Consequently, throughout the country but particularly in the west, a large number of primary substations (33/11kV) that were originally designed to serve only customer load, have now reached saturation point be- cause of reverse power flow or other techni- cal limitations, meaning that in the absence of further substantial investment, extra DG connections cannot be facilitated. The impact, however, is not only limited to the distribution network, but spreads into the transmission system. In early 2015, the effect that the large quantity of connected "small-scale generation" (less than 5MW) was having on the transmission system was realised, as saturation began to be expe- rienced at bulk supply point substations (110/33kV) and on the 110kV network. This means that every application that comes through must be analysed at each voltage level, starting from the top, to calcu- late their impact on the network. The transmission system heat map below, produced by SONI (System Operator for Northern Ireland), shows broadly where the last remaining generation capacity was identified on the transmission network in early 2016 (about 200MW indicated by the green area), with the transmission network (red area) in the west now completely satu- rated with DG. NIE Networks, along with SONI, are in the latter stages of finalising the allocation of this limited capacity to applicants – this is likely to take connected DG capacity in Northern Ireland in excess of our peak system demand of 1.8GW. The sizeable role of managing the inte- gration of DG has fallen on NIE's networks' connections department, which has had to develop and evolve innovatively to cope with the huge demand of applications over recent years. Fair and consistent When an application is received, the proposed project joins a complex queuing process that serves to treat applicants in a fair and consistent way. When it is released from the queue, a design engineer consid- ers power flow, voltage levels, fault levels and harmonic components in their design, before passing the project to a planning engineer who plans the job. A connection ConneCting renewable generation Northern Ireland transmission system heat map The transmission system heat map produced by SONI show- ing the remaining generation capacity on the 110kV network in early 2016. The green area indicates about 200MW of capacity, but the transmission network (red area) in the west is now completely saturated with distributed generation. Republic of Ireland Northern Ireland