th International Conference on Electricity Distribution Turin, 6 -9 June 2005 C I R E D DISTRIBUTION NETWORK INTERCONNECTION FOR FACILITATING THE DIFFUSION OF DISTRIBUTED GENERATION G. Celli*, F. Pilo*, G. Pisano*, V.Allegranza † , R. Cicoria † * Department of Electrical and Electronical Engineering –University of Cagliari, Italy † CESI, Italy giuditta.pisano@diee.unica.it The foreseen increasing diffusion of Distributed Generation (DG) in the distribution networks is giving the impetus to the study of new network arrangements, with the aim at solving congestion concerns, voltage regulation problems, and eliminating barriers and obst ctive 54/2003 may constitute the necessary political play a new role and explicitly defines the DG as a resou sion issues. For these reasons many authors env of the transmission network, but it will chan oltage regulation, automation and network In the paper, considering been deeply studied both in steady state and t ngement on the exploitation of DG. In part feeders, closed loop laterals, interconnection bet e radial scheme. For each type considered, stea profile, to assess the short circuit level, to ev reliability. Examples derived from real disadvantages) of the po dynamic behaviour of a m converters). One of the m Critical Clearing Time (CC transients caused by short circuits) occ values of rotating units (Syn different inertia constant (H CCT of the generators su faulted area, allowing th DG connected with powe Syn Indu Keywords: Distributed Gene Session Number 5 PUBBLICATO A5018633 (PAD – 653496)PUBBLICATO A5018633 (PAD – 653496)

acle to the development of a new distribution system. The recent EU dire driver to accomplish these objectives because it calls distributors to rce to take into consideration for distribution planning and expan isage that the distribution system will be no longer a passive termination ge towards active networks. Interconnection, dynamic control of power flows, v reconfiguration are some of the most important features of active networks. the importance of interconnection in active networks, meshed schemes have ransient condition with the aim at pointing out the effect of network arra icular, different types of meshed distribution networks (closed loop trunk ween different feeders, etc.) have been examined and compared with th dy state simulations have been performed in order to analyze the voltage aluate losses and avoided costs for network upgrading and, finally, to asses grid

world are presented and discussed in order to point out the potential advantages (and ssible new practice of distribution grid. In particular, the greater attention has been paid to the ix of DG sources differently interfaced with the MV network (interfaced directly or with static ain findings of this dynamic study is that generally the more meshed is the network the higher the T) is. This means that some generators can keep in service during fault conditions (i.e. urred in interconnected networks. In particular, in the following table the CCT chronous Generators and Induction Generators) directly connected to the network, valuated for ) and for all the network configurations investigated, are reported. It is worth to notice that the pplying the meshed network, depending of their H, gives enough time to detect and isolate the e majority of generators being in service. Further studies will more deeply focus on the effect of r electronic converters in meshed networks. Table I: CCT [ms] of rotating DG units during a three-phase short circuit Meshed DG Units Radial Closed loop Weakly meshed 1 st 2 nd 3 rd chronous Generators H 1 =2s 195 195 193 193 193 H 2 =4s 270 270 265 265 265 ction Generators H 1 =0.3s 235 320 355 360 375 H 2 =0.6s 450 580 655 670 715 ration, distribution network planning, meshed and radial network schemes.