  There are different MV grid concepts with regard to mode of operation and
protection system layout. The increasing installation of DG raises the question
if the currently used concepts are still optimal for future power systems. We
present a methodology that allows the automated calculation and comparison of
target grids within different concepts. Specifically, we consider radial grids,
closed ring grids and grids with switching stations. A target grid structure is
optimized for each of those grid concepts based on geographical information. To
model a realistic planning process, compliance with technical constraints for
normal operation, contingency behaviour and reliability figures are ensured in
all grid concepts. We present a multiphase approach to solve the optimization
problem based on an iterated local search meta-heuristic. We then economically
compare the grids with regards to CAPEX and OPEX for primary and secondary
equipment, to analyse which concept leads to the most overall cost-efficient
target grids. Since the methodology allows an automated evaluation of a large
number of grids, it can be used to draw general conclusions about the
cost-efficiency of specific concepts. The methodology is applied to 44 real MV
grids spanning about 4800km of lines, for which the results show that a radial
grid structure is overall cost efficient compared to grid topologies with
switching stations or closed rings even in grid areas with a large DG
penetration. The contribution of this paper is threefold: first, a
comprehensive methodology to compile automated target grid plans under
realistic premises is presented. Second, the practical applicability of the
approach is demonstrated with a large scale case study with a high degree of
automation. And third, the results of the case study allow to draw conclusions
about the techno-economical differences of different MV grid concepts.

Computational Engineering, Finance, and Science