  Network models of large-scale electricity systems feature only a limited
spatial resolution, either due to lack of data or in order to reduce the
complexity of the problem with respect to numerical calculations. In such
cases, both the network topology, the load and the generation patterns below a
given spatial scale are aggregated into representative nodes. This
coarse-graining affects power flows and thus the resulting transmission needs
of the system. We derive analytical scaling laws for measures of network
transmission capacity and cost in coarse-grained renewable electricity
networks. For the cost measure only a very weak scaling with the spatial
resolution of the system is found. The analytical results are shown to describe
the scaling of the transmission infrastructure measures for a simplified, but
data-driven and spatially detailed model of the European electricity system
with a high share of fluctuating renewable generation.
