Medium voltage (MV) overhead lines (OHL) are an
inseparable part of distribution grids in most countries. The
relative importance of OHL is larger in rural areas, where
consumers are scattered and the relative number of consumers
supplied by one line is small. In this case, using underground
cable lines (UGC) is not practical due to disproportionately
high building expenses. Therefore it is reasonable to use OHL
in these areas also in the future. The Estonian distribution grid
is a fine example of a distribution grid in which the proportion
of OHL is large. Presently, the distribution grid of Estonian
consists of nearly 80% OHL and 20% UGC.