To conclude, current development trends clearly point to polymer-housed arresters at
all voltage levels. At medium voltages, the process is more or less complete. At the high
and extra-high voltage levels, these changes will take more time because the investment
costs are higher and the acceptance of new technologies is generally lower (due to the
higher risks). However, even in this area, the proportion of polymer-housed arresters is
growing at the expense of porcelain housings, thanks to the obvious cost and technology
benefits.