In the UK we have a number of locations which are permanently wired with overhead line, but the wires are permanently earthed. This is typically done where the OCL is out of use in depots (for safety), to pass OCL through a very low bridge where electrical clearances cannot be provided, or at the limit of an electrified line.
Has this been dealt with before? I would propose the following approach: electrified=contact_line voltage=0 frequency=<unset>
