High-voltage station arresters are usually not directly earthed; instead monitoring devices,
such as surge counters, monitoring spark gaps or leakage current indicators are
connected with the arrester in series. In this case insulation is provided for by setting the arrester up on insulating feet (Figure 13). Earthing then occurs through the appropriate
monitoring devices. The insulating feet must be mechanically designed in such a way,
that they can withstand long-term as well as short-term mechanical forces affecting the
arrester. They must have adequate electrical strength, so that they do not flashover under
the stress of the voltage drops across the monitoring devices situated in parallel and
caused by the self-inductance of the ground connection