What size conductors should I use? And, is there a simple table I can use for this high voltage earthing design? These are great questions that I'm often asked. This post answers these questions together with the choice of conductor materials and jointing method within a high voltage earthing design project. Assessing conductor size is entirely dependent on the electrical configuration and the load that the conductor must take. For example, an above-ground bonding conductor serves to transfer current with minimal voltage drop, from A to B. A directly buried conductor has an additional purpose, that of leaking the fault current/voltage into the local geology (as part of an electrode). When considering Lightning, the same conductor above might also see a high-frequency component and which will impose yet another requirement.