Ground Rise Potential (GRP) occurs in every instance in which an earthed network becomes ENERGISED.
The extent and effect of GRP may vary from day to day, hour to hour, minute to minute. A safe site in the morning maybe a dangerous site in the afternoon.
An earthed network is not a dead network. It may become energised from numerous.uncontrollable sources, including lightning strike, induced voltage, earth fault on another line and “accidental switch on” which is not supposed to happen but records prove otherwise. All of the above energy sources will cause Ground Rise Potential.
Accidental contact with live overhead conductors by a Crane, Mechanical Excavator or their loads will create the same Danger Zone as the driven earth rod above.