Abstract
Although the probability of a phase to ground fault occurring at a specific transmission powerline tower and resulting in an arc to an adjacent pipeline may be quite small, the risk cannot be ignored due to the severity of the potential consequences. A sustained arc to a pipeline could result in melting of the pipe wall and catastrophic failure of the pipeline. Additionally, the powerline fault current would be trans
ferred directly to the pipeline via the arc, resulting in safety risks, the potential for additional arcing risks at crossings with foreign structures, and a risk of damage to isolating flanges and to cathodic protection equipment upstream and downstream of the fault location.
In order to ensure there is no risk of arcing, a critical or “safe” separation distance between the pipeline and any part of the powerline tower foundation or grounding system must be maintained. This paper discusses how to determine the critical separation distance that is required to avoid an arc based on research, literature and standards, and explores mitigation options in circumstances where this distance cannot be feasibly maintained. Calculations and mitigation measures from a case study and a pilot site will be presented.
