Zone of influence of ground potential rise on wire-line communication installations in urban areas

Wire-line communication installations serving telephone subscribers in the zone of influence of fault-produced ground potential rise (GPR) in an area surrounding the high voltage substations require special protection. In urban areas the substation grounding system may be connected to or located near to a large and complex network of conductors composed of metal sheaths of power and telecommunication cables, pipes for water, gas and heating, and rails of traffic systems, which in some cases might enlarge the GPR zone of influence. This paper presents analysis of the influence of such metal structures external to the substation grounding system on the GPR zone of influence