On Lightning Ground Potential Rise and Wire- Line Communications in Large Utility Scale PV Plant

IEEE Std 1692 (2011) states that one of the categories that cover electrical equipment damage from lightning is lack of protection against ground potential rise. In the experience of the author, the threat of lightning ground potential rise to sensitive electronic equipment, appears to be overlooked in many cases, particularly in the case of some large utility scale photovoltaic plant. It is worth noting that the concept of earth potential rise or ground potential rise is not mentioned once in the nearly 400 odd pages of the 4 Part IEC 62305 lightning protection standard. In this paper, i) specific comments are raised about anticipated lightning ground potential rise levels and ground potential difference levels, in the context of large utility scale photovoltaic plant; ii) awareness is raised about lightning ground potential rise (GPR) and its threat to sensitive electronic communication equipment, particularly in large utility scale PV plant and iii) the recommendation is made to include an Addendum, making reference to lightning ground potential rise, in the next addition of the IEC 62305 standard. The paper also points out the implication of introducing surge protective devices (SPDs) to wire-line communication systems, such as, an RS 485 system. In such cases, reverse operation of the SPDs under lightning GPR, may result in extended damage. The latter is particularly important to large utility scale PV plant in view of the high number of components present at these locations.