Electricity + Control October 2017

round up

EARTHING + LIGHTNING PROTECTION

Solar plants – managing the lightning risk

conditions such as poor soil resistivities; and with the extended and interconnected nature of these plants, add to the challeng- es presented in respect of ground potential rises and differential voltages across the site and between elements, and conse- quent risks to the interconnected systems and equipment. Plant equipment is relatively exposed to both direct strikes and to the induced ef- fects of the electromagnetic fields associ- ated with lightning strikes. These fields can potentially affect and damage buried servic- es (such as cables) as well as above-ground equipment. The damage to buried services (such as insulation damage) can potentially become apparent only at a later stage (‘la- tent damage’). Whilst plants of this nature might not be extensively manned, this can vary during different times (for example during construction and maintenance) and the risks associated with injury must still be carefully considered, in addition to the risk

of economic loss. The nature of such plants and the associated risks emphasise the need for an effective, holistic lightning pro- tection solution that is coherent across all aspects. Important aspects and elements of such a solution include, for example, di- rect strike protection, site-wide equipoten- tialisation, and the careful, considered and consistent definition and application of light- ning protection zones (and of their boundary management) – the latter includes the ap- propriate and coherent application of surge protection as well as appropriate cabling practices (including shielding). Enquiries:Tel. +27 (0) 12 663 4804 or email ianmac@engenamic.com

Solar plants, particularly (but certainly not only) large facilities such as utility-scale PV plants, present particular challenges in re- spect of lightning protection. Engenamic CEO and principal advisor/consultant Ian McKechnie says that there are particular general characteristics of such sites and applications that contribute to their expo- sure and vulnerability to the deleterious ef- fects of lightning. He says, “They present a complex site and application environment, and this complexity impacts directly on the broad-based risks and engineering (and oth- er) management challenges associated with lightning safety and lightning protection”. These are typically large and geograph- ically extended sites, with factors such as the extensive interconnected electrical and electronic equipment and system elements adding to the complexity and challenges to be addressed and managed in a holistic and integrated manner. Often these sites are located in areas with difficult grounding