Challenges in Conducting Risk Assessment and Designing Protection Measures as per IEC 62305 for a Twin Tower of Different Heights

This paper addresses some practical issues at the stages of conducting the risk assessment and designing the external lightning protection system according to the IEC 62305 standards, for a twin-tower building. In a building complex of multiple structures, a significant difference in material and installation cost could be resulted depending on the fact that the complex is considered as a single building or several individual buildings. The standards do not specify a solid criterion for determining whether several adjacent buildings are considered as a single entity or multiple structures. The same issue may give rise to a strategically problematic scenario in designing the air-termination system for tall twin structures with different heights as IEC 62305–3 (2010) standards prescribe air-termination network down to 80% of the height of the building from the rooftop level, for buildings of height more than 60 m. The paper proposes a rational solution for overcoming the undetermined specifications pertinent to these cases.