Designing building structures for protection against EMP and lightning

This article will explore the use of electromagnetic simulation when hardening facilities against EMP and lightning. EMP is a high-intensity burst of electromagnetic energy that can potentially cause major disruption to vital infrastructure such as telecommunications, electrical power, banking and finance, emergency services, medical facilities, transportation, food and water supply. Lightning can cause significant damage by directly striking a building, when metallic structures such as electrical wiring provide return current flow in an attempt to equalize potentials. It is therefore essential to protect or “harden” critical facilities by stringent electromagnetic design, including shielding to block incident EMP fields, careful treatment of points of entry (POE) and diversion of lightning currents using down-conductors. This article shows how a simulation of the performance of EMP protection measures at the point of entry, such as filtering and clamping, can be set up and carried out. The simulation of a lightning strike to a building structure is also demonstrated, to show how the induced current return paths can be visualized in order to characterize the possible effect of the lightning strike on systems inside the building. This includes an investigation of cable system positioning inside the building and the prediction of induced shield and internal load currents and the analysis of lightning protection system (LPS), taking into account the effect of down-conductor type and grounding impedance.