CANCELLED: André Lobato: Modeling and Experimental Assessment of Lightning Attachment and Electrical Discharges

Abstract

Lightning interaction with grounded structures and electrical systems is commonly modeled through partially decoupled steps, from long-gap breakdown parameterization to attachment modeling and network transient analysis. This thesis addresses the resulting lack of methodological coherence by developing a consistent, electric-field-driven leader progression framework in which exposure, attachment, and system-level performance are treated as linked outcomes of a common discharge process. The framework resolves streamer inception, corona charge development, leader inception, propagation, and breakdown and is applied from laboratory long air-gap discharges to power-system interaction.In Part I, the framework quantifies lightning exposure and attachment to grounded structures. For mountaintop towers, self-initiated upward lightning is described through a stabilization-field criterion yielding an effective height controlled by tower-to-mountain slenderness, demonstrating terrain-induced field enhancement governs exposure. For downward lightning to buildings and competing electrodes, attachment is modeled as the interaction between descending stepped leaders and upward connecting leaders, producing geometry- and direction-dependent attractive zones that depart from electrogeometric assumptions. Long air-gap studies show that, in competitive attachment, the final strike point is governed by the coupled timing of streamer activity and upward-leader development rather than geometric clearance.In Part II, the same modeling components are embedded in engineering performance assessment. A probabilistic framework estimates failure rates of transmission lines by combining simulation-based attachment modeling, parameterized return-stroke currents, network transient modeling, and Monte Carlo sampling. Results show that the choice of attachment model influences flash collection rate, current distribution, and outage rate, with differences increasing at higher tower footing impedance. Full-wave simulations of a wave energy converter in seawater show how conductive environments redistribute injected currents and attenuate high-frequency components, highlighting limitations of circuit-based representations.Part III examines the discharge-physics foundations through long air-gap experiments and modeling. Measurements under positive switching impulses show that streamer regions exhibit time-varying geometry and charge content controlled by the local field. Studies of leader propagation confirm that leader velocity is a derived outcome of field and charge-injection conditions, differing between non-overvoltage and overvoltage regimes and between rod–plane and sphere–plane configurations.Overall, the thesis demonstrates that engineering metrics such as effective height, striking distance, attractive radius, return-stroke current representation, and long air-gap parameters emerge from discharge physics, geometry, and environment within a coherent modeling framework. Exposure, attachment, and system-level performance are coupled outcomes of a common electric-field-driven process, providing a basis for assessing when simplified geometric approaches are sufficient and when physics-consistent modeling is required for lightning-resilient infrastructure design.