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Abstract
The performance of surge arresters in high-voltage substations is strongly influenced by the configuration of their downlead conductors, particularly under lightning impulse conditions. International standards recommend that downleads should be as short and straight as possible; however, practical installation constraints often require bends and deviations. This paper investigates the effect of downlead curvature and bending angles on the transient voltage distribution of surge arresters using the Current Distribution, Electromagnetic Interference, Grounding and Soil Structure Analysis (CDEGS) software. A 1.2/50 μs, 10 kA lightning current impulse was injected at the top of a 2.4 m copper downlead connected to a realistic grounding grid embedded in a two-layer soil model. Four configurations were analysed: a straight downlead, a single elbow bend, two elbow bends, and a combined elbow–saddle bend, with bending angles of 10°, 45°, and 90°. The computed results demonstrate that increasing the number and severity of bends leads to significant voltage rises along the downlead, with peak voltage differences exceeding 30 kV for 90° configurations. Additional analytical and numerical evaluations of resistance and inductance confirm that increased curvature introduces higher inductive effects, contributing to the observed voltage amplification. The findings highlight the critical impact of downlead geometry on surge arrester performance and provide quantitative guidance for substation design practices to minimise transient overvoltages and enhance insulation coordination.