Toward Dielectric Scaling Laws for Mixed Voltage Waveforms: Surface Flashover for Sine and Pulse Excitations with DC Offsets

Modern naval power systems increasingly employ medium-voltage architectures featuring both sinusoidal and pulsed waveforms, often overlaid with DC offsets for advanced propulsion and medium-voltage power distribution [1]. These non-traditional voltage profiles challenge existing creepage and clearance (C&C) guidelines, which were developed primarily for $50 / 60 ~\text{Hz}$ sinusoidal operation [2], [3]. In this paper, we examine surface flashover inception in a controlled setup where 60 Hz sinusoidal and pulse signals, each with zero, positive, or negative DC offsets, are applied to an aluminum electrode atop a Flameretardant Polyvinyl Chloride (FPVC) insulator. The test voltage amplitude is held at approximately 6 kV peak-to-peak, allowing the comparison of different offset polarities while maintaining an equivalent stress level. Results reveal that negative DC offsets systematically increase the flashover threshold for both waveform types, suggesting that negative-shifted potential profiles may redistribute electric fields in a manner that delays partial discharge (PD) or streamer formation. Conversely, positive offsets and purely AC conditions yield notably lower flashover thresholds, indicating potential underestimation of insulation requirements in scenarios where waveform polarity or offset levels deviate from standard AC assumptions. Looking ahead, we propose a novel four-sided, adjustable “drawer” architecture to further investigate C&C designs and requirements. This apparatus will house Power Electronic Building Blocks (PEBBs) and inductors, allowing configurable insulation distances and enabling advanced testing under a variety of waveforms, frequencies, and environmental conditions. Ultimately, this research aims to refine dielectric scaling law (DSL) based guidelines for highdensity naval power systems, mitigating insulation failures while minimizing unnecessary design conservatism.