Radiated and conducted research on damage characteristics of digital protective relays in substations under high-altitude electromagnetic pulse environment.

This article investigates the damage characteristics of digital protective relays (DPRs) in substations subjected to high-altitude electromagnetic pulse (HEMP) environments through both radiated and conducted tests. Three representative DPR circuits—the current transformer (CT) circuit, gas protection circuit, and power supply circuit—were examined to determine port coupling behaviors and vulnerability. Results indicate that the current acquisition port and power supply port possess effective surge protective devices that suppress surge voltage peaks and widths, enabling them to withstand maximum radiated field intensities (50 kV/m) and injection voltages (up to 50 kV) without damage. Conversely, the gas protection port lacks adequate surge protection, leading to linear increases in surge voltage peaks and resulting in irrecoverable damage at 50 kV/m radiated field intensity and injection voltages of 20–30 kV. The study highlights the complementary roles of radiated and conducted testing in assessing DPR vulnerability and provides insights for enhancing substation equipment protection and overall power system stability.