A high-altitude electromagnetic pulse (HEMP) may pose a significant threat to the electrical power grid. In this context, the present study considers the potential impact of the HEMP early-time component (E1) on the winding of a typical transmission power line transformer. A time-domain, fully electromagnetic, three-dimensional, finite-element model was used to simulate the propagation of an E1-induced voltage surge into the transformer winding. The analysis is focused on the first few turns of the winding, the ones that are impacted by the largest electric field resulting from the applied pulse. The model follows the transient dynamics, while the pulse is traveling along the conductor, and the electric field is established across the insulation gaps through capacitive coupling. The simulations also considered the effect of an electrically floating, “shield” winding conductor. This is used as a countermeasure to improve the voltage uniformity across the winding during fast-rise transients. In this case, the propagation of the E1-induced pulse is compared with that from a slower rising, lightning standard waveform. The simulation results show that the presence of the shield conductor can effectively reduce the peak electric field between winding turns, in the presence of either E1 or lightning waveforms.

中文翻译：

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大功率变压器绕组中快速上升瞬变的仿真

高空电磁脉冲 (HEMP) 可能对电网构成重大威胁。在这种情况下，本研究考虑了 HEMP 早期分量 (E1) 对典型输电线路变压器绕组的潜在影响。时域、全电磁、三维、有限元模型用于模拟 E1 感应电压浪涌传播到变压器绕组中。分析集中在绕组的前几匝，即受到施加脉冲产生的最大电场影响的匝。该模型遵循瞬态动力学，脉冲沿导体传播，电场通过电容耦合跨越绝缘间隙建立。模拟还考虑了电浮动、“屏蔽”绕组导体的影响。这被用作在快速上升瞬变期间改善绕组两端电压均匀性的对策。在这种情况下，将 E1 感应脉冲的传播与上升较慢的闪电标准波形的传播进行比较。仿真结果表明，在存在 E1 或雷电波形的情况下，屏蔽导体的存在可以有效地降低绕组匝间的峰值电场。