Geomagnetically induced currents (GICs), although small in magnitude, can inflict detrimental effects on power systems. GICs damage transformers, generate unusual harmonics, trip reactive power support equipment, cause protective relays to malfunction, and may even collapse the entire power system if not mitigated. This paper studies the adverse effects of the negative-sequence harmonics produced by GICs flowing in power transformers. Our simulations show that a transformer's susceptibility to GIC depends on core type, voltage level, associated harmonics order, and GIC magnitude. High-voltage and extra-high-voltage tests were carried out in SIMULINK. GIC was also emulated experimentally to validate the simulated excitation current and harmonics produced by the GIC. The simulation and experimental results show that the 2nd and the 5th harmonics are the most prominent harmonics associated with GIC and dc saturation. Even if a transformer is ungrounded, the negative-sequence harmonics produced by the GIC can still propagate through a transformer and cause harmful effects on the isolated side.

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地磁感应电流（GIC）虽然幅度很小，但会对电力系统造成有害影响。 GIC 会损坏变压器，产生异常谐波，使无功功率支持设备跳闸，导致保护继电器故障，如果不加以缓解，甚至可能导致整个电力系统崩溃。本文研究了电力变压器中流动的GIC产生的负序谐波的不利影响。我们的模拟表明，变压器对 GIC 的敏感性取决于磁芯类型、电压水平、相关谐波次数和 GIC 幅度。高压和超高压测试在SIMULINK中进行。还对 GIC 进行了实验仿真，以验证 GIC 产生的模拟励磁电流和谐波。仿真和实验结果表明，2 次和 5 次谐波是与 GIC 和直流饱和相关的最突出的谐波。即使变压器不接地，GIC产生的负序谐波仍然可以通过变压器传播并对隔离侧造成有害影响。