Geomagnetically induced currents (GICs) during a space weather event have previously caused transformer damage in New Zealand. During the 2015 St. Patrick's Day Storm, Transpower NZ Ltd has reliable GIC measurements at 23 different transformers across New Zealand's South Island. These observed GICs show large variability, spatially and within a substation. We compare these GICs with those calculated from a modeled geolectric field using a network model of the transmission network with industry‐provided line, earthing, and transformer resistances. We calculate the modeled geoelectric field from the spectra of magnetic field variations interpolated from measurements during this storm and ground conductance using a thin‐sheet model. Modeled and observed GIC spectra are similar, and coherence exceeds the 95% confidence threshold, for most valid frequencies at 18 of the 23 transformers. Sensitivity analysis shows that modeled GICs are most sensitive to variation in magnetic field input, followed by the variation in land conductivity. The assumption that transmission lines follow straight lines or getting the network resistances exactly right is less significant. Comparing modeled and measured GIC time series highlights that this modeling approach is useful for reconstructing the timing, duration, and relative magnitude of GIC peaks during sudden commencement and substorms. However, the model significantly underestimates the magnitude of these peaks, even for a transformer with good spectral match. This is because of the limited range of frequencies for which the thin‐sheet model is valid and severely limits the usefulness of this modeling approach for accurate prediction of peak GICs.

中文翻译：

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新西兰南岛的地磁感应电流模型验证

太空天气事件期间的地磁感应电流（GIC）以前曾在新西兰造成变压器损坏。在2015年圣帕特里克节暴风雨期间，Transpower NZ Ltd在新西兰南岛的23个不同变压器上进行了可靠的GIC测量。这些观测到的GIC在变电站中的空间和空间上显示出很大的可变性。我们将这些GIC与使用具有行业提供的线路，接地和变压器电阻的传输网络的网络模型从建模的地电领域计算出的GIC进行比较。我们使用薄板模型从风暴和地面电导期间的测量值内插的磁场变化谱中计算出模拟的地电场。建模和观察到的GIC光谱相似，相干性超过95％的置信度阈值，对于23个变压器中的18个最有效的频率。敏感性分析表明，建模的GIC对磁场输入的变化最敏感，其次是对陆地电导率的变化。传输线遵循直线或使网络电阻完全正确的假设意义不大。比较已建模和已测量的GIC时间序列可以看出，该建模方法可用于在突然开始和亚暴期间重建GIC峰值的时间，持续时间和相对幅度。但是，即使对于具有良好光谱匹配的变压器，该模型也大大低估了这些峰值的幅度。