Geomagnetically induced currents (GICs) in the North Island New Zealand power transmission network during two large magnetic storms are calculated from both magnetotelluric (MT) data and a thin‐sheet conductance model of New Zealand previously used to study GIC in the South Island. We focus on the 2015 St. Patrick's Day magnetic storm and the storm of 20 November 2003. Lack of MT data in the northwestern part of the Island means that the transmission network in this region is represented by an equivalent circuit. Lack of GIC observations in the North Island means that results cannot be directly compared with measured GIC. However, our calculation of GIC shows that substations and individual transformers in the lower part of the Island with significant currents are generally the same as those where total harmonic distortion has been observed during periods of enhanced geomagnetic activity. MT data in the period range 2–30 min are used to predict GIC associated with the sudden storm commencement and rapid variations in the magnetic field. In contrast, the thin‐sheet modeling approach shows that GIC may be expected to occur in conjunction with longer‐period variations. Calculations for the 2003 storm suggest that at some locations GIC in excess of 10 A may persist for long periods of time and may produce significant harmonic distortion which could lead to localized transformer heating. It is concluded that despite its relatively low latitude the North Island power network is potentially at risk from significant GIC during extreme storms.

中文翻译：

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使用MT数据和薄板模型计算新西兰北岛的GIC

根据大地电磁（MT）数据和先前用于研究南岛GIC的新西兰薄电导模型，计算出两次北风新西兰大岛输电网络中的地磁感应电流（GIC）。我们将重点放在2015年的圣帕特里克节电磁风暴和2003年11月20日的风暴上。该岛西北部缺少MT数据，这意味着该地区的传输网络由等效电路表示。在北岛缺乏GIC观测资料意味着无法将结果与测得的GIC直接进行比较。然而，我们对GIC的计算表明，在岛下部的变电站和单个变压器中，有大量电流通常与在增强的地磁活动期间观测到总谐波失真的那些相同。2-30分钟范围内的MT数据可用于预测与暴风雨的突然爆发和磁场的快速变化相关的GIC。相比之下，薄板建模方法表明GIC可能会与更长时期的变化一起发生。2003年风暴的计算表明，在某些位置，超过10 A的GIC可能会持续很长时间，并且可能会产生明显的谐波失真，从而可能导致变压器局部发热。