TABLE 5.1 Geomagnetic Storm Intensity and K Index Value

GIC Severity Level

XFMRa Neutral DC Current

Corresponding Geomagnetic Storm Index



5-14 amps




15-29 amps




30-59 amps




>60 amps


aXFMR, transformer. Shown in Figure 5.4 is an example of a high-voltage electrical power transformer damaged by GICs.

grids are located at higher geomagnetic latitudes, which are more strongly affected by geomagnetic storms. As a consequence, the magnetic disturbances at higher latitudes reach higher K levels before those at the lower-latitude stations. A general feature of geomagnetic storms is that their timing and intensity are a local phenomenon, and the best real-time data come from geomagnetic field monitoring equipment located closest to the end user of the data. As a result, system operators at higher latitudes utilize higher-latitude sources of magnetic disturbance data in addition to the NOAA SWPC and combine those data with real-time ground-current monitoring throughout their grid. These other third-party (often commercial) sources of geomagnetic data also add to the real-time data some interpretation and forecasting that are of value to electric power system operators.

In addition to real-time space weather monitoring, high-reliability near-term forecasts are critical to power system operators. Advance warning about the arrival of an earthward-directed CME is of critical importance for grid operators, allowing them time to take the measures needed to protect the grid. “The most important device that I know of out there to give us a heads-up is ACE,” McGovern noted. “ACE gives our operators about a 45-minute warning.” As Frank Koza said earlier, “We can reposition our system in probably up to 15 minutes. With 15 minutes’ advance notice we can quick-start units, reducing generation in the northern areas, picking up generation in the southern areas, offloading our tie lines, offloading our transformers, even manning key facilities so that we have operators there to switch off a transformer if they see the temperature on that transformer overloading.” And, “for the real-time operator, 45 minutes to an hour is very important. I would give it a 10 (on a scale of 1 to 10). That would be the same for the day-ahead market, which is at least 24 hours out.”


Precision geo-location services based on GPS signals arose almost simultaneously with the birth of the GPS system more than 20 years ago (see Box 5.2). Precision geo-location is critical to many users (see Figure 5.6) including,

  • Oil and gas companies,

  • Agriculture,

  • Mining,

  • Construction contractors, and

  • Government agencies,

as part of their operations performing,

  • Seismic navigation,

  • Dynamic and static rig positioning,

  • Dredging control,

  • Vessel and vehicle tracking,

  • Photogrammetry and geographic registration, and

  • Position confirmation and attitude monitoring using GPS kinematic solutions.

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