IEEE Electrification Magazine - December 2015 - 37

NOAA Space Weather Scales

Category

Effect

Scale Descriptor

Physical
Measure

Average
Frequency
(One cycle =
11 years)

K values*
determined
every
3h

Number of
storm events
when K level
was met,
(number of
storm days)

Duration of Event Will Influence Severity of Effects

Geomagnetic Storms

G5

Extreme

Power systems: widespread voltage control problems and protective
system problems can occur, some grid systems may experience complete
collapse or blackouts. Transformers may experience damage.
Spacecraft operations: may experience extensive surface charging,
problems with orientation, uplink/downlink, and tracking satellites.
Other systems: pipeline currents can reach hundreds of amps, (high
frequency) HF radio propagation may be impossible in many areas for one to
two days, satellite navigation may be degraded for days, low-frequency radio
navigation can be out for hours, and aurora has been seen as low as Florida
and southern Texas (typically 40° geomagnetic latitude).**

K=9

Four per cycle
(Four days
per cycle)

G4

Serve

Power systems: possible widespread voltage control problems and
some protective systems will mistakenly trip out key assets from the grid.
Spacecraft operations: may experience surface charging and tracking
problems, corrections may be needed for orientation problems.
Other systems: induced pipeline currents affect preventive measures,
HF radio propagation sporadic, satellite navigation degraded for hours,
low-frequency radio navigation disrupted, and aurora has been seen as
low as Alabama and northern California (typically 45° geomagnetic latitude).**

K=8

100 per cycle
(60 days per
cycle)

G3

Strong

Power systems: voltage corrections may be required, false alarms
triggered on some protection devices.
Spacecraft operations: surface charging may occur on satellite components,
drag may increase on low-Earth-orbit satellites, and corrections may be
needed for orientation problems.
Other systems: intermittent satellite navigation and low-frequency radio
navigation problems may occur. HF radio may be intermittent, and aurora has
been seen as low as Illinois and Oregon (typically 50° geomagnetic latitude).**

K=7

200 per cycle
(130 days per
cycle)

G2

Moderate

Power systems: high-latitude power system may experience voltage
alarms, long-duration storms may cause transformer damage.
Spacecraft operations: corrective actions to orientation may be required
by ground control; possible changes in drag affect orbit predictions.
Other systems: HF radio propagation can fade at higher latitudes, and aurora
has been seen as low as New York and Idaho (typically 55° geomagnetic latitude).**

K=6

600 per cycle
(360 days per
cycle)

G1

Minor

Power systems: weak power grid fluctuations can occur.
Spacecraft operations: minor impact on satellite operations possible.
Other systems: migratory animals are affected at this and higher levels;
aurora is commonly visible at high latitudes (northern Michigan and Maine).**

K=5

1,700 per
cycle
(900 days per
cycle)

** Based on this measure, but other physical measures are also considered.
Figure 3. The NOAA geomagnetic storm G-scale. (Source: NOAA.)

DVP has a dedicated team that evaluates field-operations concerns and performs research associated
with GIC and GMD issues. Like many long-term R&D
projects that have been executed at DVP, technical
works such as methodical studies, field testing, and
event analysis are performed, which ultimately provide theoretical and practical support to leverage the
company's operation and management. The outcome

is applied into the design process and operational procedures, which can benefit the company's core businesses. DVP has developed a GMD mitigation plan
(Figure 2) that consists of three major pillars: situational awareness, equipment enhancement, and geoelectric scenario studies and modeling. Best practices and
methodologies have been shared at different industry
forums, including those sponsored by the Department
	

IEEE Elec trific ation Magazine / d ec em be r 2 0 1 5

37



Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2015

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