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27 Nov 2020, 12:34
Kudos
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A space weather event can produce geomagnetically induced currents (GICs) that may be transmitted by surface-connected conductors such as the electric-power grid. When GICs enter the power grid, they act as direct current (DC) sources that flow alongside the normal alternating currents (AC) produced at power plants and transferred along power lines to electrical substations. Basic incompatibilities between DC and AC currents may interfere with the normal functioning and performance of Extra High Voltage (EHV) transformers. The interaction of GICs with these transformers can result in a number of physical effects that, if sufficiently large and not properly managed, may adversely impact the power system.
For example, GIC–transformer interactions can increase reactive power consumption, contributing to voltage instabilities and potentially leading to power outages. They can also cause interference that leads to the improper operation of protective relay equipment (e.g., static compensators) and/or the tripping offline and potentially damaging of generators. It is important to note that this impact pathway is the only one that has to-date been known to trigger space weather–related blackouts.
For example, GIC–transformer interactions can increase reactive power consumption, contributing to voltage instabilities and potentially leading to power outages. They can also cause interference that leads to the improper operation of protective relay equipment (e.g., static compensators) and/or the tripping offline and potentially damaging of generators. It is important to note that this impact pathway is the only one that has to-date been known to trigger space weather–related blackouts.
For each of the following, select Inferred if the statement can be reasonably inferred from the information provided. Otherwise, select Not Inferred.
| Inferred | Not Inferred | |
| Emergency procedures may be needed during both moderate and extreme space weather events. | ||
| Both direct current and alternating current can flow through the electric-power grid to Extra High Voltage transformers. | ||
| Extra High Voltage transformers are vulnerable to disruption during space weather events. |
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Official Answer
Emergency procedures may be needed during both moderate and extreme space weather events.: Not Inferred
Both direct current and alternating current can flow through the electric-power grid to Extra High Voltage transformers.: Inferred
Extra High Voltage transformers are vulnerable to disruption during space weather events.: Inferred
27 Nov 2020, 12:34
Kudos
Bookmarks
Official Solution:
Mitigating actions may be needed during both moderate and extreme space weather events.
• In Tab 2, “emergency procedures” appear only in italic text, which the tab explains corresponds to extreme storms. There are no examples of emergency procedures listed in regular text, so it cannot be inferred that such actions may be needed during both storm types. Not Inferred.
Both direct current and alternating current can flow through the electric-power grid to Extra High Voltage transformers.
• Tab 1 states that GICs (which are DC) enter the grid and flow alongside AC toward substations and transformers. So it can be inferred that both DC and AC can flow through the grid to EHV transformers, even if the DC flow is unintended and disruptive. Inferred.
Extra High Voltage transformers are vulnerable to disruption during space weather events.
• Tab 1 states that geomagnetically induced currents may interfere with the normal functioning and performance of Extra High Voltage transformers. This supports the inference that such transformers are vulnerable to disruption during space weather events. Inferred.
Correct answer:
Emergency procedures may be needed during both moderate and extreme space weather events. "Not Inferred"
Both direct current and alternating current can flow through the electric-power grid to Extra High Voltage transformers. "Inferred"
Extra High Voltage transformers are vulnerable to disruption during space weather events. "Inferred"
Bunuel
Mitigating actions may be needed during both moderate and extreme space weather events.
• In Tab 2, “emergency procedures” appear only in italic text, which the tab explains corresponds to extreme storms. There are no examples of emergency procedures listed in regular text, so it cannot be inferred that such actions may be needed during both storm types. Not Inferred.
Both direct current and alternating current can flow through the electric-power grid to Extra High Voltage transformers.
• Tab 1 states that GICs (which are DC) enter the grid and flow alongside AC toward substations and transformers. So it can be inferred that both DC and AC can flow through the grid to EHV transformers, even if the DC flow is unintended and disruptive. Inferred.
Extra High Voltage transformers are vulnerable to disruption during space weather events.
• Tab 1 states that geomagnetically induced currents may interfere with the normal functioning and performance of Extra High Voltage transformers. This supports the inference that such transformers are vulnerable to disruption during space weather events. Inferred.
Correct answer:
Emergency procedures may be needed during both moderate and extreme space weather events. "Not Inferred"
Both direct current and alternating current can flow through the electric-power grid to Extra High Voltage transformers. "Inferred"
Extra High Voltage transformers are vulnerable to disruption during space weather events. "Inferred"
