PJM extended the Geomagnetic Disturbance Warning it issued the morning of Oct. 10 to 2 p.m. on Oct. 11 while also temporarily issuing a less common GMD Action overnight in response to an increase in intensity of solar activity.
The warning was in effect as of 11:41 a.m. ET Oct. 10 in response to a NERC warning based on a notice from the National Oceanic and Atmospheric Administration (NOAA), the arm of NASA responsible for tracking space weather.
PJM’s warning follows established protocols with members to mitigate any potential disruption to the system from geomagnetically induced currents, or GICs. The warning was upgraded to an action at 7:39 p.m. Thursday to protect the power system from damage or disruptions due to increased GICs.
Space weather forecasters at NOAA’s Space Weather Prediction Center issued a Severe (G4) Geomagnetic Storm Watch for Thursday, Oct. 10, into Friday, Oct. 11. Experts there continue to monitor space weather following a strong X-class solar flare and resulting coronal mass ejection that began in the evening of Oct. 8.
A geomagnetic disturbance (GMD) is caused when the sun emits a stream of charged particles that disturb the Earth’s magnetic field. The resulting electrical currents flow through power system equipment and can cause equipment damage and a disruption of interconnected system operation.
When a GMD is identified, PJM operates the system with more conservative power limits in case the unexpected additional power from the GMD flows on the system. Generation dispatchers may need to follow more restrictive plant procedures to protect equipment, which may result in less power being produced. When conditions warrant, the PJM dispatcher may take action as soon as necessary for a GMD but must take action if conditions persist for 10 minutes.
“We evaluate and monitor geomagnetic activity across our system and proactively position the system for anticipated conditions resulting from the GMDs, if needed,” said Kevin Hatch, Senior Manager – Dispatch.
While severe GMD warnings are not common, lower-level activity has resulted in GMD Alerts from PJM on 10 separate days in 2024, including a warning issued on Oct. 7. GMD Actions are even less common, with only two other instances in the last decade. One of those instances occurred on May 10 of this year, which reflects the period of higher solar activity that the sun is currently in.
The sun is currently in the midst of a solar cycle in which sunspot activity is high. Solar cycles are usually 11 years in length, according to NOAA. The solar maximum of this current cycle is expected in July 2025.
What Is a Geomagnetic Disturbance?
Geomagnetic disturbances (PDF), also known as solar magnetic disturbances, are caused by activity on the surface of the sun. They are fairly rare but pose potential disruptions to the grid.
Sunspots, solar flares or other phenomena can produce large clouds of plasma, called coronal mass ejections. These ejections may induce powerful electric currents within the earth and on high-voltage transmission lines. These currents may flow up from the earth or down into the earth through grounded grid equipment, usually transformers. High levels of these currents have the potential to disrupt or damage transmission equipment.
For example, in March 1989, a major disturbance caused a nine-hour blackout in Quebec and severely damaged a Salem Nuclear Power Plant transformer in Salem County, New Jersey.
Serious impacts from GMD events are rare. The last time PJM was actually impacted by a GMD event was September of 2014.
How Does PJM Help Protect Against Geomagnetic Disturbances?
When the NOAA Space Weather Prediction Center issues an alert to PJM rated above a certain threshold, PJM issues a warning to generation and transmission operators to prepare for potential impacts to equipment.
To help anticipate problems, PJM members have installed special equipment to detect and measure ground-induced currents caused by GMDs. PJM monitors the installed detectors at various locations.
If sustained ground currents at a certain level are detected, PJM operates the system in a more conservative mode until the space weather event has ended.
Emergency procedures can be found on PJM.com and on the PJM Now app.
Original Story (Oct. 10): PJM Issues Geomagnetic Disturbance Warning
PJM issued a warning Oct. 10 that a possible geomagnetic disturbance (GMD) could impact the PJM system through 2 a.m. on Oct. 11.
The warning was in effect as of 11:41 a.m. ET Oct. 10 in response to a NERC warning based on a notice from the National Oceanic and Atmospheric Administration (NOAA), the arm of NASA responsible for tracking space weather. PJM’s warning follows established protocols with members to mitigate any potential disruption to the system from geomagnetically induced currents, or GICs.
PJM does not expect major impacts to the system at this time.
Space weather forecasters at NOAA’s Space Weather Prediction Center issued a Severe (G4) Geomagnetic Storm Watch for Thursday, Oct. 10, into Friday, Oct. 11. Experts there are monitoring the sun following a strong X-class solar flare and resulting coronal mass ejection that began in the evening of Oct. 8.
While severe GMD warnings are not common, lower-level activity has resulted in GMD Alerts from PJM on 10 separate days in 2024, including a warning issued on Oct. 7.
PJM does not anticipate any significant impacts or emergency conditions at this time. PJM is monitoring GMD activity and is in close coordination with generation and transmission owners and neighboring grid operators. No action is required from the public.
PJM GMD warnings alert PJM generation and transmission operators of prescribed operations steps to take to offset possible impacts of such phenomena.
When a GMD is identified, PJM issues a GMD Action and operates the system with more conservative power limits, in case the unexpected additional power from the GMD flows onto the system.
What Is a Geomagnetic Disturbance?
Geomagnetic disturbances (PDF), also known as solar magnetic disturbances, are caused by activity on the surface of the sun. They are fairly rare but pose potential disruptions to the grid.
Sunspots, solar flares or other phenomena can produce large clouds of plasma, called coronal mass ejections. These ejections may induce powerful electric currents within the earth and on high-voltage transmission lines. These currents may flow up from the earth or down into the earth through grounded grid equipment, usually transformers. High levels of these currents have the potential to disrupt or damage transmission equipment.
For example, in March 1989 a major disturbance caused a nine-hour blackout in Quebec and severely damaged a Salem Nuclear Power Plant transformer in Salem County, New Jersey.
Serious impacts from GMD events are rare. The last time PJM was actually impacted by a GMD event was September of 2014.
How Does PJM Help Protect Against Geomagnetic Disturbances?
When the NOAA Space Weather Prediction Center issues an alert to PJM rated above a certain threshold, PJM issues a warning to generation and transmission operators to prepare for potential impacts to equipment.
To help anticipate problems, PJM members have installed special equipment to detect and measure ground-induced currents caused by GMDs. PJM monitors the installed detectors at various locations.
If sustained ground currents at a certain level are detected, PJM operates the system in a more conservative mode until the space weather event has ended.