The electric transmission system needs more protections against geomagnetic disturbances like the 1989 solar storm that caused the collapse of the Hydro-Quebec grid, the Federal Energy Regulatory Commission said last week.
In its Final Rule on a Notice of Proposed Rulemaking issued last October (RM12-22), the commission ordered the North American Electric Reliability Corp. (NERC) to issue standards to close the “reliability gap” regarding geomagnetic disturbances (GMDs) caused by solar events.
GMDs caused by solar events can cause distortions in the earth’s magnetic field, affecting the operations of pipelines and communications systems as well as electric power systems. Geomagnetically induced currents (GICs) can enter the transmission system, flowing through transformers and transmission lines and leading to increased reactive power consumption and disruptive harmonics that can cause system collapse.
The commission ordered NERC to propose reliability standards in two stages. Stage one standards will mandate operational procedures to mitigate the effect of GMDs. PJM already has GMD operational procedures in place (see below).
A Sense of Urgency
The stage one standards must be submitted for FERC review within about eight months (six months from the effective date of the order, which takes effect 60 days after publication in the Federal Register).
The short deadline underscores the urgency regulators place on preparing for GMDs. The current 11-year solar activity cycle is expected to hit its maximum activity in June. Large solar events often occur within four years of such a cycle maximum, panelists told FERC at a technical conference last year.
In stage two, due within 18 months, NERC must determine what severity GMD will constitute a “benchmark” GMD event. Transmission and generator owners and operators will be required to assess the potential impact of such benchmark events on their equipment and systems.
The severity of GMDs are affected by variables including the strength of the solar event; geology, which affects ground conductivity, and the orientation and length of the transmission lines. If a responsible entity finds no potential GMD impacts in its vulnerability assessment, no additional plan is required.
Entities that are vulnerable will be required to implement protections against “instability, uncontrolled separation, or cascading failures” from such events. Such plans cannot be limited to operational procedures or enhanced training, FERC said.
“These strategies could, for example, include automatically blocking geomagnetically induced currents from entering the Bulk-Power System, instituting specification requirements for new equipment, inventory management, isolating certain equipment that is not cost effective to retrofit, or a combination thereof,” FERC wrote. The commission said it was not ordering NERC to require the use of automatic blocking devices or any specific technology.
Disagreement over Worst-Case Scenario
FERC acknowledged it was acting despite a lack of consensus on the severity of the threat. Some comments on the NOPR supported NERC’s 2012 interim GMD report, which predicted that the worst-case GMD scenario is “voltage instability and subsequent voltage collapse.” Others took side with reports issued in 2010 by the Oak Ridge National Laboratory, which concluded that a severe GMD event could damage or destroy transformers.
FERC said the rule “is warranted by even the lesser consequence of a projected widespread blackout without long-term, significant damage to the Bulk-Power System.”
The National Academy of Sciences estimated in 2008 that the most extreme solar event could cost more than $1 trillion and require four to 10 years to recover, while the cost of installing protective equipment was estimated at less than 20 cents per year for an average residential customer.
Oak Ridge’s simulation of a 1 in 100-year geomagnetic storm centered over southern Canada predicted that more than 300 EHV transformers would fail or suffer permanent damage, leading to the collapse of the grids serving 130 million people in the Northeast, Mid-Atlantic and Pacific Northwest.
The 1989 incident started shortly before 3 a.m. EST on March 13, when a large impulse in the geomagnetic field was detected near the U.S.-Canada border. That started a series of disturbances that brought down the grid serving Montreal and the rest of Quebec province within about 90 seconds.
The storm also caused large disturbances in the U.S., damaging some transformers severely — including one at the Salem nuclear plant in New Jersey — and nearly knocking out PJM and transmission systems from New England to the Midwest.
PJM Operating Plans in Place
PJM’s operating plans for dealing with GMDs are detailed in section 3.7 of Manual 13. The plan calls for PJM to notify generation and transmission members via the PJM All-Call system and Emergency Procedure posting application when the National Oceanic and Atmospheric Administration (NOAA) issues an alert for a potential GMD with a ranking of 5 or greater on the 9-point “K-index.”
Once a GMD has been confirmed, PJM dispatchers must operate the system under GMD transfer limits determined from studies that modeled several scenarios, including: loss of the Hydro-Quebec Phase 2 DC line to Sandy Pond; tripping of certain extra high voltage capacitors, and reduction or loss of generation at Artificial Island, the site of the Salem and Hope Creek nuclear plants in New Jersey.
No Guarantees
In its comments in response to the NOPR, PJM said there “is no question that severe space weather has the potential to create serious problems for the Bulk-Power System.” However, PJM and other commenters also asked FERC to clarify that reliability standards cannot eliminate all risks.
The commission agreed: “Given that the scientific understanding of GMDs is still evolving, we recognize that Reliability Standards cannot be expected to protect against all GMD-induced outages.”
