By Rich Heidorn Jr.

FERC took another step Thursday in its efforts to protect the grid from geomagnetic disturbance events (GMDs), proposing to approve a revised reliability standard but directing NERC to also require mitigation of vulnerabilities to localized events (RM18-8).

The commission’s Notice of Proposed Rulemaking would approve reliability standard TPL-007-2 (Transmission System Planned Performance During Geomagnetic Disturbances), which revises the definition of GMDs, requires grid operators to collect certain data and imposes deadlines for corrective actions, as the commission directed in Order 830 in 2016. (See FERC Approves GMD Reliability Standard.)

GMDs occur when the sun ejects charged particles that cause changes in the earth’s magnetic fields, potentially causing geomagnetically induced currents that can cause voltage instability or collapse and damage connected equipment.

The rule would require planning coordinators and transmission planners to conduct supplemental GMD vulnerability and thermal impact assessments that go beyond NERC’s original “benchmark” GMD event definition that is based on spatially averaged data.

NERC defined the “supplemental” GMD event using individual station measurements rather than spatially averaged measurements, acknowledging that geomagnetic fields during severe GMD events can be “spatially non‐uniform” with localized peaks that could affect reliability.

The supplemental GMD event is defined by a “reference peak geoelectric field amplitude” of 12 V/km versus the 8 V/km used in the original spatially averaged definition. Both are intended to reflect a one-in-100-year occurrence and use scaling factors to account for local geomagnetic latitudes and earth conductivity. They also employ a “locally enhanced reference geomagnetic field time series or waveform” to analyze the impact of the GMD on equipment.

Mitigation Directive

NERC’s standard requires mitigation of vulnerabilities to the benchmark event, setting a one-year deadline for the completion of corrective action plans and two- and four-year deadlines to complete mitigation actions involving non-hardware and hardware mitigation, respectively.

But NERC rebuffed FERC’s call for mitigation of risks from supplemental events. NERC’s proposed standard would only require applicable entities to make “an evaluation of possible actions designed to reduce the likelihood or mitigate the consequences and adverse impacts of the event(s)” if a supplemental GMD event is assessed to result in cascading outages.

NERC told FERC that its standard drafting team determined that requiring corrective action plans in response to supplemental GMD event vulnerabilities was premature because the supplemental definition is based on small number of observed events “that provide only general insight into the geographic size of localized events during severe solar storms.” NERC also said current tools are inadequate to realistically model localized events.

But the commission said NERC’s position ignored its directives in 2013’s Order 779, which were reiterated in Order 830.

“NERC’s proposal to modify the benchmark, but then allow applicable entities the discretion to take corrective action based solely on the results of the spatially averaged benchmark analysis while taking under advisement (‘an evaluation of possible actions’) the results of the supplemental assessment, does not satisfy the clear intent of the commission’s directive. …

“We are not persuaded by NERC’s reasoning that … existing technical limitations, specifically the limited number of observations used to define the supplemental GMD event and the availability of modeling tools to assist entities in assessing vulnerabilities, make requiring mitigation premature at this time.”

Deadline Extensions

NERC also diverted from Order 830’s directive that it consider extensions of the corrective action deadlines on a case-by-case basis.

Instead, NERC would allow entities to unilaterally revise their corrective action plan if events beyond its control — such as delays from regulatory and stakeholder processes, equipment lead times or inability to acquire rights of way — prevent implementation within the original timetable.

“Given the complexities and potential novelty of steps applicable entities may take to mitigate the risks of GMDs, we agree with NERC that there should be a mechanism for allowing extensions of corrective action plan implementation deadlines,” FERC said. “However, we would like to avoid unnecessary delay in implementing protection against GMD threats.”

The NOPR seeks comment on whether the standard should permit these “self-declared extensions” or be revised to require NERC’s case-by-case approval. “Under either option, the commission proposes to direct NERC to submit a report regarding how often and why applicable entities are exceeding corrective action plan deadlines,” FERC said.