PG&E Model Didn’t ID Line That May Have Started Zogg Fire For Potential Shutoff

Fire flames

PG&E said in a response to Judge William Alsup on Monday that their model didn’t identify the power line which may have sparked the Zogg Fire for potential shutoff.

The response, which was filed in federal court in San Francisco, provided responses to multiple questions asked by Alsup.

Those questions included:

PG&E shall please explain its role in the ignition of the Zogg Fire

“PG&E has not determined what role, if any, its equipment may have had in the ignition of the Zogg Fire,” PG&E wrote in the response. PG&E also stated that Cal Fire has not determined the cause of the fire, nor provided PG&E with access to the evidence they collected.

PG&E noted that smoke “that may be associated with the Zogg Fire” was visible in footage at 2:42 PM on September 27. PG&E said that its equipment in the area detected multiple anomalies in the area the fire began at 2:40 PM, 2:41 PM, 2:42 PM and 2:43 PM, as well as multiple anomalies after that.

PG&E noted that these anomalies did not last long enough for its equipment to trigger automatic shutdowns.

“[This] avoids the operation of the protective devices in response to transient conditions, such as normal changes in loads on the line,” PG&E said, explaining that disruptions need to last 20-25 seconds before they trigger shutoffs to avoid unnecessary shutoffs.

PG&E shall also describe the PG&E equipment removed by Cal Fire and the location of the equipment when it was in use

PG&E noted that Cal Fire collected three SmartMeters which recorded electricity use at three properties in the area of the fire, conductor, two shattered insulators, one piece of crossarm hardware and a burned crossarm.

PG&E shall additionally describe the extent of trimmed and untrimmed vegetation in the area near where Cal Fire took possession of PG&E’s equipment

PG&E stated in the response that the area the fire started in was photographed in July 2019 then subjected to a routine vegetation management patrol from March to April 2020. Tree maintenance was then completed in April 2020, according to the response.

“Based on a review of its records, PG&E has not identified at this time any trees in the area of interest for which tree work had been prescribed but was incomplete at the time of the Zogg Fire.”

However, a lawyer overseeing PG&E’s probation told Alsup last week that his team found dangerous trees in locations not related to the Zogg Fire which PG&E hadn’t dealt with, such as a tree close enough to electrical equipment for its leaves to be singed.

PG&E shall also explain whether the equipment taken by Cal Fire was transmission line equipment, distribution line equipment, or substation equipment

PG&E responded that the equipment taken by Cal Fire was distribution line equipment.

PG&E shall supply to the Court all documents, emails, text messages, reports, voicemails and any other materials, in paper or electronic form, leading up to and concerning the decision to leave energized the line or circuit in question that possibly led to the Zogg Fire.

“The models that PG&E employs to determine the [shutoff] scope did not identify the Girvan Circuit for potential de-energization on September 27, 2020,” the response states, adding, “accordingly, there was no ‘decision to leave energized the line’.”

PG&E explained that potential public safety power shutoff (PSPS) events are identified by a risk model developed by “PG&E’s expert meteorologists.” This model combines two inputs, an OPW model and a Utility FPI model.

The OPW model “is based on an analysis of wind speeds for every unplanned outage that occurred over the last decade and forecasts the probability of unplanned outages associated with wind events occurring in PG&E’s service area,” according to the response.

The Utility FPI model predicts the probability of a fire of 1,000 acres or more in specific location based on 30 years of meteorological data, including weather, climatology and fuel moisture data, and 26 years of historical wildfire data, according to PG&E. This model considers factors such as temperature, wind, humidity, 10-hour dead fuel moisture, live fuel moisture, and landcover type, meaning grass, shrub/brush or forest.

“While no single factor determines the scope of a PSPS event, generally the wind speed threshold for de-energization is sustained winds above 25 mph and wind gusts in excess of approximately 45 mph,” the response states. The response notes that, at the start of the Zogg Fire, the two closest PG&E weather stations to the location of the fire recorded sustained winds under 15 mph and wind gusts of between 23 and 28 mph.


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