'Extremely rare' issue with LA area power lines caused Memorial Day weekend outage, officials say

A longstanding lack of long-range transmission lines in south Louisiana, which limits the amount of power that can be moved in from other areas, contributed to an “extremely rare” problem with the region’s electric grid and led to the forced power outages over the Memorial Day weekend in the New Orleans area, officials said Tuesday.

During a New Orleans City Council meeting that shed new light on the hours-long outages, executives with Entergy and the region’s electric grid operator, known as the Mid-Continent Independent System Operator, or MISO, said that the lack of transmission lines, combined with warmer-than-normal temperatures and a series of unplanned outages at power plants run by Entergy, created difficult conditions for the grid before the outage.

MISO officials, who serve as the “air traffic controllers” of the electric grid, were working to manage the problems heading into the holiday weekend by reconfiguring where power flowed.

But on Sunday at 4 p.m., MISO suddenly realized that their reconfiguration was no longer working. If a transmission line between Mississippi and Louisiana also went offline, it would cause “catastrophic” outages that could have spread rapidly throughout the region.

Acting under rules aimed at keeping the whole system from crashing, MISO officials told Entergy and Cleco they had 30 minutes to shed 600 megawatts of power, which led to blackouts for 100,000 customers in the region. Out-of-state transmission controllers for Entergy picked specific neighborhoods to turn off, said Charles Long, Entergy’s senior vice president for power delivery.

“There was enough energy online,” said Long. “We couldn’t move all the energy we needed in south Louisiana from outside the area.”

Louisiana electric grid problems long known

The presentations by MISO and Entergy illuminated long-existing problems with south Louisiana’s electric system: A lack of long-range transmission lines — the “interstate highways” of the grid that let electricity flow across states and regions.

MISO operates the grid across a large section of middle America, from Canada to the Gulf of Mexico. Entergy joined the system in 2013 amid pressure from the U.S. Department of Justice, which alleged Entergy was engaging in anti-competitive behavior by wielding its transmission system and fleet of gas plants to crowd out competitors. Entergy said it was following federal law. 

The DOJ also sought to have Entergy sell its transmission business, but a deal to do so fell through. And since then, advocates for more transmission argue Entergy has slow-walked a needed build-out of long-range lines. Entergy has countered that its plans, largely focused on building new gas-fired power, are more cost-effective for customers. 

That state of affairs is what grid operators were forced to navigate last month. Todd Hillman, the chief customer officer for MISO, said there was ample power in Mississippi, for instance, but not enough transmission lines to send it to the New Orleans region.

Regulators have long known about the bottlenecks, and on Tuesday, consumer advocates and some City Council members called on Entergy and MISO to move more quickly to build out more long-range transmission lines.

“So many of these problems have roots in issues we’ve known about for decades,” said Logan Burke, head of the Alliance for Affordable Energy. “The bad news is the chickens have come home to roost.”

Councilmember Helena Moreno asked MISO to accelerate an ongoing effort to build more transmission to alleviate bottlenecks throughout the operator’s southern region, which is dominated by Entergy. Utilities in MISO’s northern region have outpaced those in MISO’s southern region in building long-range transmission infrastructure. 

No warning

During the council meeting, officials with MISO and Entergy also sought to explain why there was no warning for the public or regulators about the outage when they knew the grid was under stress. Council Utilities Committee Chair JP Morrell said he didn’t learn about the blackout until after his own lights went off.

“This can never happen again where we’re all in the dark and no one knows why until 30 or 45 minutes later,” Morrell said.

Hillman said that the blackout was unlike traditional load shed events, which typically happen on very hot or cold days when the demand for electricity outstrips the supply.

Instead, the problem was that transmission lines were constrained to the point that it was threatening the grid’s stability. When that happens, MISO is required to fix the problem within 30 minutes, he said.

“These events are extremely rare,” Hillman said.

JT Smith, MISO’s executive director of market operations, said he can only recall two other instances of this type of forced blackout in his 20 years at MISO, once in Illinois during Winter Storm Uri in 2021 and another in Baton Rouge over a decade ago.

MISO and Entergy promised to work to figure out a way to better communicate to regulators and the public if it runs into the same problem with the transmission system again.

Entergy and MISO officials said they were aware the grid was facing strain on Friday and Saturday, and while they didn’t expect to have to initiate forced blackouts, they indicated they would look at communicating those issues to the public.

Seven generators had unplanned outages in the days leading up to the blackouts, including River Bend, a nuclear facility north of Baton Rouge that was taken offline because of a leak. It’s not yet clear which other power plants went down or why.

A large transmission line in western Louisiana was also out of service because of a tornado in March, and wasn’t repaired until several days after the blackout.

Entergy New Orleans CEO Deanna Rodriguez apologized for the outage and said “this has never happened to us before.”

She was unable to say whether customers might pay more on their electric bills because of the event.