Sub-zero temperatures from Toledo to Tennessee pushed PJM to its limits last week as the RTO overcame the loss of nearly 40,000 MW of generation during an arctic blast that set a new winter demand record.

Demand response, voluntary conservation and imports helped PJM avoid shedding load as demand hit 141,500 MW Tuesday evening, besting the previous winter peak — set Feb. 5, 2007 — by nearly 5,000 MW.

The RTO survived Tuesday’s peak despite about 38,000 MW in generation outages, almost 20% of its installed capacity. “We really exhausted every megawatt we had on the system,” Adam Keech, director of wholesale market operations, told the Market Implementation Committee in a briefing Wednesday.

Some plants failed to start, suffered tube leaks or were unable to convert to backup fuel. “We’ve seen everything,” Executive Vice President for Operations Mike Kormos said during a press conference Tuesday morning.

What sent temperatures plunging and power and natural gas prices skyward was an unusual visit by the polar vortex, a low pressure system that normally circles around the North Pole.

Temperatures of -10 or below were recorded Tuesday in Ohio, Michigan and Pennsylvania. The negative numbers reached as far south as Kingsport, TN, which reported -1 and Blacksburg, VA, which registered -5.

PJM power prices were above $200/MWh for most of the period from Monday evening through Tuesday evening, peaking at more than $1,800/MWh during Tuesday’s morning and evening peaks.

Natural gas for Tuesday delivery hit a record $95/mmBtu at Transco’s Zone 6 non-New York hub in PJM, Natural Gas Intelligence reported. U.S. gas demand hit a record 130 billion cubic feet per day Monday, topped by a new record of 134 Bcf/d Tuesday, according to Bentek Energy.

Generators told PJM, “`I can get gas but it’s very expensive. Do you still want it?’” Executive Director of System Operations Mike Bryson told Platts Energy Week later. “And we were in a position where we needed every megawatt we could get on the system.”

One bright spot: The gusts that accompanied the cold boosted PJM wind production to more than 3,000 MW, according to the American Wind Energy Association.

Below is a chronology of PJM’s response to the arctic blast, based on PJM records and briefings from PJM officials and industry news reports.

Monday, Jan. 6

PJM braced for the arrival of the vortex Monday as subzero temperatures began moving east from the western portion of the RTO. Shortly before noon, PJM issued a Maximum Emergency Generation Alert for Tuesday for the entire PJM RTO — a signal that the RTO may need every available megawatt of generating capacity. They also issued a press release calling on consumers to conserve power the following day.

PJM and state regulators urged consumers to reduce energy use during the emergency. “Every little bit helps,” Kormos said. “There’s 60 million people in our footprint. If everyone does their part, that could easily add up to one nuclear plant, which is 1,000 MWs.”

“We’re very close [to generation limits],” Kormos added. “The last couple hundred megawatts could allow us to not have to take any forced interruptions.”

PJM received a waiver from the Federal Energy Regulatory Commission under Order 787, allowing RTO officials to share information with natural gas pipelines serving the region. PJM held conference calls with pipelines Friday and Monday and individually validated gas nominations for the RTO’s gas generators. Keech said there were no natural gas curtailments.

“The pipelines came through pretty well,” Gary Helm, lead market strategist, told the Market Implementation Committee in a briefing. “We only saw two compressor outages.”

At about 5 p.m., the RTO lost about 1,500 MW of generation, including the FirstEnergy’s 911 MW Beaver Valley nuclear unit 1, which tripped after a transformer malfunction.  Operators requested synchronized reserves and shared reserves from NYISO. Load mounted faster and higher than expected, topping off 5,000 MW above forecast at 131,900 MW.

Keech said operators’ ability to forecast load was hamstrung by a lack of comparable temperature data. “We couldn’t find a temperature set [with extreme cold throughout the RTO] for the last decade. And if you go back that far the [RTO] footprint was so different it’s probably not even useful.” Keech said.

The synch reserve event was ended after a little more than an hour at 6:09 p.m. Shortly before 7:30 p.m., another large generator tripped.

At 7:50, with reserves growing short, operators reduced voltage across the RTO by 5% to help them through the evening peak. The action, which lasted about an hour, triggered scarcity pricing ­— sending prices briefly above $1,000/MWh.

Tuesday, Jan. 7

Overnight, operators became alarmed after the “valley load” — the lowest load of the day —came in 4,000 MW higher than the projected 116,000 MW. About 2 a.m., expecting a morning peak of 140,000 MW, operators issued a request for emergency energy for 6 through 11 a.m.

Shortly before 3 a.m., they issued a warning that they might again reduce voltage.

At 4:30, they issued a call for 1,900 MW of emergency demand response and issued a Maximum Emergency Generation Action, notifying market participants that off system energy sales from PJM capacity resources may be recalled. Demand response provider EnerNOC Inc. said it was the largest winter dispatch in PJM history.

About 1,100 MW of emergency energy began flowing from MISO and NYISO at 6 a.m., but at 6:30 operators called on 100% synchronized reserves to respond to a low Area Control Error. A second spin event was initiated shortly after 8 a.m., when an unnamed unit tripped.

The morning peaked at 138,600, a new — if short-lived — winter record. Prices were in the $1,800/MWh range from 7 to 11 a.m.

At 3 p.m., operators again called on DR for an evening peak projected at 142,000 MW. However, an unexpected influx of imports — as much as 10,000 MW — allowed them to cancel the DR call shortly after 6 p.m.

The evening peaked at 141,500 — below projections but a new winter record nonetheless.

Bryson credited voluntary conservation. “There were times when we thought we were going to be short on reserves and the load just didn’t come in,” he said. “And it’s probably representative of a very good consumer response.”

Wednesday, Jan. 8

Expecting a morning peak of 136,600 MW, PJM again issued a Maximum Emergency Generation Action, called on DR and issued a request for emergency energy.

Generator outages would peak Wednesday morning at 39,520 MW. But with temperatures rebounding, the morning peak would hit only 134,500. With load coming in lower than expected, the RTO cancelled the DR call at 6:30 and the Maximum Generation Action at 9 a.m.

The crisis was over.