Pilgrim nuke goes offline as Northeast buffeted by winter storm

Dive Brief:

The Pilgrim nuclear plant in Massachusetts was removed from service on Thursday afternoon as a winter storm buffeted the region, forcing grid operator ISO-NE to turn to power imports and other resources to supply electricity.
The outage was due to the loss of one of two power lines feeding into Pilgrim, plant owner Entergy said, and the plant will remain offline to perform maintenance. ISO-NE officials said local reliability was never in danger, but the outage will "further challenge the region on fuel availability" as gas and oil plants generate at higher levels.
Officials at the New York ISO reached out to transmission owners in advance of the severe winter storm, preparing for up to a foot of snow and winds up to 40 mph as a two-week cold snap finally comes to an end.

Dive Insight:

In both New England and New York, frigid air has increased demand for natural gas, pushing gas prices higher and resulting in increased wholesale electricity prices. Dual-fuel generating units have been key to maintaining reliability, with many switching over to cheaper oil to generate energy.

Friday and Saturday are likely to be the final — and harshest — days of a winter cold snap that has sent temperatures plunging all along the eastern seaboard. In New England, the grid will have to do without the 685 MW Pilgrim nuclear plant, which went offline shortly after 2 p.m. on Thursday.

The cause of the outage is still under investigation, Entergy said in a statement, but it involved one of two power lines that allow the plant to feed electricity to the grid. The plant will remain offline to conduct maintenance activities that cannot be performed when it is generating. The exact timing of its full reboot is considered "business sensitive," and was not disclosed.

In the immediate aftermath, ISO-NE turned to imports from New York to compensate for the loss of power. The ISO's power import chart for its Roseton intertie with New York shows a spike in imports shortly after 14:00 (2 p.m.) on Thursday, spokesperson Marcia Blomberg pointed out:

Power imports are denoted in negative numbers, so the surge in power imports appears as a dip in the Roeston flow shortly after 14:00 (2 p.m.). The higher imports came close to the 1,600 MW limit for the Roeston intertie (orange line).

ISO-NE

In the hours following the outage, oil, gas and particularly hydroelectric generation combined to make up for Pilgrim's lost power and meet peak power demand in the evening, which for ISO-NE was just above 19,500 MW after 5:30 p.m.:

Hydroelectric generation (bottom blue line) ramped up to compensate for the Pilgrim outage (dip in yellow line after 14:00) and to meet the evening peak.

ISO-NE

While there were no local reliability problems, the outage of a large, non-gas generator was precisely the scenario ISO-NE was trying to prevent, Blomberg told Utility Dive earlier in the week. With Pilgrim offline and gas being diverted for home heating, oil-fired plants may burn through their onsite fuel stockpiles more quickly.

ISO-NE has a Winter Reliability Program that incentivizes dual-fuel generators to keep 10 days of fuel onsite (or 85% of their storage capacity, for smaller generators). At peak, oil-fired generation has hovered between 5,000 and 6,000 MW this week. Without replenishment, an ISO-NE planning document shows generators could keep that level of output going for less than a week, though the oil-fired plants ramp down to a lower output at night.

Operating between 4,000 and 6,000 MW of output around the clock, ISO-NE oil generators would have less than a week of fuel onsite. Actual output has been lower, however, and fuel replenishments continue.

ISO-NE

In New York, the storm response has been more routine. Grid operators NYISO says its system has been tested, but flexibility has been key to maintaining reliable operations.

Generator performance has been good, with very few outages and no lack of fuel or emission limitations, the ISO said yesterday in a conference call. All six of New York’s nuclear units are online. Major interstate and intrastate gas pipelines and gas distribution systems are also functioning properly, and ISO officials said there have been no forced high voltage transmission outages.

However, transmission lines and gas pipelines are all running at max capacity right now.

"Almost 50% of the generation fleet is able to rely on oil as a backup," New York ISO Executive Vice President Rich Dewey said on the call yesterday. "Fuel diversity allows us to be very well positioned for an event like this."

Peak demand anticipated on Friday would fall just shy of the ISO´s high-end projection for the season.

In November, the NYISO issued a winter preparedness report anticipating a peak demand of 24,365 MW; last winter peak demand reached 24,164 MW, though weather was milder. The state´s record winter peak was set in 2014 during polar vortex conditions that pushed demand to 25,738 MW.

NYISO officials expect demand on Friday of 24,340 MW, though it could edge higher if temperatures decline lower than anticipated. In ISO-NE, demand is expected to hit 20,450 MW, slightly higher than the forecast and actual demand on Thursday.