PJM clarifies events surrounding recent Ohio load shedding, power price spikes

PJM Interconnection June 29 clarified the events that led to multiple recent load shed declarations in Ohio and the operations it took to maintain power system control amid hot weather and power line failures that resulted in power price spikes.

"First we'll talk about the capacity situation and then talk about some of the storms in the latter part of the week and the operating issues we had around the Columbus area," Paul McGlynn, PJM's executive director of system operations said during an in-person and remotely held Markets and Reliability Committee meeting.

Monday June 13 started out like a typical summer day with PJM expecting a power demand level of around 128,000 MW and there was a hot weather alert in effect for the EKPC zone, McGlynn said, adding that reserves were covered and from a generation perspective the grid operator had plenty of resources.

However, things started to change as the operating day progressed with the morning load coming in about 1,800 MW higher than forecast, he said. The total load forecast for the day was nearly 128 GW with an actual peak of 136 GW, according to a PJM presentation given during the discussion.

By around lunchtime, load was around 8,000 MW higher than PJM had forecast and by early afternoon the grid operator had a couple of power generation resources come offline totaling 1,150 MW. That was followed by a constraint and overload on the Peach Bottom-Conastone 500 kV transmission line, according to the presentation.

"Operationally that limits some of the resources that because of the constraint we are able to dispatch," McGlynn said.

PJM got through the operating day and used "a bunch of combustion turbines" that do not run all that often and there were some fairly high power prices, he said. Real-time power prices jumped over $3,000/MWh into the evening of June 13 and the on-peak real-time daily average power price at the AEP-Dayton hub was $535.88/MWh, according to PJM data. The on-peak real-time average price at the hub in May was $85.08/MWh by comparison.

Load forecast, storm impacts

There was widespread under-forecasting of temperatures throughout the entire PJM footprint on June 13, along with the first occurrence of extremely high heat indices this year and a "drastic increase" in temperature and load from the previous day, according to PJM's presentation.

Additionally, storms that would have lowered load did not materialize until after the load had peaked. And unfortunately, when the storms did develop and they were severe with several tornadoes touching down in the Columbus area, McGlynn said.

PJM issued load shed directives in the AEP service territory in Ohio June 14-15 related to the thunderstorm damage that knocked out multiple 138-kV transmission lines and overloaded other lines, causing congestion and localized power price spikes.

Several dozen bulk electric lines were down on June 14 and toward early afternoon several 138 kV facilities tripped offline with a number of transmission facilities rated above their "load dump" rating so PJM alerted local utility AEP to shed load to deal with the transmission overloads, PJM said.

There were additional thermal issues impacting the bulk power system which could have led to a cascading event, leading PJM to issue a second load shed directive to AEP at around 7:30 pm, McGlynn said.

By 10:30 pm June 15 PJM was able to cancel the load shed events. PJM staff said the grid operator and AEP are conducting more detailed analysis into the situation and multiple reports will be released.