MINNEAPOLIS — The NERC Operating Committee got a preview of GridEx V, an update on ERCOT’s summer operations and a briefing on the June blackout in Argentina at its Sept. 10-11 meeting. Here are some of the highlights.
Argentina Blackout Briefing
NERC senior engineer Hugo Perez gave a joint Operating and Planning committees meeting a briefing on the June 16 blackout that left most of Argentina and Uruguay without power for up to 14 hours. Some 48 million people were left in the dark. Perez based the briefing on a July 3 presentation by Argentina’s minister of energy to the country’s Senate and research by the University of La Plata in Buenos Aires.
The incident on the Sistema Argentino de Interconexión (SADI) occurred shortly after 7 a.m. on a Sunday morning when Argentina’s grid had only 13,000 MW of load, well below its system peak of more than 26,000 MW.
Perez said the problem began when a 500-kV line from Colonia Elia to Belgrano suffered a single-phase fault at 7:06:24. (The cause of the fault had not been identified publicly, Perez said.)
The line is ordinarily supplemented by another 500-kV line from Colonia Elia to Campana, but that line was out of service for construction. To maintain the bus at Campana, the system was operating with a “bypass” from the Colonia Elia-Belgrano line to Campana.
At the time of the fault, Colonia Elia-Belgrano was carrying 1,650 MW from the north to the south. When the line tripped, the system should have sent a signal to generation in the north to reduce output by 1,200 MW to avoid overgeneration that could result in over-frequency.
“They do have procedures in place for outage coordination like we do, so they’re familiar with the concept,” Perez said. “But they didn’t consider that under a new topology they needed to re-evaluate their scheme. … One of the settings at [the north] end was wrong … saying decrease [generation] by zero.”
By 7:06:26, an area in the northeast, including part of Argentina and all of Uruguay, separated from the rest of the system. After teetering for a few seconds, that part of the grid collapsed.
“The blackout could have stopped there, but it didn’t,” Perez said, because the underfrequency load-shedding scheme failed on the remainder of the system.
Only “75% of their underfrequency load shedding that they have designed to operate under these conditions operated correctly; 25% of it didn’t. But things didn’t stop there.”
About two seconds after the initial fault, five generators representing “a significant portion of their generation” disconnected from the system prematurely.
Frequency dropped from 50 Hz to an initial nadir of 48.2 Hz within six seconds. Frequency rebounded for about 20 seconds, rising to about 48.5 Hz before collapsing when other generators disconnected as planned to prevent damage.
“It took them 30 seconds for them to lose not only the island in the northeast but also the rest of the interconnection,” Perez said.
He said the incident suggested a gap between “what was on paper and what was in reality.”
“They know what they need to do. The question is are they really doing it in the field?” he asked. “When you see that underfrequency is not operating as expected … it just begs the question: Are they testing their relays? If they are, how often?”
Lessons Learned: 115-kV Breaker Failure
Kelly McFarlane, an electrical engineer from Bonneville Power Administration, shared lessons learned from a Jan. 5 incident in which a tree fell into a 115-kV line during a winter storm, resulting in an outage for almost 42,000 customers of the Clark County Public Utility District in Washington state.
The tree broke a C-phase conductor, which made permanent contact with the grounded tower.
McFarlane said breakers at both ends of the line properly tripped to clear the fault, then attempted a reclose before tripping back open because of the fault. After the second trip, one of the breakers attempted eight recloses into the faulted line before faulting internally.
ABB, the manufacturer of the failed breaker, helped identify the cause of the problem: Although the instructions call for a 2- to 4-mm gap between the top of the close-coil plunger and the close lever in the breaker’s FSA-2 closing mechanism, there was no gap in this breaker.
The troubleshooting team found felt-tip markings on the breaker, suggesting the problem had resulted from prior maintenance work. The team developed a procedure for field personnel to identify and correct the problem on other breakers on the system.
“We didn’t have a step to check for this gap in our maintenance guide,” McFarlane said. “We do now.”
ERCOT Summer 2019
Dan Woodfin, ERCOT’s senior director of system operations, gave the committee a recap of the Texas grid operator’s summer, in which it had 70,000-MW peaks almost every day in August — the second hottest August on record, he said.
“We can talk about it retrospectively a little bit now, although it was still 100 degrees [Fahrenheit] on Sunday in most of Texas,” he said. “We’re hoping summer’s nearly gone.”
Woodfin said ERCOT’s tightest conditions came two hours before the daily peak, during a “trough” between the two daily wind peaks: from West Texas in the morning and coastal winds in the afternoon.
ERCOT began the summer with an 8.6% reserve margin. It set a new all-time peak of 74.7 GW on Aug. 12, and it has recorded 11 other demand marks above the record set a year ago. Last year, ERCOT broke its previous record 14 times.
Austin, home to ERCOT, exceeded 100 F during 27 of August’s 31 days.
Prices hit the $9,000/MWh cap during two energy emergency alerts, ERCOT’s first in five years, on Aug. 13 and 15.
“Where does this leave us for next year?” asked Sidney Jackson, of Rochester Public Utilities.
Woodfin said ERCOT has a large number of solar and storage resources in its interconnection queue along with some gas turbines.
“I think it’s too early to say whether we’re going to see big-time interconnection requests as a result [of 2019]. But … those prices were high enough that they should, in theory … incent additional investment.”
GridEx V
NERC’s Tom Hofstetter said GridEx V, scheduled for Nov. 13-14, will feature more government and natural gas industry involvement than in prior exercises. About 330 organizations were registered for the event as of Sept. 3, including 64 government agencies (16 of them states) and 62 gas or gas-electric entities.
GridEx IV, held in November 2017, had more than 6,500 participants, representing 450 organizations.
Votes
The committee:
- Approved the appointment of Darrel Yohnk, of ITC Holdings, to replace Gerry Beckerle, of Ameren, as chairman of the OC’s Nominating Subcommittee.
- Approved a reliability guideline, Improvements to Interconnection Requirements for BPS-Connected Inverter-Based Resources. The recommendations are applicable to transmission owners developing interconnection requirements for inverter-based resources; generator owners; transmission planners; planning coordinators; reliability coordinators; transmission operators; and balancing authorities.
- Endorsed for submittal to the ERO compliance implementation guidance, Data Exchange Infrastructure and Testing Requirements. The guidance provides examples of data exchange infrastructure reference models and tests for redundant functionality.
Save the Date
The North American Generator Forum will hold its annual meeting Oct.15-17 at NERC headquarters in Atlanta.
The North American Transmission Forum will hold a Resiliency Summit on March 31 to April 2, 2020. Details will be available in January.
— Rich Heidorn Jr.
