by Kelso King, Grid Monitor
Source – Grid Monitor
At the August 11, 2020 ERCOT Board meeting, Woody Rickerson, ERCOT’s Vice President of Grid Planning & Operations, reported on transmission-related issues, highlighting how the grid is changing and things that can be expected in the future. He suggested that no action items are currently involved but this is a preview of coming discussions.
Regional transmission constraints are likely to increase over the next five years and congestion is occurring in many areas. The most notable constraints include Northwest Dallas-Fort Worth import, West Texas export, Delaware Basin load serving, South Texas import and export, and Houston/Freeport import.
Mr. Rickerson suggested that a lot of emerging constraints involve complex grid stability issues, which will present an ever increasing challenge for ERCOT and stakeholders going forward, requiring more training, more detailed models, and more computing power.
Although there will be congestion issues, Mr. Rickerson reported that planning studies are not showing transmission constraints having an impact on resource adequacy at this time.
ERCOT anticipates emerging reliability and/or economic issues in six different geographical areas. Mr. Rickerson explained that reliability issues are driven by load growth, while economic issues are typically driven by generation growth.
Mr. Rickerson noted that five of the six areas involve stability constraints. Issues in four of the six areas are driven by load growth, issues in four are driven by generation growth, and issues in two are driven by both load and generation, as indicated below:
· Delaware Basin: Reliability
· West Texas Export: Economic
· South Texas Export: Economic
· Northwest Dallas-Fort Worth: Reliability and Economic
· Houston/Freeport Import: Reliability and Economic
· South Texas Import: Reliability, both import and export
Maps of load and generation changes in Texas reveal an underlying trend, that generation is moving further and further from load over time. Load growth is occurring across the state but most heavily in the areas you would expect, urban areas and West Texas, and is often on the edge of the system, making it inherently harder to serve.
The middle map shows that the oldest generation tends to be nearest the highest load growth areas and is, therefore, most likely to retire in coming years. Mr. Rickerson explained that generation retirements have a similar effect to load growth, adding that p Part of the challenge is for areas that are experiencing load growth while anticipating generation retirements.
Most expected new generation is occurring in the western half of the state and, aside from West Texas, is not where load is expected to increase. Mr. Rickerson suggested that, when considering congestion issues, it is important to keep in mind that an increasing amount of power is flowing from the North and West to the East and South.
Northwest Dallas-Fort Worth Import
According to ERCOT studies, the combination of generation development northwest of the Dallas-Fort Worth area and load growth within the area is expected to exceed transmission capacity in this region. This is one of the most congested areas in recent planning studies and ERCOT is actively analyzing options to relieve these constraints. Mr. Rickerson noted that Competitive Renewable Energy Zone (CREZ) transmission provided a lot of power into the DFW area and future congestion solutions in this area are the next logical improvements to the CREZ system. He added that this is the only area that also has thermal constraints.
West Texas Export
CREZ was designed to accommodate 18.5 GW of wind generation but 28 GW of renewable generation is expected to be connected in West Texas in the near future. As a result, stability limitations are expected to lead to high levels of congestion on West Texas exports so ERCOT is analyzing transmission upgrades in the region. Mr. Rickerson noted that West Texas load growth will offset some of that congestion, as will Lubbock Power & Light’s upcoming integration into ERCOT. ERCOT is analyzing transmission upgrades to relieve this congestion as part of its 2020 Regional Transmission Plan.
The Delaware Basin is a sub-basin of the Permian Basin in Far West Texas. This area has been experiencing annual peak load growth of over 10% since 2010, compared to ERCOT’s 1.5% annual growth rate during the same period. The peak load in the Delaware Basin in 2010 was approximately 1,900 MW, compared to a peak of 4,588 MW in July 2020. This is also a stability concern, which makes it more complicated. In 2019 ERCOT completed an assessment of the Delaware Basin and identified a 5-stage roadmap of transmission upgrades to serve continued oil and gas load growth in the area.
South Texas Import and Export Constraints
Mr. Rickerson noted that the South Texas import constraint is a reliability issue, while the export constraint is an economic issue. Five of the existing twelve Generic Transmission Constraints, which are used to manage stability limits in operations, are located in South Texas. A proposed Liquefied Natural Gas facility in the Rio Grande Valley could require up to $1.2 billion in transmission improvements. Additional wind and solar generation development in the area may also lead to further stability constraints.
The Houston Import Project went into service in 2018. The Freeport Import Project was approved in 2017 and will be completed in 2021. Mr. Rickerson noted that the 2014 Houston Import Project study indicated additional upgrades would be needed by 2027 to continue to meet reliability criteria and, in fact, that is now being seen. Recent planning studies indicate increasing amounts of congestion on the transmission lines importing power into the Houston and Freeport area in coming years.
New Generation Challenges
Mr. Rickerson discussed transmission challenges caused by new generation. He noted that the majority of new generation projects are inverter-based resources (IBRs), i.e., primarily wind and solar. Because of their short development timelines, IBRs are added to ERCOT’s planning models only six months to two years ahead of their commercial operation date. Transmission upgrades to resolve congestion, on the other hand, can take up to six years to complete. As more IBRs are connected, there is going to be a lag, resulting in congestion.
Remedial Action Scheme (RAS) for New Generation
A Remedial Action Scheme (RAS) is a hard-wired protection scheme that detects predetermined system conditions and automatically takes corrective action. Corrective actions may include, but are not limited to:
· Transmission reconfiguration and load shedding for reliability, including opening a switch or disconnecting a line
· Generation tripping, which is used to allow generation resources to generate beyond local transmission constraints.
Mr. Rickerson reported that an increasing number of RASs have been requested for interconnecting new generation resources. RASs have reliability impacts and incorporating them into the system is something ERCOT takes very seriously because they require a lot of study due to their multiple interactions.
An August 21, 2020, ERCOT will host a workshop including a discussion of reliability concerns associated with incorporating a large number of RASs into the grid. Mr. Rickerson noted that ERCOT’s comments concerning NOGRR215 provide a detailed explanation of ERCOT’s concerns regarding RASs. Mr. Rickerson informed the Board that they are likely to hear more about RASs in the future due to the fact that IBRs can be constructed so much faster than transmission.
Mark Carpenter, representing Investor-Owned Utilities, suggested that, while Transmission and Distribution Service Provider (TDSPs) do not like RASs just to serve load, they are “a necessary evil.” He asked whether ERCOT had given any consideration to using different load forecasting methodologies for the perimeters of ERCOT.
Mr. Rickerson replied that they had not looked at forecasting perimeter load separately but that this distinction would be something to think about because perimeter loads create some special challenges at times.
Mr. Carpenter suggested that, while ERCOT does a great job of predicting ERCOT’s total load, there are some offsetting regional errors that cause local issues. He noted that whether there is an adequacy issue from lack of generation or local congestion, either way, customer load has to be shed.