FERC Order 881 — Are you prepared?

In an effort to more efficiently utilize our nation’s transmission grid and help lower costs for consumers, the Federal Energy Regulatory Commission (FERC) issued Order 881, which requires transmission providers to implement and use ambient-adjusted ratings (AAR) for transmission lines by July 12, 2025.

The safe usable capacity of electric transmission lines can vary greatly depending on a number of environmental factors. Historically, transmission line capacity management relied on “Static Ratings” which use conservative and fixed values for assumed weather conditions. However, Static Ratings do not account for granular variability in weather and wind speed, which affect the capacity of transmission lines and often leave significant transmission capacity on the table. Advanced transmission line ratings, including Ambient Adjusted Ratings (AAR) and Dynamic Line Ratings (DLR), factor in these environmental variables and safely calculate precise capacity limits that are often higher than static rating limits. Using AAR or DLR to manage grid capacity rather than static ratings can provide operational efficiencies that significantly increase grid capacity and reliability.

We have prepared this guide to answer some common questions about Order 881 and provide guidance on how to best prepare for the changes.

What is Order 881?

FERC Order 881 mandates new operating practices for transmission service providers, transmission owners, and system operators. The order sets several new requirements that move the power industry toward a more dynamic method of transmission line ratings that are adjusted at least hourly based on ambient temperatures and day/night solar radiation. The ruling requires the implementation of the following:

• Ambient Adjusted Ratings (AAR): Under the ruling, the implementation of AAR and seasonal ratings is required. Transmission providers– both inside and outside of organized markets — use AAR for evaluating requests for near-term transmission service (defined as transmission service that ends within 10 days of the date of the request) and use seasonal ratings for evaluating other, longer-term transmission service requests. The Final Rule requires the implementation of AAR for all lines that are impacted by air temperatures.
• Hourly Updates: RTOs and ISOs must establish and implement the systems and procedures necessary to allow transmission owners to electronically update transmission line ratings at least hourly. This helps meet the requirement for RTO’s/ISO’s to establish and maintain the systems and procedures necessary to permit the acceptance of DLRs from transmission owners that use them.
• Emergency Ratings: Transmission providers are required to use uniquely determined emergency ratings for contingency analysis in the operations horizon and in post-contingency simulations of constraints.
• Transparency: Transmission owners have to share transmission line ratings and transmission line rating methodologies with their transmission providers and for RTOs/ISOs, with their respective market monitors. Transmission providers must maintain a database of each transmission owner’s transmission line ratings and transmission line rating methodologies on the transmission provider’s Open Access Same-Time Information System (OASIS) site, or on another password-protected website.

AAR, DLR, what’s the difference?

Ambient-adjusted ratings (AARs) are often adjusted daily or hourly using ambient temperature weather modeling but still make assumptions about local wind speeds. They are calculated with the following variables:

• Ambient temperature
• Presence of Solar Radiation
• Type of Conductor
• Conductor Maximum Operating Temperature

Dynamic line ratings (DLRs) use field-based sensors to collect real-time data about the effects of air temperature, solar radiation, and wind speed and direction on the transmission line, such as conductor temperature and sag. Armed with this crucial information grid operators are able to utilize the additional capacity to optimize system operations.

The Difference: While they sound similar, DLR and AAR work differently.

• DLR is more accurate — Under DLR approaches, the use of real-time weather and wind speed data (beyond the ambient temperature data used in AAR approaches) allows DLRs to even more accurately reflect transfer capability.
• DLR can occasionally be lower (safer) than AAR — DLRs will occasionally identify that the near-term weather and/or other conditions are actually more extreme than the assumptions under other methodologies, and will therefore result in a line rating that is lower than a static, seasonal, or AAR rating would have allowed. Sometimes less is more — DLR’s additional data inputs avoid overstated ratings, reducing operational risk.
• Deploying DLR sensors brings additional benefits — DLR improves operational and situational awareness by helping transmission operators to better understand real-time transmission line conditions and potential anomalies, such as possible clearance violations. Sensor-validated DLR allows an extra layer of protection, accuracy, and deep learning compared to software-only models.

How do I plan for 881 Compliance?

Assess your current transmission system: This will help you to identify any areas where you may need to make changes in order to become compliant.

• Research different DLR and AAR methodologies: This will help you to choose the one that is best for your utility.
• Develop a plan for implementing your chosen DLR or AAR methodology: This plan should include a timeline, budget, and staffing requirements.
• Communicate with your stakeholders: This includes customers, employees, and regulators.

What are the benefits?

Utilities that are prepared early on for FERC Order 881 will be ready to go live well ahead of the compliance date.

There are a number of benefits to implementing DLR or AAR, including:

• Increased capacity: DLR can increase the capacity of transmission lines. This can help utilities to meet the growing demand for electricity without the need for costly physical upgrades.
• Improved reliability: By taking into account the ambient temperature and solar heating, DLR/AAR can help to reduce the impact of outages and blackouts.
• Reduced costs to consumers: The increased capacity reduces existing congestion and renewable energy curtailments, thereby utilizing the lower-cost clean energy generation

Additionally, utilities that adopt LineVision’s non-contact sensors also have the ability to monitor situational awareness and asset health monitoring through the same sensors, boosting potential grid reliability and resilience benefits.

How can LineVision help?

LineVision is the leading provider of dynamic line rating (DLR) and ambient-adjusted rating (AAR) solutions. We have a deep understanding of the challenges facing utilities in implementing DLR and AAR, and we have a proven track record of success with utilities worldwide.

All of our line rating solutions are FERC Order 881 compliant — We can partner with you to develop a plan for implementing DLR or AAR that meets your specific needs.

Contact us today to learn more about how we can partner with you

Legal Disclaimer: The information provided herein does not, and is not intended to, constitute legal advice; all information, content, and materials provided are for general informational purposes only. Information communicated herein may not constitute the most up to date legal or other information. LineVision waives all liability for actions you take, or fail to take, based on any content presented.

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