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FERC Opens Inquiry on Use of Dynamic Line Ratings to Promote Grid Efficiency

Paul Dumais's picture
CEO Dumais Consulting

Owner and CEO of Dumais Consulting ( which provides expert ratemaking services to energy companies. Dr. Dumais is a ratemaking and regulatory expert who specializes on...

  • Member since 2018
  • 149 items added with 114,793 views
  • Mar 8, 2022

FERC today launched an inquiry to examine whether the use of dynamic line ratings (DLRs), which are based on a wide range of weather and line-specific factors affecting the operation of electric transmission lines, would help ensure just and reasonable wholesale rates by improving the accuracy and transparency of line ratings.   Today’s Notice of Inquiry (NOI) in Docket No. AD22-5 builds on Order No. 881, which FERC approved in December of last year. Order No. 881 directs transmission providers, for certain transmission evaluations purposes, to use ambient-adjusted ratings (AARs) as the basis for evaluating near-term transmission service as well as for the determination of the necessity of certain curtailment, interruption or redispatch of near-term transmission service. Transmission line ratings represent the maximum transfer capability of each transmission line. These ratings can change based on weather conditions.   Order No. 881 found that line ratings based on conservative assumptions about worst-case, long-term air temperature and other weather conditions can lead to underutilization of our transmission grid. Therefore, requiring all transmission providers to use AARs will better utilize the grid and help lower costs for consumers.   Order No. 881 also acknowledged that transmission line ratings could be based on factors beyond forecasted ambient air temperatures and the presence of solar heating. Applying these factors to reflect other weather conditions like wind, cloud cover, solar heating intensity and precipitation, as well as transmission line conditions such as tension or sag, could lead to greater accuracy and enable greater power flows. In addition, the Commission explained that the use of dynamic line ratings can detect situations where flows should be reduced for safe and reliable operation and to avoid unnecessary wear on transmission equipment.

FERC believes additional information is required to evaluate the relative benefits, costs and challenges of dynamic line rating implementation. Today’s NOI seeks to further explore: whether the lack of DLR requirements renders current wholesale rates unjust and unreasonable; potential criteria for DLR requirements; the benefits, costs and challenges of implementing DLRs; the nature of potential DLR requirements; and timeframes for implementing potential DLR requirements.

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John Simonelli's picture
John Simonelli on Mar 10, 2022

The concept of dynamic line ratings has been around for a long time. The catch 22 in all of this is DLR only addresses thermal transfer capabilities, it does not address potential stability and voltage limits. Raising transfers across the system can potentially exacerbate both the stability and the voltage response of the system. Detailed studies would have to be conducted to confirm additional problems are not introduced by upping the transfer capability. Also, in many instances there are other limiting elements besides just the conductors, one must factor in all the substation gear, breakers, disconnect switches, wave traps, etc. All of that also needs to be coordinated with system protection to ensure one doesn’t introduce spurious tripping with increased transfers. So, while upfront DLR can help alleviate some of the bottlenecks it is not the all-encompassing solution.

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