Research & Technical Content

Ratings Information Session, FERC 881 Update and WindSim DLR Field Trial
As part of a periodic update EPRI provided a presentation on FERC 881 research and potential pitfalls of adopting AAR. This was followed by a presentation by WindSim on their DLR technology that was deployed in the field at NYPA. Members have received previous updates on this technology in EPRI reports and in an ITC Task Force presentation by NYPA. The presentation provides the performance analysis as provided by WindSim with several valuable insights that can help guide future DLR adoption.

Capacity Gains from Thermal Uprating
There are several methods that can be deployed to increase power flow on new and existing lines. One method is to thermally uprate the operating temperature of assets. This could be uprating a traditional material like ACSR to run above the traditional limits, or to deploy hardware capable of high temperature operation. This summary provides an overview of how much capacity can be gained from thermal uprating. The capacity gains are not linear so there are cases where it provides significant benefit, and cases where the gains are minor.

Ambient Adjusted Ratings and Ferc 881
North American utilities are being required to adopt ambient adjusted ratings (AAR). There are technical challenges to defining and applying AAR. In many cases AAR can significantly increase risks of violating clearances and thermally damaging assets. Several case studies have been performed to document how AAR influence capacity and system risks.

Commonly Used Terms and Abbreviations
Ratings engineers and line designers often use shorthand and acronyms. This can be particularly confusing for new staff who are less familiar with these new terms. Especially when many are so similar looking. ACAR looks like ACSR in a catalog, but the two materials have very different properties and design requirements. This page is intended to be a living document that evolves to include more terms over time, as such the list is not currently exhaustive but does contain many commonly used terms.

Conductor Emissivity Testing
When calculating transmission ratings, performing inspections, and conducting LiDAR surveys the properties of the overhead conductors are a key factor. Often assumptions are made about conductor emissivity and absorptivity which can result in errors, risks, and costs. EPRI is performing research to identify the correct values to use for emissivity and absorptivity for new, aged, and coated conductors.

Solar Heating
Objects heat up in the sun in a prosses called absorption. When sunlight strikes an object, it causes the atoms and molecules it strikes in an object to vibrate, this vibration energy is what we commonly know as heat. Some materials are more effective at absorbing sunlight than others.

Variation in AAR based on daily Air Temperatures
As demand for electricity increases we push the grid closer and closer to its peak capabilities. Physical upgrades can be done such as voltage upgrades or conductor replacements, but these processes are costly and time consuming. To get the most out of new, upgraded, and existing lines requires adopting more complex methods of establishing and maintaining line ratings. One approach seeing increased adoption in the US is Ambient Adjusted Ratings (AAR).

Sunrise-sunset Calculator for Day-night Ratings
Many utilities are transitioning to more complex ratings methods. For example, utilities subject to FERC 881 are adapting to requirements for day and night ratings. This calculator provides a technical basis for determining if day or night ratings should be applied based on the specific location and time of year.