WATT to FERC: GETs have unique value in extreme weather

August 26, 2022, Washington, DC – Today the WATT Coalition filed comments to the Federal Energy Regulatory Commission in their Notice of Proposed Rulemaking on Transmission System Planning Performance Requirements for Extreme Weather.

WATT calls on FERC to require planners to evaluate dynamic line ratings, advanced power flow control and topology optimization in their Corrective Action Plans for both steady state and stability planning events. Grid flexibility is crucial to reliability during extreme weather. 

GETs allow grid operators to monitor and respond to conditions on the grid, supporting reliability in extreme weather. Individual technologies each contribute to safer and more flexible grid operations and can mitigate reliability risks during severe weather. Read the full comments here, and see below for explanations of each technology’s resilience and reliability value in severe weather conditions.

Dynamic Line Ratings:

DLR monitors real-time ambient conditions, such as wind speed and temperature, which cool or heat transmission lines. These factors are used to calculate the true capacity of transmission lines, based on their thermal limits. In cold or windy conditions, DLR allows significantly more power flow than a static rating, which is based conservatively on hot and still conditions. FERC’s order to use Ambient Adjusted Ratings will support greater line capacity in standard conditions, but DLR is especially helpful in extreme scenarios when multiple weather conditions should be factored into line rating. Basing line ratings on real-time data also detects when flows should be reduced to continue safe and reliable operation in extreme heat. In addition, DLR technologies are also helpful in identifying damaged or aging infrastructure, thereby allowing operators to respond more quickly to outages, including those caused by extreme weather. 

GETs such as DLR can be a critical tool to improve grid reliability since DLR sensors can also evaluate conductor health and detect adverse phenomenon like galloping, conductor creep, excessive sag, blowout, conductor fatigue, ice accretion and wildfires. When DLR systems are integrated into utility operations, real-time awareness can be routed directly into the utility’s EMS system for real-time system awareness. 

Advanced Power Flow Control

Power flow control technologies are uniquely able to actively balance electrical flows on transmission lines. The hardware can intelligently raise or lower the impedance, or the opposition to current, in real time to ensure that power is delivered on lines that have available capacity. APFC technology expands on this function with enhancements such as faster and more flexible deployment options, easy scaling to meet the size of the need, and ability to relocate when needed elsewhere on the grid. 

During extreme weather events, outages, shifts in resource mix availability, and even increased customer demand, APFC can alter the flow of power on the grid, ensuring that lines are not overloaded and rerouting power along underutilized transmission corridors to ensure delivery.  

Destructive natural disaster events—such as Superstorm Sandy underscore the importance of planning in ways that build optionality into grid operations. APFC allows operators to rapidly respond to changes in available generation and transmission to reduce the length and scale of outages and facilitate optimal system recovery. 

Topology Optimization

Transmission topology optimization software models the grid’s network and power flow conditions to identify ways to reroute power flow around congested, overloaded, or compromised transmission elements. These “reconfigurations” are implemented through switching on or off existing high voltage circuit breakers.  

In normal operations, topology control increases the transfer capacity of the grid by distributing flow more evenly over the network. When extreme weather causes outages or other changes to power flow, topology optimization can identify a suite of operational changes to stabilize the grid and deliver as much power as possible. The feasibility and benefits of optimally reconfiguring the transmission grid under extreme event conditions has been showcased in studies of Corrective Action Plans in SPP (see presentation by Ruiz et al in FERC Docket AD10-12-009, slides 23 and 24), where in all three existing Corrective Action Plans studied, the use of load shedding was avoided by using one or two optimal grid reconfigurations.