Oncor, a U.S. transmission and distribution utility, successfully completed a Department of Energy (DOE) Smart Grid Demonstration Program (SGDP) showing that the real-time information provided by Nexans’ Dynamic Line Rating (DLR) technology can contribute to increasing the power carrying capacity of existing overhead line assets and reducing congestion.
For the core component of the SGDP, Oncor installed the DLR technology on eight 138 kV to 345 kV transmission circuits located in Central Texas, resulting in a power increase of up to 14%. Oncor is continuously looking for new technology that will bring added value to the Texas market. DLR will help Oncor continue to deliver reliable service to all of its customers and continue to drive the economic growth in the Oncor service territory.
“Technologies like DLR give transmission owners like Oncor significantly increased visibility and flexibility to operate more reliably and efficiently,” says Tip Goodwin, DLR project manager at Oncor. “That’s important not only for our residential customers, but also for the more than 400 communities we serve who are looking to grow existing businesses and attract new businesses. While electricity infrastructure may not receive the headlines that tax incentives do, economic and reliable electricity is at the top of the list of priorities for businesses.”
The Nexans DLR technology employs an algorithm that transforms real-time sensor data into a conductor temperature and calculates the maximum current capacity – the Dynamic Line Rating – which maintains the overhead line sag within safe clearance limits. The DLR is updated every 5-10 minutes, providing operators with much clearer visibility than both traditional Static Line Ratings, which use pre-determined weather assumptions, and Ambient-Adjusted Ratings, which take into account the ambient air temperature.
“The SGDP Project has been a complete success, having demonstrated that Dynamic Line Ratings are a practical and efficient tool to increase the capacity of a transmission line, which will enable transmission providers and system operators to mitigate congestion, increase system reliability and redeploy capital to its most efficient uses through a least regrets strategy,” the final report notes.
Oncor was evaluating DLR as a potential key component of its 5-year capital investment program that will average $1 billion per year. The program’s strategy is to invest in technologies and equipment to improve reliability and efficiency of the company’s infrastructure.
“Our investment program is not about just adding more infrastructure. We want to be able to use our existing assets more efficiently and effectively because that’s a more economical use of our investment dollars. DLR clearly demonstrated that we could improve the efficiency of our existing assets in an economical manner,” says Jim Greer, Oncor CEO. “Already we are looking at other areas of our grid where we can install this capability for future investments. This is good for Oncor, the state grid, and ultimately, all of the customers we serve.”
As evidence of the extensibility of DLR technology, in June 2013 Oncor deployed additional DLR systems in the Odessa-Midland region of Texas in a commercially funded follow-on project.
Conclusions highlighted in the report
- Increased line capacity: DLR provided up to 14% additional capacity above the Ambient Temperature-Adjusted Ratings. The incremental capacity was available 83.5-90.5% of the time.
- Reduced congestion: The project found that 5% additional capacity could relieve congestion by up to 60% on the target lines with DLR installed, while 10% additional capacity would practically eliminate all congestion on the target lines. Congestion on the Oncor transmission lines in 2011 and 2012 cost more than $148 million and $197 million respectively.
- Market integration: The integrated Dynamic Line Rating (iDLR) system at Oncor feeds real time conductor ratings to ERCOT, the market operator, who then incorporates the additional capacity into its Security Constrained Economic Dispatch process. With zero operator intervention, DLR capacity is used to increase market efficiency.
- Transmission planning: By providing additional capacity on transmission lines where a full upgrade cannot yet be justified, DLR can be utilized in the planning process to enable a least regrets capital strategy.
- Best practices: The project authors have developed a guide to assist other transmission owners who are considering DLR technology for their own systems.
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