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Explore a solution for managing contingency overloads on a critical power path to optimize transmission in the grid. Learn about possible strategies and case studies for optimal system performance.
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CREZ Optimization Studies:A Possible Solution for Low-Voltage Parallel Paths Cathey Carter, PE RPG CREZ meeting 12/14/2007
The Problem West to North or West to Central transfer studies usually show contingency overloads on the 84 MVA 138kV path between South Abilene and Stephenville. • This line is very long and was state of the art many years ago. • It is one of the sources to the even smaller 69kV load-serving network for Eastland, Callahan, Brown, and Comanche counties.
Possible Types of Solution to this Problem There are 4 ways to solve these low-voltage “local” problems: • Build new big lines to carry the power during the contingencies. • Re-build the existing small lines. • Install protection schemes or FACTS devices to limit the power flows on the small lines. • Rearrange the small lines so they do not form a parallel path to the big lines. This presentation presents an example of method #4.
Changes • 4 new 33 MVA 138-69kV autotransformers with LTCs (like those at Alamito Creek in Presidio). • One 13-mile extension of a radial 138kV line. • Two small 69kV capbanks, such as 3x2.4Mvar • Remove the Putnam phase-shifter and split the 138kV bus. • Open 15 sections of 69kV line, including 3 that are already modeled as normally open in the base case.
Questions and Challenges for Transmission Planners • Do you see a better solution for this area that would allow higher West to North transfers? • for not much higher cost • without decreasing reliability to the load customers • What is your favorite other low-voltage “local” contingency overload? • Where else would you apply this method? • Would you apply this to Saps-Menard-Gillespie? If yes, how? If no, why not? • Would you apply this to Brownwood-Lampasas? If yes, how? If no, why not?