National Grid U.K. Looks for Smart Solutions
A fifth of Britain’s generation capacity will close over the next decade because of age and environmental legislation. New low carbon generation is being built to take its place, which requires investment in the transmission grid to bring the energy to load centers and avoid bottlenecks in the network. With the dual challenge of reducing both the impact on the countryside of new transmission lines and the impact on energy bills of this investment, the UK’s National Grid always looks for opportunities to upgrade its existing infrastructure before building a new line.
Installing 3M™ ACCR 1033-T13 Curlew through stringing blocks in a bundled configuration on National Grid’s West Burton to High Marnham 400 kV line.
The intersection of the need for more transmission capacity and the needs of the environment and society have led National Grid to evaluate innovative solutions, including 3M™ ACCR, for upgrading existing lines.
National Grid owns and operates the electricity transmission network in England and Wales, which includes 7,200 kM of overhead lines and 690 kM of underground cable, and operates but does not own the network in Scotland. Overall, National Grid U.K. transmits around 90% of the U.K.’s electricity from both traditional and renewable generation to distribution power companies who serve the country’s homes and businesses.
In 2012, the utility first installed ACCR 1033-T13 Curlew on a 230 kV line at the company’s training school at Eakring, Nottinghamshire, to gain experience with the product. In 2013, National Grid installed approximately 58 miles (93 kM) of the same conductor on a 9.3 mile (15 kM) stretch of the 400 kV, double bundle West Burton to High Marnham line near Retford, Nottinghamshire.
While the installation functions as a pilot to assess the conductor in comparison to competing high temperature, low sag conductors, it also enables National Grid to connect offshore wind farms to the onshore grid without the cost and disruption of modifying or rebuilding existing structures, reinforcing foundations or constructing a new line.
“We worked to aggressive timelines to deliver the conductor and prepare for installation,” said Neil Roberts, 3M’s general sales and marketing manager for electrical and communications markets in the U.K. “We expect that 3M ACCR will continue to play a role in helping utilities address the changing demands on the transmission system.”
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New Video — 3M™ ACCR Corrosion Performance Hawaii Field Test
Recently, 3M released a new video describing a field test in the corrosive salt spray environment of Hawaii. The field test demonstrated the corrosion resistance of its high capacity transmission conductor, 3M ACCR.
3M scientists knew that the all-aluminum composition of 3M ACCR high capacity transmission conductor would make it more resistant to galvanic corrosion than steel and aluminum conductors. The challenge was to demonstrate it to our customers, who are charged with protecting the reliability and integrity of critical transmission lines.
In 2004, a standard salt spray test, using an environmental chamber that complied with ASTM B117-03, “Standard Practice for Operating Salt Spray Apparatus”, was performed by Kinectrics North America, Inc. Test results showed no difference in the performance of the exposed ACCR conductor samples, individual aluminum alloy wire samples, or individual core samples when compared to unexposed reference samples.
See the test report, “Kinectrics North America Inc. Test Report for 3M to Compare the Salt Spray Corrosion Performance of 795-kcmil 3M™ Aluminum Composite Conductor Reinforced to 795 ACSR Conductor”
ACCR Corrosion Performance -- Hawaii Field Test
But actual field conditions often vary from laboratory conditions. So 3M also designed a field test, in cooperation with Hawaii Electric Company (HECO) and the University of Hawaii. In 2002, 3M ACCR 477 Hawk was installed on a 46 kV distribution line on the north end of Oahu. This site was chosen because the sea spray laden trade winds produce a highly corrosive environment. In fact, standard steel core and aluminum conductors typically last only about three years in this environment before showing significant corrosion. 3M left the ACCR installation in place for 11 years. Last summer, after removing it from the HECO line, 3M performed a series of tests on the conductor. First, visual inspection on site showed no signs of corrosion.
Next, we sent the conductor back to St. Paul, where we tested five samples of the conductor using a cable strength tester. Two dead ends with the conductor were also tested. All samples tested in the range of 105 to 107% rated breaking strength (RBS), well above the specified strength. We also measured the conductor weight, and the results showed no measurable changes. Finally, the conductor was disassembled and inspected under optical and scanning electron microscope for signs of corrosion and pitting. Apart from a slight discoloration and darkening of the outside layers, there were no signs of corrosion or pitting. The results of this long-term field test clearly demonstrate that 3M ACCR high capacity conductor has good resistance to salt spray corrosion in extreme, but real, field conditions. For more information, view the video or read the original field test report.
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Join Us at IEEE PES in Chicago
For over 60 years, customers like you have counted on 3M for innovative, reliable solutions to demanding challenges in the power utility, electrical construction and maintenance, and device manufacturing industries.
During the 2014 IEEE PES T&D Conference and Exposition in Chicago on April 14 – 17th, we will be featuring a number of advanced 3M solutions for power transmission and distribution, including: 3M™ Sensored Cable Accessories, which provide accurate voltage and current information from your underground grid, giving you the visibility you need to enhance efficiency and reliability. See www.3M.com/grid.
3M ACCR Conductor, a fast and potentially cost-saving way to increase capacity on existing towers, achieve greater clearances and meet strict reliability standards. Browse this site for more information or visit www.ieeet-d.org.
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