Rebuilding a Power Line and Improving Customer Reliability

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February 6, 2017

NV Energy is constantly looking for ways to improve and maintain the lines and equipment. Recently company engineers focused their expertise on a legacy 60,000-volt powerline that was built in 1956. To ensure continuing service to customers and necessary environmental protections, the project required out-of-the-box thinking and a multiphase approach.

The Foothill to Kingsbury Line Rebuild
The first phase of this project was designed to maintain and improve electricity reliability for the Heavenly Ski Resort and other NV Energy customers on the east shore of Lake Tahoe. Because of the difficult forest terrain, limited access and environmental concerns, NV Energy crews used a combination of new technology and old technology to replace 50 deteriorating wooden poles originally installed 60 years ago along a three-mile stretch of the 14.8-mile line.

Where possible, NV Energy utilized existing access and road easements for equipment to access the 60 year old line. Where steep terrain made it impossible for backhoes and other excavation equipment to access pole locations, crews armed with old-fashioned shovels and digging bars dug holes for 28 new pole structures. A helicopter flew in new steel poles to each new hole and crews set them carefully in place. The helicopter also delivered new conductor and hardware that were strung on the new steel structures.

To improve the line’s resistance to extreme weather, the design included modernizing the line with fire resistant steel poles and a protective overhead shield wire. The shield wire protects the line from lighting strikes, which reduces lightning-caused fires because the shield wire is carefully grounded and not adjacent to vegetation. The engineers were also able to design longer, higher spans over the canyons because of the steel pole structures, which minimizes the threat of damage from avalanches and falling trees.

During construction of the project, NV Energy used manual switches and back-up distribution systems to assure that customers did not experience any loss of power. After three and a half years of permitting and design, and five months of construction, the $4.1 million line rebuild project was successfully completed and energized. This happened in time for the winter snowmaking season at the Heavenly ski resort.

In 2017, the line will be fitted with a new three-way remote controlled switch. This will give NV Energy the ability to keep the customers at the top of the mountain in service, while quickly isolating parts of the line when maintenance or repairs are required. 

Employees from numerous departments carefully worked together to successfully implement a plan that ensured customer service was maintained, the environment was protected and costs were kept as low as possible.

Innovation and an Emerging Technology
The second phase of this important project took place in the Carson Valley area, which finds the 60-year-old line running through a very shallow water table and areas where ranchers use flood irrigation to water their land. Over time, the wooden poles had rotted and lost their foundation rigidity. Some were leaning at up to a 15-degree angle, which compromised the tightly stretched span of electrical wires.

NV Energy’s team did not want to merely replace the compromised poles with new ones, but researched various strategies and products that would address the soft soil and watery challenges in this area. They eventually teamed with a company called Helical Pier Systems (HPS). The company has a proprietary product called helical piers, which essentially are a large soil screw that anchors the structure approximately 30 feet into the earth.  Typical utility poles are buried to a depth of eight to ten feet and then backfilled around the pole with a specific mix of rocks and sand and then topped with concrete to keep the poles watertight. 

This 3.8-mile section of line originally consisted of 60 wood poles, but the stronger pole and anchoring system enabled the engineers to reduce that number to 54 structures. This reduction of poles allowed the ranchers in this area to regain some of their land and better utilize it for agricultural needs.

From design to installation, this phase of the project took 13 months and more than ten employees to complete and cost $1.4 million.  This investment ensures the structural strength of the poles, which obviously increases electricity reliability to NV Energy customers in the Carson Valley and Heavenly Ski Resort areas.

Additional Line Improvement Benefits
There are two additional features to both sections of the line that will provide benefits to customers and the environment for years to come.  Although the line is currently energized at 60,000 volts, it was built to be able to switch over to a 120,000-volt line in the future when customer needs increase.  Additionally, the distance between the electricity-conducting wires was extended, which help protect large birds such as eagles, hawks and falcons from making a connection between the energized wires.   

It’s all about the Customers
Electric reliability is measured in two main ways – a System Average Interruption Frequency Index and a System Average Interruption Duration Index. The company never rests on its laurels. Rather, company leadership and numerous teams are constantly working behind the scenes to look at ways to improve service to customers and be as efficient as possible in providing that service.  The rebuilding of this important line to NV Energy customers in Nevada is one case in point.

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