by Lisa Meiman

Or really big football players. Towers grow there, too.

About three dozen steel lattice structures in Upper Great Plains are going through growth spurts this year to raise the energized lines to the appropriate safe distance from the ground.

New technology, adapted from the lifting technique that moves houses, can add several feet to a tower’s height without removing the conductor, needing cranes or involving a significant number of workers and heavy equipment.

From Aug. 5 to 18, UGP completed test lifts on two towers with their Canada-based contractor, AmpJack, to determine if AmpJack’s patented technology is an adequate solution for the other 35 towers in need of a raise.

“We were extremely pleased,” said Upper Great Plains General Engineer Cody Kinsley out of Huron, South Dakota. “By adding in a 5- or 8-foot section to the existing tower, we are meeting our compliance requirements while realizing significant cost savings compared to traditional tower-raising techniques.”

To raise a lattice structure, one jack is clamped to each of the four legs and surrounded by temporary support framing at the waist of the structure. The tower is separated and lifted by the jacks. Then, the new section, designed by Western and built by AmpJack, is bolted into the gap, and the jacks and support framing are removed. “In the end, it looks like the rest of the tower except shiny and newer,” said Headquarters Civil Engineer Cody Neyens, who designed the new sections. Raising one tower takes a crew of five people about two days, including set up, raising the tower and tear down. Western and AmpJack plan to raise towers through September and October. 

This emerging technology is revolutionary for the energy industry, but still has its limitations. “The technology only works for double-circuit steel lattice structures. The structure also has to have the capacity to bear more load,” said Neyens. “These UGP structures did, but that’s not typically the norm. Structures are built for exactly what’s needed.”

Need for growth 

In October 2010, the North American Electric Reliability Corporation released the Facility Ratings Alert, requiring utilities to prove their facility ratings, or capacity at which the transmission equipment operates, were based on actual field conditions—not just design. One of the key limiting factors in facility ratings is ground clearance. 

UGP and most other regions hired contractors with LIDAR-equipped aircraft to map their entire transmission systems from the air. Sure enough, there were several spans of transmission lines that were out of compliance, their conductors too close to the ground at maximum operating capability.   

“There are a number of reasons why spans didn’t have appropriate ground clearances,” said Neyens. “Some of these towers are 50 years old or more; things change. Conductors could have stretched under heavy loading; something in the topography changed, like a farmer could have built a berm or a road had been raised; or survey data was not accurate at the time of design or construction of the line.” 

Western got to work modifying the structures in a variety of ways, including: 

1. Sliding the conductor from one span to another. This was ultimately used as a temporary solution due to the tension imbalance it created at the structure. 
2. Installing floating dead-end assemblies, which, in essence, bend the insulator at a 90-degree angle and then connect the conductor to the end, raising the conductor about six feet.  
3. Excavating the ground beneath the span. 
4. Replacing towers with taller ones. 
5. Reconductoring.

But with more than one-third of the transmission lines and more than one-third of Western’s 1.3 million square-mile territory, UGP had more work than the other regions and was looking for a more efficient and cost-effective solution.  

“From the onset, it was UGP’s opinion that some structure modifications were temporary, but the anticipated costs for structure replacements required out-year planning in the budgetary cycle. At this time, we became aware of Ampjack lifting technique and its potential to solve our problem at significant cost savings” said Kinsley. After a technical review in Canada, UGP knew it had found a viable solution and contracted with AmpJack to provide the same service to lines in North Dakota, South Dakota and Iowa. 

Many utilities and groups are paying close attention to how this emerging technology works out with UGP being one of the early adopters in America. “Raising the towers like this is unique. We’re willing to be a best practice participant for NERC and [Federal Energy Regulatory Commission] and share our experience with others in the industry,” said Kinsley. 

What really gets engineers excited 

Finding inadequate ground clearances was only the most immediate benefit of using LIDAR to record UGP’s 115-kilovolt and above lines. The deliverable for the work was raw data that could be imported into Western’s Power Line Systems Computer-Aided Design and Drafting software, or PLS-CADD.  

Using the LIDAR data, PLS-CADD creates a two-dimensional ground surface overlaid with images and accurate models of the transmission line wire system. An accompanying tower program adds detailed 3-D tower information. The renderings can be rotated on any axis to provide the viewer infinite profiles of the landscape.  

The main benefit is improved situational awareness. “It’s an exact replica of the line,” said Kinsley. “This work used to be done by hand and then digitized. It’s much more accurate than drawings. We can quickly get changes and modifications to the field.” 

Neyens added, “This tool is very powerful. It doesn’t just help with compliance. When we have maintenance issues or storms, we have an exact model of the system. We can tell the field immediately what size towers are needed, where they need to be sited and other information so we can replace and rebuild faster.”

PLS-CADD is also modeling software that can predict outcomes of environmental conditions or help deduce what happened in the past. In June, massive storms took down more than 100 structures in UGP, including 52 structures along a line more than 100 miles long. “Some of those structures were practically new, only being replaced only a few years ago due to severe weather. We wanted to know what is unique about that segment. What is happening there? Can we improve the structures or siting to make sure it doesn’t happen again? This software enabled UGP identify weak points and make system improvements,” said Kinsley.  

“We’re now realizing how many side benefits this tool has. Before LIDAR and PLS-CADD models, UGP would have never used an emerging technology such as AmpJack; there were just too many unknowns.  What started as a NERC alert now has the UGP transmission system positioned for our piece of the energy frontier,” he concluded.

​More photos  available on Flickr.