TOWER RELOCATION – ALBERTA, CANADA
A Canadian electrical power utility company in Alberta had a problem along its 240kV, double circuit, 2 bundle 477MCM ACSR/SD Hawk transmission line. Two towers that were situated on opposite sides of a steep coulee were at risk of collapsing because erosion of the sides of the coulee was beginning to encroach upon the foundations of the towers. These two 45m towers, spanning 569m, had to be relocated to solid ground away from the edges of the coulee. The challenge facing the Utility was how to move these towers without interrupting service. A service interruption would not only be disruptive to subscribers, it would also result in loss of revenue as well as potential penalties. The use of special equipment to hold the conductors would be a very costly alternative and the difficult terrain in the area, together with the prevailing high wind conditions, would make this option very difficult.
After considered evaluation, the Utility decided to use temporary towers to support the live lines while the tower relocation work was being carried out. After a comparative study of the temporary towers available on the market, the Utility decided to acquire Tower Solutions’ towers. These towers were the strongest available, and had a broad range of features making them safer and easier to use as well.
First, two 45m temporary towers were installed alongside each of the two main towers. The live power lines were transferred to these temporary towers, without disrupting service to subscribers. Then the main towers were dismantled and relocated to their new foundations. Two work crews, each consisting of four line workers and a boom truck, installed the four temporary towers in less than two days. Once the base was installed, a column length of 11 sections was assembled in the horizontal position. Guywires and insulator attachments were then installed at predetermined locations on the tower before it was raised. The tower was then raised to the vertical position using a boom truck. The guywires were attached to anchors that had been put in place by the crew. Weeks later, when the main towers were ready on their new foundations, the four temporary towers were removed and placed back into storage. Dismantling of these four towers took only 90 minutes!
One of the challenges facing the crew was the difficult topography in the area. This made it necessary for one of the temporary towers to be anchored at a distance of only 15m from its base, which resulted in an unusually steep guywire angle of 750. Moreover, the area was blasted with unusually high winds of 110 km/hr for extended periods. But despite these extreme conditions, the towers held firm, performing flawlessly. The project was completed on schedule and no one had to tolerate a power disruption.
The Utility was very pleased with the performance of these temporary towers and the cost savings that was generated. In fact, the cost savings generated by the towers exceeded the cost of the towers themselves. This means that the towers were acquired at no cost.
Tower Solutions is proud that its towers were part of this challenging project.