Commonwealth Edison Co. has been looking to the future for more efficient ways to service its 5,400 circuit miles of overhead transmission lines. Many of these lines are installed on a single pole with dual circuits, and it's not feasible to de-energize both lines. Therefore, many pole repairs require linemen to create temporary connections while repair work is being performed.
In the past, line crews would install temporary poles so customers didn't lose power during repair jobs. Unfortunately, this method of switching and rerouting power proved to be extremely time-consuming. Even more, ComEd anticipates that the process of getting lines out of the system will become increasingly difficult in the coming years. Because of these issues, ComEd started looking for alternative methods to de-energize one line and keep the other energized during maintenance work.
Doing the Research
ComEd first started discussing ways to improve efficiency at the 2009 ICUEE show in Louisville, Kentucky. The utility explained the situation to Diversified Products, a company that offers specialized equipment solutions for the utility industry. During the discussion, Diversified recommended one of its products that could meet the task at hand.
Diversified's solution for ComEd was the ELL-161kV energized line lifter. This 10-ft-long insulated jib would let linemen take one line out of service while lifting and keeping another line energized with the jib.
The ELL-161kV has a lift capacity of 2,500 lbs, which allows it to pick up energized lines when poles are spaced far apart. Furthermore, its angular adjustments accommodate diverse applications, and it installs easily to any crane or derrick so line crews can get to work quickly. The unit also has been field-tested and exceeds the applicable requirements for dielectric testing, ANSI A10.31 and ASME B30.5.
Besides the ELL-161kV, ComEd considered other alternatives. However, with Diversified's product, there were no moving parts and linemen could simply use hot sticks to adjust the lines.
After further discussion with Diversified about the product's capabilities and benefits, ComEd realized that the ELL-161kV was not only capable of getting the job done, but it was also the most cost-effective solution. At this point, ComEd decided to purchase three units so linemen could work on multiple phases at one time.
The new products were first put to use when a line crew was sent to replace the crossarms of a wooden pole. Instead of installing a temporary pole or using other methods to reroute the power, the linemen successfully used an ELL-161kV to lift one line and keep it energized while the other line was taken out of service. As a result, customers never lost power, and ComEd got the job done quickly and safely.
Since the first application, ComEd has determined that using the ELL-161kV saves each worker on the job about 10 to 20 hours of labor for every time this product is used. That means a five-person crew could save up to 100 hours of labor. Also, considering a typical work day is 10 hours, a crew can complete a repair job one or two days sooner than if the workers installed a temporary pole, rerouted and switched power flows, performed work on the existing pole, and then restored everything back to normal after the repair was completed.
Looking to the Future
After using the ELL-161kV to help repair the crossarms, ComEd has used the unit only a handful of times. This is only because ComEd recently created a new overhead transmission organization, and in the transition, the company is training 53 overhead transmission linemen. For 2011, ComEd plans to train all of the linemen to properly and safely use the new jib so it can be used much more frequently.
As the linemen get trained and qualified on all of ComEd's equipment, the ELL-161kV will play a larger role in pole maintenance. Likewise, it will continue to save many hours of labor and greatly increase the company's efficiency and productivity. Furthermore, ComEd is currently engineering and developing a single three-phase insulated jib with Diversified.
Vito Martino (firstname.lastname@example.org) is transmission director for ComEd, a unit of Chicago-based Exelon Corp.
Commonwealth Edison Co. www.comed.com
Diversified Products www.diversifiedproduct.com