Colorado Springs Utilities is not the only utility to make energized work methods a part of line workers' daily routine. For the last two years, line workers from Northeast Utilities (NU; Hartford, Connecticut) have followed a program for working on energized 115-kV and 345-kV transmission lines in Connecticut and Massachusetts service territories.

The increased demand for power made it challenging and at times impossible for line crews to schedule outages to perform required maintenance. As a result, NU partnered with EPRI to begin looking at methods allowing line workers to perform maintenance while the lines are energized. NU and EPRI spent several years researching and field testing two methods for live-line work: the insulated tool method (hot sticks) and the bare-hand method. A cross-functional core team of the original working group — comprised of line mechanics and employees from the line department, management, safety, training and transportation — concluded the bare-hand method presented a much-more workable solution for maintenance problems encountered in the field.

The live-line core team also evaluated live-line working tools and techniques such as fall protection, pole-top rescue and overvoltage control. While preparing for certification, the NU linemen learned how to maintain their equipment and employ the best work methods.

In the summer of 2008, the first group of live-line workers was certified by Power Line Consultants of Ontario, Canada, to work on live transmission conductors. A key part of this initial round of training included emphasis on safety and the principle of working in an equipotential zone — the physics that allows a bird to land on an energized conductor unaffected by the voltage or current. All parts of a bare-hand worker are raised to the same potential as the live conductor he or she is working on. To maintain this equipotential, linemen wear specially designed conductive suits, complete with socks, gloves and a hood, that use stainless-steel fibers woven into standard Nomex fabric to facilitate the flow of electricity.

Today, NU linemen are using 500-kV-class insulated boom aerial trucks to safely carry out bare-hand work on energized transmission conductors. This new procedure has made it possible to make timely repairs on energized lines without costly line outages.

Reliability has improved as a result of the live-line work, because crews don't necessarily have to wait for an outage on critical lines in order to fix hot spots that develop over time. Significant savings to customers were realized last year through avoided congestion charges on emergent hot spot repairs.

Safety is at the core of the live-line work training. Crews receive annual refresher training, which has increased their skills to include not just repairing hot spots and shunts but also replacing full-tension mid-span and deadend connectors. The live-line work also includes the replacement of crossarms at 115-kV and single-pole replacements on 345-kV wood H-frame structures as well as full H-frame structure replacements on the 115-kV system.

Crews are now working on live lines 80% of the time during the spring, summer and fall months. During the winter months, live-line work is conducted on an as-needed basis.

For NU, live-line work results in more timely repairs, cost savings for its customers and a positive learning experience for its employees.

Laurie Aylsworth is vice president, Transmission Projects, Engineering and Maintenance for the Northeast Utilities system. She is responsible for all field operations within Northeast Utilities' transmission business.