By William Atkinson, T&D Electrical World,
November/December 2001, Vol 215 . No.6

Alan Drew, vice president of Northwest Lineman College in Meridian, Idaho, comments, "No one wants their power cut off these days, so more and more utilities are opting to engage in energized wire stringing."

Even with the many energized wire stringing projects out there today, Drew predicts even more in the future, because utilities want to squeeze as much capacity as possible out of existing lines to remain viable in the competitive environment. Keeping the power on helps in this regard.

Safe stringing strategies

Drew outlines some strategies to ensure safety during energized wire stringing projects. He points out that there is no substitute for comprehensive planning. "Look at all the potential hazards," he suggests, including nearby road traffic, adjacent lines, and defective stringing equipment. "A good [‘tailboard’ meeting] ahead of time is very important," he continues. "Everyone needs to know the safety hazards, how to perform their jobs, and how to address the hazards."

Scrutinize the equipment next. Drew emphasizes careful inspection of the tensioning and pulling equipment, which provide control over the conductors that will be pulled in. "You also need good stringing blocks on which the conductors will be laid on each pole," he adds. These reduce friction and provide strong positive control. "Good control is necessary to ensure an even pull and avoid jerky [motion]," he explains.

While planning and equipment inspection are important, possibly the most critical element for safe energized projects is good grounding. First, the tensioning and pulling equipment should be properly grounded. "You should also have a rolling ground installed on each conductor as it leaves the conductor reel," states Drew.

Stringing projects usually involve crossing of adjacent hot lines. It is important to install nets over the lines, cover them with protective grounding, and ground on either side of the lines. Another strategy to prevent problems during crossing is to place circuits in non-reclose mode so that if the stringing gets out of control, the circuits will not reclose.

Since most workers involved in a stringing project- the crew members operating the tensioning and pulling equipment, changing reels, and splicing conductors- are on the ground, it is important to provide grounding for them. "All employees should wear rubber gloves when working on these jobs," Drew advises.

One of the best pieces of grounding equipment, according to Drew, is a new product called an equipotential grounding mat, which has been introduced in the last year or so. "Use of these mats will add significantly to the safety of wire stringing projects," he emphasizes.

Drew also points to the importance of constant communication between crews during restringing projects. "You especially need good communication between the people operating the pulling equipment and those operating the tensioning equipment," he reports, so that they can stop and adjust tension properly as the situation requires.

A case in point

Fayetteville Public Works, Fayetteville, NC, has undertaken energized wire stringing projects. According to Jerry Comstock, power-line training supervisor, for the ideal project, you should:

• Get the first conductor pulled in.
• Get the load transferred to the first conductor.
• De-energize the existing conductor.
• Lay that de-energized conductor into a roller to pull in a new phase with it.

Regardless of how the project progresses, the Fayetteville utility takes several safety precautions. "The first is traffic control," explains Comstock. "We do a lot of work along highways, so we make sure we have a way to safely control traffic." Like Drew, Comstock believes another important consideration is careful inspection of equipment and tools. "We use the proper ropes and attachments for the wire-pulling rigs," he comments.

Fayetteville line crews also make sure they use proper cover-up and insulating equipment. When they are pulling a new conductor between existing energized conductors, cover-ups used include rubber hoses and blankets. "We also use rolling grounds on the pulling rigs, where the conductor is on the reel and where the reels are grounded," Comstock adds.