“Because feeders usually are on poles along street right-of-way and are easy to access, they are not buried,” Whiteford said. “The problems in areas we convert relate directly to heavy tree growth and difficulty accessing rear lots.”
Laterals are buried in front right-of-way, usually within 8 feet of the curb.
“We place a 2-by-2-by-3-foot, pad-mount transformer every three or four houses,” Whiteford said. “We directionally drill services to each house and replace existing meters with RF meters, which are read from the street. When a neighborhood is complete, we never have to go in the back yard again. All future repairs can be made in the front. Whether the access service point is a transformer or flush-mount pedestal, repairs are much quicker with less impact to the homeowner. No worry about downed lines. No locked gates. No dog bites.”
During planning stages of the reliability-enhancement program, PSO evaluated neighborhoods to identify the best candidates for replacing aerial lines underground.
“Most of those selected,” he said, “are older neighborhoods, usually with many old, large trees. In looking at the process we identified between 700 and 800 miles of overhead distribution cable that converting to underground would have a significant impact to improving reliability.”
Criteria considered when targeting areas were the following:
• Accessibility: Without alleys in the city, back yards can be difficult to access for repairs.
• Terrain: Is it conducive to directional drilling? Planners wanted to use this technique and avoid trenching.
• History of reliability
“For the first underground conversion,” Whiteford said, “we selected an area that was reasonably representative of the city—one where trees were causing problems, but not one of the worst areas in terms of reliability problems. It was a good starting point.”
Considering all factors, Whiteford said PSO is pleased with progress.
“We have converted roughly 65 miles of aerial cable to underground,” he said. “And we believe we are getting better at it as we proceed. Engineering is more nailed down. Contractor crews are more efficient.”
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