Placing Small Cells on Wooden Electric Distribution Poles

May 16, 2017 —

By Don Bishop

Executive Editor, AGL Magazine

Making the best use possible of space on its wooden poles, Seattle City Light helps wireless carriers place small cells in Seattle. With the use of street lights to support small cells increasing, the utility has a process for replacing existing street lights with hybrid street lights that include antennas and cabinets for small cells.

 

A small cell with two antennas above the communications space and an equipment cabinet below the communications space.

For Seattle City Light, a small cell has one or two small antennas located above the communications space on a utility pole. It has a cabinet placed below the communications space. A small cell is connected with a mobile communications network core with fiber-optic cable. That’s the description given by Doug Haberman, the utility’s wireless collocation program manager, as he spoke about small cells on wooden poles.

On some electrical transmission poles, small cell antennas are placed in the middle, below the high-voltage lines, with the cabinet positioned below the communications space. Sometimes multiple lines of fiber-optic cable share space on the poles.

Seattle City Light also has small cells on distribution poles in residential neighborhoods.

Haberman said that in 2014, the utility had about 40 small cells on its infrastructure. At the end of 2016, the utility had 700 small cells either in operation or in various stages of construction.

Possible Wood Rot

Haberman said that another problem with pole extensions has to do with rot. “It’s hard to tell from the ground whether the pole is rotten,” he said. “Many times, a pole will rot at the top, first. So, sometimes it’s just easier to change the pole out, and then you might as well go with a pole-top antenna installation.”

Not a big fan himself of using shrouds to conceal small cell antennas, Haberman said many jurisdictions are eager for shrouds. “I hate shrouds,” he said. “It’s a lot easier to access the antennas. I’ve been arguing, let’s try to get away from the shrouds, when we can. Shrouds have the benefit that they cover all the wires that don’t show up in the photosims, for some reason.”

Seattle City Light has small cells on distribution poles in residential neighborhoods. The antenna is below high-voltage lines.

In a move that Haberman said is rare for a utility, Seattle City Light allows placement of antennas in the supply space where an electrical transformer might otherwise be placed. He said if the space is available, the utility will use it for a small cell, if it works for the wireless carrier. But he said the utility doesn’t hesitate to take back space granted in the supply space if the space becomes needed for a transformer. The wireless node goes away, and then it’s a matter of finding another place for it on the utility’s infrastructure, if possible.

Equipment boxes and antennas can be installed by different companies. Haberman said the utility generally installs antennas placed above or between high-voltage lines because qualified line people must do the work. He said the cabinets can be installed at a different time by a communications company, and they can be installed while they’re installing the fiber. “We’re working on one now where we’re doing the antennas. They’re going to go back in and do cabinets. And then, whenever they can get the fiber done, we’ll hang fiber.”

Power Disconnect Switches

Seattle City Light requires small cells to have power disconnect switches. Haberman explained that the utility has to be able to turn the small cell off immediately in case of an electrical emergency or a car-pole collision, for example. He said it isn’t possible to take the time to call a network operations center and wait for the small cell to be powered down.

Pole extensions, such as this one, didn’t prove to be as useful as expected. More often, poles are changed out for taller poles to fit small cells.

Also, depending on the jurisdiction, Haberman said the electrical inspector will want to see an external disconnect switch. “I see a lot of poles and street lights that don’t have that,” he said. “I could not get away with that in my jurisdiction. It’s a national code.”

Because the utility requires everything to be in one cabinet, the installer placed a shroud around both units. Haberman said he gave credit to the wireless carrier for using a disconnect switch below the shroud that’s half the usual size for a switch. “They were able to work with the jurisdiction and the electrical inspector to come up with a smaller disconnect switch,” he said. “Everything is smaller. Everything is a little bit less intrusive.”

Leasing

If each of the 700 small cells on Seattle City Light infrastructure had its own lease, Haberman said that would mean writing 700 service-level agreements (SLAs). He said pole-attachment agreements come closer to representing what’s involved with small cell placements, but common utility pole attachment agreements normally don’t mention wireless communications and radio-frequency energy. As a result, the utility uses leases that are somewhat of a hybrid of SLAs and pole-attachment agreements.

Haberman recommended that small cell leases should define the start date for that antenna and should not tie the date to construction. A utility’s real estate department is unlikely to know when the site was built, so he said tying the lease start date to construction would result in inaccurate payments.

Small Cell Future

Seattle City Light’s first hybrid street light includes an antenna and cabinet for a small cell.

The next big thing, Haberman said, is the use of street lights for small cell placements. Haberman said installing street lights for small cells presents a difficulty, because the utility has 40 styles of street lights in Seattle. Also, the utility won’t allow wireless carriers to use the street light power circuit to provide electricity for their small cells. “Our street light circuit never was designed for customer use,” he said. “The wire size isn’t big enough. So power has to come in from some transformer somewhere.”

In the downtown area, Haberman said any street light to be used for small cell placement has to be a replacement. He said street light replacements take time because of the digging required. Also, the small cell owner or installer has to obtain a right of way permit. Based on national code, power to the site has to be separated from the communications connection, and Haberman said that means each pole has to be specially designed. Additionally, fiber-optic cable has to be extended to the site underground.

“So, street lights are challenging, but we’re working on it,” Haberman said. “It’s the future. I get it. But it’s not fast; it’s not quick.”

Seattle City light began locating wireless antennas on high-voltage transmission towers in 1998. Since then, it has expanded into the use of its wood-pole distribution system. The utility accommodates a wide variety of installations from small cell deployments to more traditional site builds on high-voltage and communications towers.


Doug Haberman spoke at this year’s AGL Local Summit in Seattle. For information about AGL Local Summits, visit www.aglmediagroup.com.

 

 

 

 

 

 

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