Alabama Power's linemen installed about 815 reclosers over the past three years with funding from the government stimulus. For every recloser the utility has installed, the linemen also are installing Hubbell BP3 switches.
The utility, which is part of Southern Company, decided to invest in the Hubbell switches for both safety and operational reasons. The workers need a source and load side disconnect switch for each recloser. If the wire should fail, then they must have a visible opening so they can work on it easily.
Trying a New Approach
With most of the poles close to the road in Alabama, the utility needed a way to improve safety for its field workforce. In the past, linemen installed regular bypass switches in a wraparound cluster but this presented problems. In that configuration, one switch faces the flat, smooth right-of-way, one switch faces the road, and the third switch faces the ditch or is next to a fence. In some circumstances, this configuration can make operating the switches a real challenge. Standing in the road can be hazardous and climbing over a fence is not easy for the linemen.
In comparison, the BP3 switch has a straight mount with all three switches facing the right-of-way. When the linemen need to isolate a line, they can operate the switches quickly from one position. They are not in the road or the ditch, which improves safety.
Some linemen still like the idea of having a single insulator disconnect for each phase. At Southern Company, however, the field professionals were given a choice, and they selected the BP3 switch, which now has been incorporated into the company's recloser standard.
Alabama Power has been installing the BP3 for more than a year and currently has more than a 100 switches installed on its 15-kV, 25-kV and 38-kV systems. The company is starting to see the advantages of having “three switches on a stick” versus “three switches on a cluster.”
The BP3 comes preassembled and is easy to lift, so installation is quicker and easier than a cluster of switches.
The latest BP3 design is a “center pick.” A lineman can connect one hook to the BP3 and lift it up to the pole, and no slings are needed. A second lineman is usually already in the material handler bucket, so he can drill two holes 18 inches apart in the pole. All the lineman has to do is land the switch and put the bolts in place.
The BP3 weighs about 250 lb, which is not a problem for the field workforce, because the linemen often use a material handler truck and the boom is rated for 750 lb.
Installation takes about 30 minutes, which is about one-quarter of the time it used to take the linemen to install three separate switches on a cluster mount.
Easing the Reconfiguration Process
Having all the switches in a row makes reconfiguring the jumpers simpler. Typically, a recloser has a bushing facing toward the source and a bushing facing toward the load. In some cases, however, it's necessary to reverse that arrangement to meet the company's system requirements. With the BP3, Alabama Power doesn't need to move the reclosers. Instead, all the linemen have to do is move the jumpers on the switch.
In the end, it makes it easier for the linemen to reconfigure the lines, saving time and money out in the field. It also improves the safety in the right-of-way for the field workforce.
Robert Cheney ([email protected]) is the team leader of the Distribution Test Lab for Alabama Power, which is part of Southern Company. He has been with the company for 37 years and has helped to write the material and design specifications for reclosers and the gang switch for Southern Company.
Alabama Power | www.alabamapower.com
Hubbell Power Systems | www.hubbellpowersystems.com