Bluebonnet Electric Cooperative reaps the benefits of a new single-phase vacuum recloser installation, while reducing environmental impact.
Before Purchasing New Reclosers, Bluebonnet Electric Cooperative (Bastrop, Texas, U.S.) carefully considered all the options. At the time, oil-filled reclosers were installed on its system, which includes more than 11,000 miles (17,703 km) of distribution lines within 14 Texas counties. After a thorough review, the utility chose the Versa-Tech oil-free reclosers from Hubbell Inc. (Orange, Connecticut, U.S.) for their versatility and easy programming, as well as several other features.
With the addition of a vacuum interrupter, Versa-Tech reclosers require limited routine maintenance. The manufacturer recommends a battery changeout every eight years. This met Bluebonnet's desire for a maintenance-free recloser.
Limited maintenance was important to the utility because of the industry shortage of linemen and field personnel, which leads to the obvious challenge of having to do more with less.
Bluebonnet's member base is growing, and some areas of its service territory are becoming more urban than rural — with members who are accustomed to and expect a high level of reliability. The utility's response is to strive for greater efficiency by maximizing productivity. Versa-Tech reclosers support this effort through design and functionality. The reduction in installation and maintenance man-hours allows field personnel to allocate a greater portion of their workday to completing other tasks.
Safety is important in all aspects of a utility's operation, and the Versa-Tech recloser had one safety issue. The recloser has a skirted polymer-insulated support that houses the vacuum interrupter. All components are energized to system potential, and a polymer post-insulator electrically isolates the "live tank" unit from ground. Bluebonnet concluded that if it loses a ground on a traditional recloser, its tank can become energized, as well. Furthermore, Versa-Tech's live tank increases the life expectancy and reduces the maintenance and weight of the recloser.
The utility is making an effort to minimize the safety concern through general awareness and training, just as it does with any other product. Hubbell also has been proactive in providing "Energized Equipment" signs with the purchase of the recloser to warn linemen of the energized tank.
PROGRAMMING AND INSTALLATION
The Versa-Tech recloser is easy to program. To date, Bluebonnet's linemen have not had any problems with programming, because it is simple and straight to the point.
The scratch pad feature within the programming allows the utility to keep notes on each recloser and access those notes when communicating with a device. Bluebonnet stores its map references, pole locations, settings, feeder names and special notes there. With the embedded RF radio and scratch pad feature, the utility can identify a specific recloser at a location where multiple reclosers are installed. Each recloser also stores data on up to 40 overcurrent operations, making it easier for Bluebonnet to maintain its system.
The recloser's design allows for a clean, uncongested pole top in both single- and three-phase applications. The recloser can be mounted on a pole through an insulated standoff or underneath a crossarm with a polymer insulator. The unit's light weight reduces lineman fatigue and construction time.
An additional advantage that this recloser provides is the potential for inventory reduction. As Bluebonnet moves toward installing more Versa-Tech reclosers on its system, the utility will not have to stock as many sizes and types of reclosers. The 30-A to 800-A minimum trip gives the utility adequate versatility to use the device in almost any application on its system.
Although Bluebonnet's service territory is both rural and urban, it is becoming more urban as more development occurs. When load on any particular line becomes too high, the utility converts the line to a higher voltage. The Versa-Tech recloser fits right into this aspect of Bluebonnet's operations.
By increasing the circuit voltage, the utility decreases line current and can increase the load on that circuit. Its other option is to upgrade the circuit conductor, but doing a voltage conversion is typically less expensive than upgrading the conductor under certain circumstances. So, at 7200 V, if the utility maxed out its capacity on the conductor, it could increase line voltage to 14.4 kV and cut its current by half, which would give it more capacity to add load on the conductor in place.
Bluebonnet must change out the distribution transformers in preparation for a voltage conversion, but since the Versa-Tech reclosers will work for both voltages, the utility won't have to change out the reclosers. This will reduce costly labor hours and increase the utility's overall efficiency.
In June 2008, Bluebonnet changed the voltage on one of its lines from 7200 V to 14.4 kV. The 5-mile (8-km) line serves about 200 members. Prior to the voltage conversion, the Versa-Tech reclosers had been programmed at the minimum trip settings for 7200 V. During the conversion, it took technicians about 5 minutes to reprogram the three reclosers on the line to 14.4-kV minimum trip settings. The utility was excited about that, since it performs about 10 or so conversions every year.
When a utility purchases electronic equipment, it usually provides more functions and features than are used on a daily basis. The unused functions, however useful under the right circumstances, are not needed on a daily basis and are rarely used by the utility. With Versa-Tech reclosers, Bluebonnet finally got something that fits the bill. The reclosers have positively met the utility's expectations for a device to replace the standard hydraulic oil-circuit recloser. Folks at Bluebonnet have even recommended this product to other utilities.
This recloser has a provision for cold-load pickup. When a line is energized, it can draw enough inrush current to exceed the minimum trip setting. The cold-load pickup feature prevents the recloser from tripping for a predetermined amount of time after the first manual reclose, after the device has gone to lockout. The amount of delay is set in the programming portion of the software. This delay allows the cold-load inrush current to naturally diminish without tripping the device.
Bluebonnet faced a situation during Hurricane Ike where a Versa-Tech recloser operated to lockout because a tree fell on a line. The utility's linemen picked up the wire, cleared the line and closed it right back in. The recloser operated as expected. Since the devices are fairly newly installed on its system, Bluebonnet expects that winter weather and spring storms will show more of what this device feature can do.
The poly insulators on the recloser are also a plus compared to porcelain, because they are less likely to be damaged during installation or by acts of vandalism. Poly also contributes to the unit being lighter than traditional reclosers.
The lockout beacon feature gives a clear indication when the recloser has interrupted service. A digital record of operations counts is displayed in a window next to the beacon. The color-coded manual operating handle and nonreclosing lever are clearly marked. The LED lockout display enables Blue-bonnet's field personnel to recognize that the recloser is open from a distance, even in daylight.
Bluebonnet is doing its part to preserve the environment and reduce the impact that oil and synthetic materials have on wildlife, people's health and the well being of the planet in general. The Versa-Tech recloser is helping the utility accomplish these goals. From the utility's perspective, this recloser is more environmentally sound than the old oil-filled device, so the utility is operating in a cleaner fashion. There is no oil in the Versa-Tech recloser, and the device itself is smaller, so there will be less to recycle in the end. Bluebonnet is trying to reduce its use of man-made materials and make a positive impact on the communities and habitats it encompasses.
THE WISH LIST
While the experience of installing and operating Versa-Tech reclosers has been mostly positive, there is always room for product improvement. Bluebonnet's list is actually quite small and certainly a lot shorter than the list of advantages for using these reclosers.
The recloser's 400-A continuous rating is sufficiently high enough to suit all of the utility's distribution needs, except when it gets close to a substation. For higher currents, the utility still uses one of the more costly and complex electronic devices. It looks forward to Hubbell advancing the next generation of its Versa-Tech recloser to cover this application, too.
On the programming side, although the utility cannot increase its minimum trip setting in 5-A increments, it can be done in 10-A increments, which is manageable. Bluebonnet was told this would be addressed in a program upgrade.
Also, the utility would like to see the recloser communications support DNP protocol, so it could receive open/close indication and have supervisory control. The utility understands that this is on the product development road map.
A SUCCESSFUL START
Bluebonnet's transition from legacy oil-filled reclosers to the next generation of recloser is going very well. It began installing the Versa-Tech reclosers in May 2008 and has already seen advantages from using this equipment. Benefits include reduced maintenance, easy programming and versatility. While some of these may seem like small advantages, when added up and compared to the traditional oil-filled device, this recloser definitely comes out on top.
If the Versa-Tech reclosers live up to Bluebonnet's expectations, the utility will entertain the idea of replacing its existing hydraulics-based reclosers with these newer reclosers.
Phillip A. Ellis (firstname.lastname@example.org) is the substation and transmission superintendent at Bluebonnet Electric Cooperative, which he joined in 2005. Previously, he worked as a mechanic, lineman and foreman at Red Simpson Inc., an electric utility contractor.