Installing and replacing underground connectors used to be a hassle for T&D Solutions, a contractor with Sharyland Utilities, an underground utility company in Mc-Allen, Texas. Connectors would often overheat, causing studs and screws to fuse together. As a result, it was nearly impossible for linemen to remove the connector. In addition, linemen had to make sure they had the right model, and then disconnect the wiring and reconnect the units.
To overcome these obstacles, Sharyland invested in 50 Universal Toggle Latch (UTL) underground connectors from Hubbell Power Systems. The connectors are universal, so they work on both 100-kVA and smaller transformers. Linemen simply flip the toggle latch one way for 100-kVA transformers and another way for transformers with smaller studs. This simplifies inventory control and reduces storage space, and linemen don't have to worry that they have the right model in stock.
Ease of Installation
In addition, UTLs are much easier to install than traditional connectors. With the screw-on straight-bar connectors Sharyland previously used, the linemen had to take the wires off, remove the bar, put the wires back in and screw down the fastener. If the transformer stud was bent, the crew would have a hard time tightening the fastener. With the UTL, the linemen just put the clasp over the stud and clamp it down without a screw or bent studs.
In fact, UTLs take less than half the time to install as straight-bar connectors. This not only saves labor, it also reduces outage time by 15 to 25 minutes. This is important to a company like Sharyland, which places a strong emphasis on customer satisfaction.
The UTL also makes it easier to position the 350 MCM wiring, which can be tricky to manipulate. The product is designed with offset holes that run parallel to each other in sets of two, making it easier to place the wires. The UTLs are available in two models: straight-bar units (model UTSB8500L) and Z-bar units (model UTZB6500L). With UTL connectors, the linemen can connect up to eight #6-500 MCM taps and up to three streetlight taps (UTZB). However, the Z-bar units give a little more clearance, allowing linemen to work closer to the transformer.
The fact that the UTSB model has three streetlight taps is also a benefit. With other connectors, the field crews had to bunch streetlight wires together into one opening, whereas this product accommodates this wiring much more efficiently.
Made of high-conductivity, high-strength aluminum alloy, UTLs are available as bare bar or with optional clear PVC covers to protect against incidental contact. They also accommodate aluminum or copper phase wires.
Electrical Performance Without Overheating
UTLs improve electrical performance and prevent overheating. In regular straight-bar connectors, the threads on the connectors and studs do not completely match, minimizing the contact area. This small contact area can lead to overheating. The connecting mechanism on the UTL, however, increases the transformer stud contact interface, because it features threads that are die cast directly into the latch. The entire circumference area makes electrical contact, rather than only a small portion, as seen in most thread and setscrew-style connections.
In fact, independent testing shows that the product operates at about 10% lower temperature than slip-fit connectors. This lower operating temperature can be especially important in hot climates, such as along the Rio Grande.
In the past, field crews have had problems with connectors overheating and creating outages. Sometimes, the transformer lug would corrode off, and the linemen would be unable to remove the connector. As a result, the linemen would have to replace the entire transformer. Because this product makes a better connection, overheating is no longer an issue. The connectors are also more likely to outlast traditional products due to this lower heat concentration.
Although UTLs are a bit more expensive upfront, the total cost of ownership is less because of the improved efficiency and ease of installation. Sharyland's crews would take the UTL over a traditional connector any day of the week.
Jesse Acosta ([email protected]) has served as a foreman with T&D Solutions, McAllen, Texas, for four years and has more than 11 years of field experience.