T&D World Magazine
System Extends Life of On-Load-Tap-Changers in the Field

System Extends Life of On-Load-Tap-Changers in the Field

Many Westinghouse UVTs were placed in service more than 40 years ago, and even the youngest ones have been in the field for more than 25 years. Spare parts are costly and increasingly difficult to obtain. Experts are retiring, and technical expertise is being lost quickly. With the utilization of RMV-II components in the VACUTAP® UVT-LTX, a standardization of the fleet to reliable and maintenance-free tap changers will be the result.

One example is the UVT-LTX retrofit in Florida. One hundred miles south of Miami, energy supplier Keys Energy Services operates the Big Pine substation, home to an old Westinghouse transformer that transforms power from 138 kV to 13.8 kV. The UVT on-load tap-changer on this transformer has regularly required maintenance. The costs and long downtime periods of this regular maintenance caused major problems for Keys Energy Services. The solution: Retrofit with a new VACUTAP UVT-LTX from MR.

The LTX, which stands for Life Time Extension, transformed an old Westinghouse UVT into a new VACUTAP RMV-II. Only the load-switching unit, gearbox and motor-drive unit had to be replaced. The housing, contact board and selector elements of the old UVT could be kept. This also meant that the oil didn't have to be pumped out of the transformer. All in all, this was a low-cost solution for Keys Energy Services, especially since the maintenance interval was extended to 500,000 tap-change operations. Since it is unlikely that this number of tap-change operations will ever be reached in a normal network application such as that used at Big Pine, the tap-changer is now virtually maintenance-free.

MR-Experts from the U.S. subsidiary, Reinhausen Manufacturing (RM), visited the site to undertake the replacement. Under the direction of RM service technicians, the work was successfully completed in under a week. Transformer components were also replaced in the process. The pressure relief device, displays, and dehydrating breather are now from Messko and are therefore guaranteed to be reliable and maintenance-free.

Not far from Big Pine, the RM staff has replaced another VACUTAP® UVT-LTX at the Big Coppitt substation. The tap changers in both substations are now running with proven VACUTAP® technology from MR.

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