New Bern utility in North Carolina completes transformer replacement

The City of New Bern, N.C., has completed a $1.4 million transformer replacement project.

Work on the Trent Road project began in 2018 and was undertaken because “load growth is an ongoing concern due to our limited substation capacity during peak load times,” New Bern spokeswoman Amber Gray said via email. And, she said, “there is always an anticipation of customer growth.”

The project took around 14 months to complete, Gray said.

Ongoing system improvement was the main purpose of the project.

The project called for the replacement of General Electric 16.667 MVA, single phase units with a total capacity of 50 MVA that were built in 1960 with a WEG 50 MVA with LTC three phase transformer.

Going from three individual transformers to one saves space and “simplifies control and metering cable runs and, on a financial side, costs less for maintenance and repair,” Robbie Allen, electric substation superintendent at New Bern, said via email. And the saved space leaves more real estate for other equipment needed for system expansion, such as circuit breakers, he said.

The new transformer is in a substation that is “at the heart of our system, and this particular bank serves the most load individually out of all of our banks,” Allen said. That and the age of the GE unit were key considerations in choosing the Trent Road site for the replacement project.

Along with the new transformer, New Bern also replaced the old electromechanical relay with new microprocessor relays. The modern relays “give us better capabilities regarding more accurate SCADA [supervisory control and data acquisition] telemetry and fault recording,” Allen said.

In addition, the public power utility replaced the 115-kilovolt (kV) circuit switcher with “a more updated model giving us the ability to receive alarms if the SF6 gas in the interrupters should reach low levels,” Allen said.

The 115-kV tap that feeds the substation was also reworked with new steel poles, which enabled the removal of old wooden poles and the elimination of “a ton of guy wires,” which freed up more space on the property, Allen said.

The reworking of the 115-kV lines “also enabled us to install line switches, which enable us to de-energize certain parts of the substation without de-energizing the rest,” Allen said. “This will enable us (in most instances) to maintain at least one bank in service during most outage situations.”

“We definitely upped our game on SCADA visibility and capabilities,” Allen said. “Not only do we get more accurate analog information, such as voltage and power measurements, but as we move forward, we will be able to have more extensive remote controls on station equipment.”

The next oldest units on New Bern’s system were built in the late 1970s and early 1980s.

They are definitely going to be up for consideration at some point, Allen said.

The utility, in fact, is looking at building another substation to accommodate system load growth.

“After that, I certainly am in favor of starting a similar replacement process on the other bank at Trent Road as well as our Glenburnie Substation,” Allen said. “Hopefully we can continue to move forward with this progress as it only helps make us a more reliable utility for our customers, and that is what it is all about in the long run.”