By Jennifer Kelly, NV Energy
There is nothing common about NV Energy’s new Sinatra substation or the miles of underground and overhead transmission lines that feed it.
The substation sits in the shadow of the famous Las Vegas Strip. Sinatra was designed to serve MGM Mirage’s massive CityCenter project, as well as other new developments in the surrounding area.
CityCenter is the largest, privately funded construction project in the United States. Scheduled for completion by the close of 2009, this $9 billion mixed-use resort property will feature 16.8 million square feet of hotel, shopping, restaurant, condominium and casino space.
At 336 MVA, the Sinatra substation brings online enough capacity to serve some 56,000 single-family homes during the hottest summers.
NV Energy built the substation on an inconvenient, 1.6-acre wedge-shaped parcel of land. Such a facility typically requires 3-5 acres for a similar compact gas-insulated design, or 10-15 acres for a less expensive but more spacious open-air design.
Compounding the difficulty level, the substation sits between Interstate 15, which brings millions of tourists to Las Vegas each year, and Frank Sinatra Boulevard, a main artery that brings thousands of employees and tourists into the resort properties each day. Bringing in equipment and workers—plus trenching and pulling underground cable—amid the 24-hour pattern of activity in this resort corridor was a constant challenge.
That was not, however, the only challenge. Completing the project involved boring five 42-inch steel casings under I-15 to pull the transmission cable into the substation. Crews had to drill through calichàƒ©, a rock three times harder than concrete.
The challenges didn’t end there. Near Tropicana Avenue, NV Energy had to drop its transmission line trench from 8 feet deep to 25 feet deep to miss an 84-inch Southern Nevada Water Authority pipeline and two high-pressure jet fuel lines.
The project included two phases. Phase 1 was completed in November 2008 and included construction of the substation with a six-breaker 138-kV GIS ring bus, four 138/12-kV transformers and approximately one mile of 138-kV underground transmission line. Phase 2 was completed in May and included the addition of a new four-breaker 230-kV GIS ring bus, 230/138-kV transformer, a mile of 230-kV overhead transmission line and a 2-mile loop of 230 kV underground transmission cable.
The 12-kV main-transfer switchgear was designed with 24 feeder positions across the four distribution transformers and includes automation logic that will keep all the feeders in service in the event of the loss of up to two transformers.
“It’s really impressive,” said Herb Goforth, NV Energy’s technical services and support executive. “This team tackled many challenges and still delivered this multifaceted $96 million project on schedule and on budget. And they did it with no injuries.”
Jennifer Kelly is manager, major projects—resort corridor, for NV Energy in Las Vegas.