Hurricane Sandy caused significant damage to Public Service Enterprise Group’s (PSEG, NYSE:PEG) high-voltage electric transmission system and switching stations, with the storm’s tidal surge damaging some 13 switching stations and taking 49 high-voltage transmission lines out of service.
Company officials called the nature of the storm’s damage “unique.”
“We not only got dumped on from up above and the wind, but we got a lot of huge surges and subsequent flooding that we were not anticipating,” Esam Khadr, director of electric delivery planning for PSEG’s Public Service Electric and Gas (PSE&G), told TransmissionHub Nov. 2.
Flood waters carrying a significant amount of dirt, mud, and debris inundated PSE&G’s high-voltage transmission and associated equipment including relay racks and motors for pumping plants, causing major damage.
“It impacted all of our transmission-level stations – the 345-kV, 230-kV, and 138-kV,” Khadr said.
Most of the physical damage was incurred by the switching stations, “but once you lose a switching station, you take out all of the lines with it,” Khadr said, noting that a few high-voltage lines did suffer physical damage from wind, fallen trees, tree branches, and other storm-related incidents.
Underground lines not immune
PSE&G’s underground cables were among those hard-hit by the storm. Those cables are inside pipes surrounded by dielectric fluid that is circulated, or oscillated, to remove built-up heat and give the lines greater ampacity. Motors inside the switching stations that circulated the fluid were damaged by the tidal surges, resulting in a host of related problems.
“Without oscillation, you cannot go back and energize those cables right away,” Khadr said. “You’ve got to make sure that there is no gas trapped inside the dielectric fluid, make sure that no water got in. It’s a process.”
PSE&G’s 600 crewmembers, augmented by about 1,500 workers on mutual aid from other utilities, have been working around the clock, “and we’ve been restoring almost all of the substations with the exception of about two at this point, and many of the lines,” he said.
Working on underground lines requires some skills that differ from working on overhead lines, but the utility has employees with those skills, as well as contractors who have been working on reconductoring the underground circuits and building new underground circuits.
Reenergizing transmission lines includes a number of challenges, including maintaining voltage stability.
“We worry about voltage that is too high as well as voltage that is too low,” Khadr said.
In addition, a sizable portion of PSE&G’s cable has capacitive charging. Khadr said the capacitive charging “could cause high-voltage conditions that could impact our facilities [as well as] customer equipment” when lines are reconnected if proper procedures aren’t followed.
At its peak, the storm left some 1.7 million of PSEG’s 2.2 million customers in New Jersey without power, Ralph Izzo, PSEG’s chaiman, president and CEO said on the company’s 3Q12 conference call Nov. 1.
While it will take awhile to get all the lights back on, Khadr said, “We are very confident that we’ll be able to restore our system within seven to 10 days.”