For the second year in a row, the Northeastern United States was hammered by record hurricanes and thunderstorms. In 2011, Irene wreaked havoc on the electric power grid, but Sandy, which knocked out power to more than 8.5 million homes and businesses across 21 states, may have been the game changer.
“I think, at this point, it's undeniable that we have a higher frequency of these extreme weather situations, and we're going to have to deal with it,” said New York Gov. Andrew Cuomo. Indeed, with every coastal city from Houston to Boston now at risk, the stakes of the game are clear. And the pressure is mounting to determine how well the smart grid — and particularly the communications system, the central nervous system of the smart grid — has performed under stress and whether increasing investment in the communications system is the answer.
Lessons from Sandy
Truth to tell, prior to Sandy, the federal government invested nearly $4 billion in stimulus funds in the smart grid. But, “there wasn't a lot of smart grid equipment deployed in the area Sandy [most directly] impacted,” said Doug Houseman, vice president of technical innovation at EnerNex. That is a problem with any direct analysis of smart grid benefits. However, areas to the south of New York and New Jersey — particularly Philadelphia, Baltimore and the Washington, D.C. metropolitan area — do offer important lessons.
For instance, said Houseman, where utilities had installed sectionalizers, better relays and other devices that would allow them to reconnect automatically, the geographic areas affected by outages typically were reduced by one-half to three-quarters, and the outages themselves often lasted less than 30 seconds. “We have started to prove that distribution automation can make a big difference,” Houseman noted.
Another important lesson from Sandy, Houseman said, is that smart grid technology can make line truck operations much more efficient. “One utility that had automated a couple circuits for an analysis of relays was able to direct a truck to within 50 yards of an outage, cutting the expected patrol time of 30 to 45 minutes to about 5 minutes,” said Houseman. “In one case, it was able to direct the truck to the exact spot of the outage for a huge increase in efficiency.”
While this helps to make the case for investment in smart grid technology, Houseman cautions that any bump in operational efficiency — and faster restoration of outages — assumes the utility has the ability to get critical data back from its advanced metering infrastructure (AMI) and distribution automation (DA) systems rapidly. That requires the communications system to stay up long enough to get the data back to the control room fast enough to allow controllers to make accurate decisions about the data, and to drive a complete and correct system model fast enough to get good decisions in a reasonable amount of time.
In summary, the smart grid communications system is the foundation on which grid resilience will be built.
Proof of the Pudding
When Sandy hit Philadelphia, a bit more than 10% of PECO's 1.8 million electric customers were connected to the utility's smart grid communications platform, most of which consists of a Sensus FlexNet point-to-multipoint wireless system with backhaul over a privately owned fiber network, supplemented in certain areas with a WiMAX field area network and microwave. That made all the difference, according to Glenn Pritchard, PECO's principal engineer and smart grid technology lead, who said the PECO smart grid system “saved three days restoration time” and some $15 million because of greatly increased efficiencies in managing repair crews.
Pritchard explained, “We have two levels of crews — traditional linemen, or aerial line mechanics, who repair distribution lines, transformers, poles and such, and energy technicians, who work on service drops to homes and meters.” The new smart grid communications system made it possible for the utility to determine which crews were needed where.
In fact, said Pritchard, information from the system enabled PECO to cancel 4,300 single-customer, small-outage calls and 800 distribution line calls. Conversely, the system permitted the utility to escalate more than 1,000 single-customer outage calls from secondary to primary. This is important, he noted, because “if we sent a secondary crew to a site requiring linemen, they couldn't have made the repair, and the trip would have been wasted.”
Underscoring Houseman's point, Pritchard added, “It allowed more effective dispatching.” Of course, to make it all work, the smart grid communications system must be able to take whatever Mother Nature dishes out. “The good news here is that the system has a lot of redundancy,” said Pritchard. Although PECO was not able to communicate with about 30% of its 163 Sensus Tower Gateway Base Station data collectors when Sandy was raging, it was still able to talk to 98% of its AMI meters.
“It was extremely encouraging that we could maintain that level of communication through the storm,” said Pritchard. However, he admitted, “Being the first time through, we did have to cut our teeth a bit.” For instance, he noted, “The primary cause of failure of communication with the towers was extended power outages beyond the 12-hour internal battery life span.” To remedy the situation, PECO installed generators at key sites to maintain critical communications.
Pritchard said PECO invested in the Sensus FlexNet system for its AMI and smart grid field area network for a couple of reasons. First, he said, it allowed the utility to meet the state's timetable for providing smart meters to customers. PECO had already fully deployed a first-generation automatic meter reading (AMR) system, so any AMI meter exchange would have to be fully functional at the time of the exchange (that is, no time lag). “This is unlike most other deployments where the smart meter could be read manually while the network and back-office systems were completed,” he added.
Second, the Sensus system allowed PECO to build the field area network in advance of any meter deployment. “This is unlike any of the competing mesh networks, which require wide meter deployment to ensure systemwide communications,” Pritchard said.
Overall, Sandy taught the utility “to operate more effectively, manage its communications network and to better triage the damage,” said Pritchard. He also noted that neighboring utilities — with different smart grid communications technologies — also performed well during Sandy.