In the aftermath of Hurricane Sandy, crews begin repairing damage to Pepco power lines.
In the aftermath of Hurricane Sandy, crews begin repairing damage to Pepco power lines.
In the aftermath of Hurricane Sandy, crews begin repairing damage to Pepco power lines.
In the aftermath of Hurricane Sandy, crews begin repairing damage to Pepco power lines.
In the aftermath of Hurricane Sandy, crews begin repairing damage to Pepco power lines.

Smart Grid: It's All About Communications

April 1, 2013
Although the new normal may be an increasing frequency of violent superstorms like Sandy, there is no doubt those storms have proved the value of a smart grid.

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.

In the aftermath of Hurricane Sandy, crews begin repairing damage to Pepco power lines.

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.

More Information, Faster Restoration

At its peak, on Monday, Oct. 29, Hurricane Sandy cut power to more than 36,000 Pepco customers, 26,000 of whom were in Maryland. In all, more than 81,000 of its Maryland customers experienced outages at one time or another during the storm. But the utility's hybrid DA system, which encompasses a Silver Spring Networks wireless field area network, operating in the unlicensed 902-MHz to 928-MHz spectrum with backhaul over a public or private wireless system, proved up to the task.

Hurricane Sandy struck on Oct. 29, 2012. The graph shows the number of Pepco (Maryland) customers without power during the superstorm as well as the cumulative outages and cumulative outages restored throughout the event.

There were a total of 42 distribution circuit lockouts, 12 subtransmission line lockouts and 450 downed wire events in Maryland, of which 264 were Pepco wires. The rest were either telecommunications or cable wires, or locations where no downed wire was found, according to Pepco's major storm report. Still, the utility was able to restore service to 95% of its Maryland customers in less than a day, with power restored to all those experiencing outages within 50 hours.

Fortunately, Pepco had updated its outage management system (OMS) software just 10 days before Sandy struck. First, the update made it easier for dispatchers to ping meters in the mesh network directly from within the OMS. Second, because the updated OMS displays power-up messages from those same meters, the utility also was able to use the application to identify nested outages.

Overall, in Pepco's Maryland service territory, 380 events were removed from the queue by pinging AMI meters. Across the Pepco system, a total of 1,092 events were removed from the restoration queue that way, materially reducing the number of truck rolls and helping to ensure crews were dispatched to real outages. Score another one for smart grid communications.

Baltimore Gas & Electric (BGE) had a similar experience with Sandy, even though its AMI and OMS systems were not fully integrated. “We started deploying smart meters around April 2012,” said Kevin Collins, a BGE engineer. The utility had selected Landis+Gyr and GE meters, and a Silver Spring Networks mesh network to collect data from those meters. Backhaul is through a Verizon cellular network.

“Around the time Sandy hit, we had about 130,000 meters installed, about a 10% deployment,” noted Collins. That enabled the utility to implement a manual pinging process in lieu of callbacks toward the end of the storm. “We were able to close out 387 OMS jobs,” said Collins, avoiding additional callbacks and truck rolls. “It made it a lot easier.”

Integrate for Success

Sandy hit PPL Electric Utilities (PPL) hard, but “I think we were the first utility in Pennsylvania to restore power to 100% of its customers,” said PPL Senior Project Manager Mike Godorov. And the reason for that is the way the utility has integrated its smart grid systems — meters, outage management system and geographic information system — to get the greatest benefit.

PPL, which began its AMI implementation in 2004, uses an Aclara power line carrier (PLC) system to bring AMI data back to its substations. From there, an internal interface brings information back to the OMS. “The primary way of getting outage information is from customers on the phone, and we use pings from meters to reinforce that,” Godorov said, noting “there are no last-gasp messages with a PLC system.”

The OMS then determines who is out of service, the extent of the outage and the number of customers affected. “It's helped us significantly in being able to determine where outages are and how far up the line they go,” Godorov added, noting the utility had learned a lot during Hurricane Irene and the October 2011 storm that followed. During those storms, he said, “We had issues with calls, so basically we beefed up our interactive voice-response system and strengthened our call centers, so we're really able to answer calls much quicker and more accurately.”

The system also performed well during Sandy. “The communications systems worked. I'm sure there was spotty coverage at times, but we had enough redundancy in our systems to communicate effectively,” said Godorov. “The whole idea is to be as flexible and redundant as possible.” However, the utility cannot sit on its laurels.

As David Glenwright, PPL Electric Utilities' AMI program manager, relates it, “The Aclara PLC system has served us well over the past decade, but the industry has evolved and developed newer systems with advanced features. We are evaluating various options and will be submitting our final plan to the Pennsylvania PUC in June 2014.”

Fiber Pays Off in Chattanooga

Last summer, when a series of violent, straight-line windstorms, derechos, hit the Midwest and Mid-Atlantic states, a lot of utilities and their customers suffered terribly. But “one utility that had deployed power interrupters every few blocks was able to vastly limit the impact of those windstorms,” said Mark Madden, Alcatel-Lucent's regional vice president for North American energy markets. “Instead of area-wide outages, they were able to isolate them to a block or so, and I think that is one of the major promises of the smart grid.”

That utility was the Chattanooga EPB, which has Alcatel-Lucent's gigabit-per-second passive optical network (GPON) running past every home in the city. As such, Chattanooga may provide a glimpse of what is possible with what Madden refers to as a “substantial communication infrastructure.”

In fact, when the derechos hit last summer, Chattanooga's smart grid, which relies on 8,000 miles of fiber and nearly 1,200 fully automatic switches, proved up to the task and worthy of the investment. “We learned the capability of automation,” said Jim Glass, Chattanooga EPB's manager of smart grid development. Although 35,000 of the municipality's 170,000 customers lost power during the storm, the utility estimates that 42,000 additional outages were either avoided or restored nearly instantly.

Interestingly, when the city was planning its DA system, it considered two different approaches. “Either the switches communicate with each other, or they communicate with a computer in the back office that then issues commands,” Glass explained. EPB chose the former. “If we had gone the other way,” said Glass, “we would have spent a tremendous amount of time with a vendor building the central brain that would issue all those controls. So, it would have been at the end of the two-year construction project before we saw any benefit.”

Instead, he noted, “we started having successful DA events three months into the project while continuing to build out the system, and we were getting more and more benefit as we added more switches.”

The Promise of the Smart Grid

Although the new normal may be an increasing frequency of violent superstorms like Sandy, there is no doubt those storms have proved the value of a smart grid. But as Alcatel-Lucent's Madden noted, “While smart grid technology offers utilities the opportunity both to improve reliability and to reduce the impact on consumers, the extent the smart grid can be deployed and its success is almost entirely dependent on the capabilities of the communications systems.”

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