A new smart grid initiative is rolling out at San Diego Gas & Electric, bringing wireless sensors to the utility’s grid that it believes will make its network more reliable and responsive to power outages.
David Geier, vice president of electrical operations for the utility, said in January that the changes SDG&E is making, from the wireless sensors — wireless fault indicators, to be precise — to its other smart grid initiatives, are quickly putting San Diego at the forefront of smart grid implementation.
The purpose of the new sensors is to improve responsiveness to localized blackouts. Mention blackouts to anyone who was in San Diego on Sept. 8, 2011, and some vivid memories are likely to be told.
On that day, SDG&E was in the pilot stages of its wireless fault indicator program. About 50 were in place around the grid. Today, there are about 2,000.
It brings to question whether or not the new sensors could have done anything had they been in full rollout. According to Lee Krevat, SDG&E’s director of its smart grid and clean transportation initiatives, the wireless sensors aren’t exactly designed for such rare, full-grid events.
But they still would come in useful should that happen again. And for more common events, the value of them is clear, he added.
“They said, ‘we’re out,’” Lee said, referring to the information sent to SDG&E from the sensors during the big blackout.
While that may sound like an insignificant piece of obvious information, it meant a great deal to the program.
“While we already knew we were out, because the lights were off, they were able to let us know we were out even though we no longer had power,” Krevat said. That was possible because of the battery back-ups on certain cellphone towers, which are the mechanism by which the information was designed to be transmitted.
The other positive to come from the experience was that the sensors were able to transmit information indicating restoration of power when it did finally start to come back.
The answer to why such information is important when anyone paying close attention to their home’s power might be able to figure that out by flipping a light switch is rather simple. While the big blackout indicated the program was working as intended, Krevat acknowledged that in general, the system isn’t as useful in such a full-scale outage, at least not on the front end.
On the back end, however knowing when and where power is starting to flow back into the grid provides real-time insight into where problems still exist.
More common are the smaller blackouts, though, like when a portion of the grid goes down after a vehicle takes out a transformer in a car accident, or when another problem causes isolated problems. That’s where the system has its greatest impact.
Those sorts of situations require crews to make physical checks of power lines’ fault indicator switches, transformers and other parts of the transmission system to identify the location of a mishap and get to making repairs.
In San Diego, where power lines cross hilly and canyon-rich topography, that means significant time and travel is sometimes required to check one end of a line, the course of the line, and then the other end of it. Once one side is checked, a crew may have to jump back in its truck to drive around a canyon to get to the other side.
During an outage, when customers are losing heat and frustration is mounting generally, that time is significant.
“It could be miles,” Krevat said. “Because they know that the customer who lost the energy is miles away, but they don’t know where (exactly the problem is).”
Since the November 2012 rollout of the utility’s new Outage Management System, the 1.4 million smart meters in the SDG&E service territory can identify the run of line that’s affected by an outage, but the exact location of the problem within that line still isn’t known in those situations.
The wireless fault indicators add to the OMS by avoiding much of that hassle, pinpointing the problem down to a couple of sensors in between the affected smart meters. They won’t replace the practice of performing the physical checks, but they will reduce the portion of the system that requires physical checks, Krevat said.
“So you can see how having data like that is very helpful to knowing what’s going on in the system.”
So far, SDG&E has installed its 2,000 sensors in portions of the grid it deems the most vulnerable, like areas with older infrastructure. By 2017, the utility estimates it may have up to 10,000 installed, but SDG&E said the final number will reflect only what’s necessary to take care of problem areas.
During the big 2011 blackout, there was a problem, though, that limited the sensors’ usefulness: About 30 percent of the cellphone towers were not equipped with battery back-ups to stay alive for a while during the outage, rendering some of the wireless sensor information undeliverable in certain areas.
Krevat said cellphone companies took notice of that when some people reported not having cellphone service from the beginning of the outage, while others had service for at least a few hours into the outage because of the back-ups on their providers’ towers.
“They’re all working on better back-up,” Krevat said.
In the cases of more common localized blackouts, even a few towers without back-up wouldn’t affect the sensors’ value, since the signals go out for miles and would more than likely be able to find at least one tower with back-up.
But even during the big blackout, the immediate signaling from the sensors that power was restored area-by-area saved resources.
“We’d think we turned it on in a given area, but it was very nice to get these signals from the devices saying they were back,” Krevat said. “What we used to do, as recently as two or three years ago, was to call customers after an outage, and say, ‘Are you back?’ They would [respond], ‘Don’t you know we’re back?”
Those phone calls aren’t necessary anymore in areas installed with the sensors. Turning the coin, the sensors afford the utility a chance to quickly tell customers they’re back on line through forums like social media and immediate news reports.
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