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Utilities also are finding these new Internet protocol (IP)-based networks can do more than just enable the smart grid.
No Need for Speed
By 2011, when PPL decided to expand its DA system to the Poconos, an area of wooded hills and valleys in northeastern Pennsylvania, it had decided against WiMAX for two reasons: first, the area's topography worked against the technology, which pretty much requires a line of sight between the towers and the DA devices; second, the existing WiMAX system had been unreliable. Equipment issues and radio interference had caused major headaches. Figura said they could have solved the first problem “with a lot of repeaters,” which would have raised costs substantially, but, more critically, experience with the existing WiMAX system had “left a bad taste in our mouth.”
Further, he added, the utility began to realize it did not need high-bandwidth communications in the Poconos. “Unless we want video on the side of the pole, I'm personally not convinced we need megabytes of data per second going out to a DA device,” he said, adding that “it takes maybe 200 bytes of data, not even kilobytes, to send the status of a recloser or capacitor — not a lot of data.”
In addition, new communications protocols such as DNP 3.0, which is commonly used in SCADA systems, “records all your events. Why don't I just wait for the device to tell me there's a problem instead of always checking in on it? We don't need to pay for huge bandwidth,” Figura said.
After a year of study — and a change in perspective — PPL has decided on a new communications strategy for DA: commercial cell phones. “We're using the same tower, but it's completely isolated from rest of the traffic. It's a pure Ethernet-based system with a private IP address,” Figura said. “We're seeing about 3 MB/sec of capability, which is about what we're getting from WiMAX.” Latency, he added, is about 200 msec.
Additionally, said Figura, with 80% to 90% of PPL's outages occurring during non-storm events, PPL questioned whether its customers would be willing to spend millions of additional dollars for a private radio system to survive a hurricane. On a final note, Figura said, “Our core business is power, not communications. For AT&T, Verizon and Sprint, that's their business. We have 10,000 sq miles to cover, so it didn't make sense to spend the money to build a system that would survive a hurricane.”