How hot are your meters?

AEP — American Electric Power — uses GE Smart Meters for at least some of its service territory, which includes parts of Texas, Ohio, Indiana, and Oklahoma.

From Intelligent Utility
by Katherine Wolf Davis
October 29, 2015

Today’s meters are light. The old ones were heavy and dissipated heat a lot better, actually,” said Ken Dimpfl, manager of meter engineering with American Electric Power (AEP), while discussing the deep details of temperature data analytics at Utility Analytics Week in New Orleans.

AEP, which stretches across 11 states with seven operating companies, started with the analysis of AMI meter events, alarms and alerts through lab testing to understand the parameters and variables that need to be considered. They’re using advanced statistical analysis techniques to evaluate populations of meters to determine maintenance and customer needs, such as knowing just when a truck roll is needed. (And when it’s not.)

In 2008, AEP began installing AMI meters like many utilities that applied for DOE grants. Then, in 2010, they started seeing meter failures due to high temps or thermal overload.

[What agencies did AEP inform? Did AEP inform the public? Why weren’t Smart Meter installations halted pending a review?]

“This began our journey of looking at ‘hot sockets,’” Dimpfl said.  “Over the course of a two-year period, AEP analyzed roughly 25 meters that failed. Post event analysis concluded that the root cause was a poor connection at the meter.”

Dimpfl brought a meter and an adapter for a little show-and-tell of the connections during the session. Dimpfl noted that his team was happy that the meter wasn’t really the problem once they took a serious look. Instead, it was micro arcing between the meter blade and the meter socket jaw. (That’s the basic definition of a hot socket, by the way.)

When they looked at the details of what was going on, Dimpfl and his team noticed that the meter high temp alarm was factory set to 95 degrees, which meant that, unfortunately, there would be damaged equipment by the time they were notified. But now came the hard task of figuring out what temperature to reset that alarm to.

[Electric meters have the current for a building flowing through them. It is very dangerous to have damage to an electricity meter. How many Smart Meters are reaching 95 degrees or the damage threshold?]

They began to work with the meter manufacturer to look at other ways to predict issues beyond the simple alarm. Turns out that meters have internal tables that track temps.  Once AEP discovered that temp table tracker, they wanted to start reading them on a daily basis and use that information. They threw the data into an Excel spreadsheet and picked meters that were over 130 degrees (or the ones in the group with the highest temps) and, using a field order, they’d find out that nearly one out of four meters checked had a hot socket issue.

[What about the other 75% of very high temp Smart Meters?]

So they asked more questions. Dimpfl supervises a meter lab and started to play bit, running more tests. They discovered that the temp inside the meter bumped up 16 degrees with just being energized. Typical customer load, however, had a negligible impact on internal temps. They tested how sunlight works on the meter’s temp, looked at how thermocouples impact the temp accuracy, discussed the meter’s placement (in Texas or even inside a closet) and it’s impact on temps, and, eventually, developed a temperature algorithm.

“The feedback loop from the field also exposed a lot of different things and a lot of lessons learned for us,” Dimpfl added.  They moved from spreadsheets to a database to SAS for a monitoring evolution over the last four years.

The result of all this meter temp attention: These days, hot socket analysis is performed daily on roughly 700,000 AMI meters (and running), giving them tons of data to help AEP make their meters work more efficiently for both them and their customers across those 11 states of theirs.

“We had a business need. We worked with our internal folks and vendors to figure things out,” Dimpfl summarized. So if you want to know how hot your meters are, contact Dimpfl and his temp for ideas on just how to check and analyze that data to meet those business needs.

Dimpfl spoke at Utility Analytics Week 2015 in New Orleans. Utility Analytics Week is sponsored by the Utility Analytics Institute. For more information, visit

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