Want IoT? Here's How a Major US Utility Collects Power Data from Over 5.5 Million Meters
Monday, September 7, 2015 at 8:56AM
Todd Hoff in Example, IoT

I serendipitously found this fascinating reply by Richard Farley, your friendly neighborhood meter reader, in a local email list giving a rare first-hand account of how the Advanced Metering Infrastructure works in California. This is real Internet of Things territory. So if it doesn't have a typical post structure that is why. He generously allowed it to be reposted with a few redactions. When you see “A Major US Utility”, please replace it with the most likely California power company.

Old mechanical meters had bearings that over time wore out and caused friction that threw off readings. That friction would cause the analog gauge to spin slower than it should, resulting in lower readings than actual usage -- hence "free power". It's like a clock falling behind over time as the gears wear down.

For A Major US Utility "estimated billing" happens when your meter, for whatever reason, was not able to be read. The algorithms approved by the CPUC and are almost always favorable to the consumer. A Major US Utility hates to have to do estimated billing because they almost always have to underestimate based on the algorithms and CPUC rules. Not 100% sure about this, but if they underestimate, they have to eat the cost. In the rare case they overestimate (i.e., you were on vacation during the missed period), you will get "trued up" in the next billing cycle.

A Major US Utility does not see your actual use in "real time". For those interested in the nuts and bolts, here's how A Major US Utility’s AMI system works (AMI is short for Advanced Metering Infrastructure):

Your meter also has a capacitor which gives it time to send out a "last gasp" message if you lose utility power. A Major US Utility (usually) knows when you lose power. Generally these last gasp messages get through >80% of the time, but it varies by area density and topology.  Success rate partly depends on how many neighboring meters the message has to get relayed through. When your power goes out, it usually also does for most of your neighbors, so the relay chain might get cut off. Success is better at the edges of outages where neighboring meters still have power.

Many utilities measure residential power usage every 15 minutes and some pilot projects are working with measurements up to every 15 seconds, enabling something called "load dis-aggregation" analysis, which is the ability to identify usage of individual appliances based on their power signatures, and even identify when you have an appliance problem such as your refrigerator compressor going out. As you might imagine, this generates A LOT of data, as well as some serious privacy concerns! 

 

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