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Comment by amluto | Hacker News Reader

A surprising number of modern smart meters contain relays that can be used to wirelessly disconnect customers. I don’t know whether this feature is used for load shedding and/or startup, but it certainly could be.

As an aside, there are distressing reports of meter-associated fires. These seem to come in two categories: installation issues (poor contact between meter and socket) and issues with the relay itself. The former is not specific to smart meters per se, but the latter is. A device that can safely switch 100-320A at 240V is not that cheap and not that small, and I suspect that some smart meter manufacturers try to cut costs.

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Can confirm the first part - had the utility turn on a meter remotely, so they can turn it off too.

Also, around here (Portugal) you're billed for the maximum power in your contract - it starts at 3.45 kVA, I think, with 6.9 and 10.35 levels commonly available (at 230 volts, that's 15, 30 or 45 amps). Used to be that a hardware circuit breaker enforced that limit, nowadays it's the meter cutting off supply in case of excess power draw.

(No reports of fires that I've heard of.)

I don’t know whether this feature is used for load shedding and/or startup, but it certainly could be.

The last two places I lived, it was.

In the more recent one, residential customers who didn't opt in to the smart thermostat, which allows the power company to override your temperature settings in an emergency, could be automatically cut off from the grid in a crisis.

In the older one, a factory I worked for was part of a program where they volunteered to be cut off from the grid remotely in the event of a power emergency. The factory got some kind of discount or rebate for being part of the program.

At least in my area they can. I have an agreement with the power company that they can shut off my A/C for up to, IIRC, 10 minutes at a time with some maximum total time off per day to load shed in times of high load. In return I get a discount on power during the summer months.

Except for the first year where there was a bug that turned it off for an hour at a time, it's never been noticeable.

This is almost certainly not a capability of your meter as such, though the meter might be used to pass data back and forth. Either your thermostat is being controlled (i.e., via changing setpoints) or there's a device somewhere in your HVAC wiring that the utility can communicate with. What is for sure not happening is remote connect/disconnect in the meter used to shed load.

Correct! I didn't think it was worthwhile making the distinction but there's a separate interface that the power company can control that switches the A/C. I think (been a while since I paid attention to it) that it only controls the compressor: the blower is still allowed to run independently.

I worked with a power company in New Zealand that had load shedding like this (although more for water heaters IIRC). They transmitted signals on the power lines themselves at a much higher frequency than the AC delivery. The end devices also needed to support it.

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