Powerwalls Intervening without a grid outage?

[Frankman60]

Has anyone experienced their Powerwalls reporting a grid outage and taking over for 20 seconds or so for no apparent reason? This has happened five times from 5 to 6:30 PM today and is reported in the Tesla app Backup History. Each event was between 20 and 26 seconds long. I happened to have the Tesla app open one time when it happened and the Power Flow screen showed a grid outage for that short amount of time. I checked with the Utility and neighbors and they did not experience any grid outages. The Utility said that they would check our transformer but they had no record of any outages affecting our Circuit. If anyone has any ideas about why this is happening I would appreciate your thoughts.

 

[gpez]

Has anyone experienced their Powerwalls reporting a grid outage and taking over for 20 seconds or so for no apparent reason? This has happened five times from 5 to 6:30 PM today and is reported in the Tesla app Backup History. Each event was between 20 and 26 seconds long. I happened to have the Tesla app open one time when it happened and the Power Flow screen showed a grid outage for that short amount of time. I checked with the Utility and neighbors and they did not experience any grid outages. The Utility said that they would check our transformer but they had no record of any outages affecting our Circuit. If anyone has any ideas about why this is happening I would appreciate your thoughts.

This happened to me once - was at work and got an outage notification from the Tesla app. Checked my utility's status page and saw no reports of a problem. Since the app doesn't say why the Powerwall kicked in I called Tesla. Their data showed a utility undervolt for a brief moment: 226v registered and the Powerwall range is 228v-252v. Not enough to cause any problems but enough to trip the Powerwall.

Give Tesla a call and ask them for the reason. My money is on a short grid problem (voltage or frequency out of spec).

 

[Frankman60]

Thanks @gpez, that makes sense to me. That would definitely explain why my neighbors didn’t notice anything. It also explains why a few UPS backup devices in my house beeped. It’s possible that they recognized an under voltage situation before the Powerwalls took over.

I didn’t realize that I can call Tesla to find out the cause for a backup event. Tesla did not install my Powerwalls, but can I still call Tesla to get this information, and if so, what is their telephone number? Is there an event log that is accessible to the customer to look this sort of information up?

 

[ewoodrick]

There's a lot of transients that occur on power lines. In the evening, in the summer, easily could have dropped voltage or frequency just enough to trigger.
Also, if someone hits a pole, there could be some switching of the grid occurring.

The glitch could have only lasted 100ms, but once the unit takes over it waits to make sure that the grid is stable before going back

 

[NuShrike]

Could be because of the heat, your neighbor's A/Cs have lowered the utility voltage enough for the PW to kick in.

My monitoring shows voltage in my area dropped to its lowest value around 6:15PM on SCE. To 229V from the usual 245V, so it happens.

 

[Frankman60]

Thanks @ewoodrick and @NuShrike. I never thought of the Powerwalls as a voltage regulator. That’s a nice feature.

 

[gpez]

@Frankman60 I had a Tesla certified installer put my Powerwall in and have called Tesla support more times than I can count.

Powerwall Customer Support

 

[ewoodrick]

Thanks @ewoodrick and @NuShrike. I never thought of the Powerwalls as a voltage regulator. That’s a nice feature.

It's not really a voltage regulator. It's just that for many loads, you have to switch quickly. A single AC cycle can sometimes be too long. So a UPS has to catch it fast. And sometimes it guesses wrong. So yea, it can act as a voltage regulator.

That can also be a huge disadvantage. If the utility has a brown-out, some UPSs kick in and remove the load from the grid. the problem is that brown-outs can last for hours and UPSs often can't

It's a common problem for gas generators. Their frequency and voltage vary, attached UPSs can't take it and switch to battery and die. Some UPSs support wider tolerance ranges and do better. Yet other UPSs are dual conversion, so there's half that charges the batttery and half that provides AC. (Common UPSs only charge or backup.)

 

[1100MCM]

There's a lot of transients that occur on power lines. In the evening, in the summer, easily could have dropped voltage or frequency just enough to trigger.
Also, if someone hits a pole, there could be some switching of the grid occurring.

The glitch could have only lasted 100ms, but once the unit takes over it waits to make sure that the grid is stable before going back

I've actually seen this personally on my Powerwalls. Most distribution feeders (typically 12 kV transmission lines that carry the electricity to the transformer at our house or block) have reclosers installed at the beginning of the line (at the substation) or perhaps somewhere in the middle of the line. They're designed to clear momentary faults such as a tree falling on a line or a car vs. pole. They're usually coordinated with fuses on the lines to protect the feeder and to minimize outages to as little customers as possible. When an event such as a car vs. pole or a tree branch in contact with a line happens then an entire feeder will open along with the fuses serving a neighborhood block or house where the fault occurred. In a matter of seconds the recloser will close the feeder and restore most customers on the feeder while the open fuses where the fault was remain isolated and open until the fault is corrected. This process could happen up to 3 times in most cases within a span of seconds so the fault can be cleared automatically.

For most this will be seamless and won't have any major effects on electrical items in the home but I suspect this is the way Powerwall is trying to ride these momentary transients. Of course it doesn't have to be only when the feeder relays (when the recloser tries to reclose the feeder) but it can also happen with smaller transients such as frequency excursions or voltage swells or sags: Powerwall will react pretty quickly to ride that out. For most homes that don't have Powerwall it's not a big consequence anyway because most loads and especially electronics can tolerate voltage and frequency excursions pretty well.

But anyway, in a sense Powerwall is cleaning up the power supply coming into our homes which is technically more efficient. Hard to say if we'd really notice on our wallets but in theory that's how it should work.

 

[Frankman60]

Thanks to all that replied to my post. It was helpful for me to know about what is lurking on the power lines and that Powerwall is defending my home from these things

 

[Ulmo]

My PowerWalls seem to experience a grid "outage" every handful of months for which they kick into backup mode that only lasts a very short time, such as the minimum 5 minutes or so, and I can't seem to find a reason for the "outage". So far, this has been a very comfortable event for us. There is one exception: my Mac and our oven both seem to reset when this happens, the oven every time, and the Mac about a third of the time. Luckily, my main server computer seems to keep chugging, currently at uptime of 360 days, and that's only because I did an upgrade back then, not a power outage. Every other device in the house seems unaffected.