Voltage increase from grid, is 270 volts too much? (US split-phase 240V is normal)

For the past couple of days we've been suffering from the inverter (Sol-Ark 12K) dropping our power and I finally realized we're getting too high voltage supplied by the grid and the voltage protection kept kicking in (Max 265V). We're on split-phase 240V here in Texas so our measurements of just shy of 270V seemed really excessive. Right now I disconnected the grid and am treating this as a grid-down situation, running off solar and gennie until this gets sorted.

What kind of effects could I expect to see running the household appliances off 135V? I can't imagine that it's good.

FYI: I have 3 different multimeters with fresh batteries all measuring the same thing so I know this is accurate.

It is excessive, could blow electronics and light bulbs. Saturate transformers, maybe motors, driving excess current.

The grid has specs, and if it is being exceeded, utility should get involved to correct.

I'm not sure what would do this. Excess on 120V can be bad neutral. But 120/240V would be its own windings, don't know why it would go so high.

Maybe some automatic voltage adjustment (transformer taps) coupled with intermittent voltage loss?

I think you're best off shutting off grid feed, if you can get by, until it is fixed.

Wow, that's pretty high!
What's the grid frequency?

Either way, I'd be calling the power company.

We had a noticable water pressure drop and a boil notice happen at the same time as the increase, so I'm betting there's correlation there somehow

what kind of grid step down transformer does your power service have.

I don't know, we just have a big green box on a pad at the street, buried wire to the house

Have you called the power company yet? I really encourage you to do that. You probably aren’t the only customer affected, and quick action could save your neighbors from problems too.

My newly installed Fronius 10 kw grid tie just did a similar thing actually. I don't have the datamanager to track things exactly, but I've just been going out near the end of the day and checking the daily log. Had an output of 11.2 kw 278 Vac at one point. I have bifacial panels at a not-ideal angle for winter time production (Eastern Canada, about 25'ish degrees, we have high coastal winds here especially coming from the North). 2 strings of 13s, have been considering taking a panel out just to be on the safe side. Already allotted for our cold temps and a 20% boost from the back side of the panels, so knew i'd be in a clipping situation for sure, but under the 15 kw max at vOC. I am surprised these panels are putting out really close to their vOC, only had it going for a couple weeks now.

I didn't measure anything at the house during this time, and our grid happened to be synchronized to our local turbine for a brief period of time yesterday. Got me thinking if there was a blip in the frequency for a brief moment while that was being synchronized, it could have anything to do with it. They tend to export a bit of power onto the highline during these times, more load than our islands actually require.

I may go 12s if it happens again to be on the safe side. Wanted to maximize cloudy day generation, but not at the expense of wrecking equipment on sunny days.


In your situation, it may be a voltage regulator on the grid that's on the fritz. I'd typically see a higher voltage one one side or the other in a broken neutral situation, but strange to see it so high on the 240 side. I can't see a transformer tap putting out that high of a voltage, think they're 2.5% for every tap up or down, there's only 2 lower, a middle setting, and 2 higher taps.

I don't know if Texas has legal limits on their voltages (or legal limits on anything else either it seems) but most countries the legal limit is 10% of the nominal voltage is the maximum eg Australia is a nominal 230v country, and has an absolute maximum of 253v (Australia used to be '240v' but with a 5% limit which was 252v before we went with the worldwide standard several decades ago (except the US and a tiny handful of other countries)- mind you absolutely nothing changed except we were now '230v' instead of '240v'- the mains voltage stayed exactly the same (around 243v most of the time in the eastern states, and closer to 251v in Western Australia)
266v is 11% overvoltage for a 240v supply (and here if anything was damaged, you could claim replacement costs from the electricity supplier (so they are VERY careful to never let it happen...)- 266v is well over what would be acceptable in any country I know of...

It might be that your electrical meter is bad and need replacement. I have heard of cases where they get replaced due to issues.

UL1741 has the inverter staying online up to 110% (264v for 240v). Between 110% to 120% (288v), it has to stay connected for 12 seconds. So, once you hit 265v, the inverter can disconnect after 12 seconds.

I believe the ride through is to avoid a lot of load tripping offline, and increasing the over-voltage problem for the people left on the grid. I suppose if your inverter is exporting power, the grid should want you to disconnect early.

YAMLcase said:

I don't know, we just have a big green box on a pad at the street, buried wire to the house

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I know this is an old post, but did you ever resolve it? I am in Texas also (near Houston) and my grid voltage is typically 253 to 255V according to my DMM and the inverter as well. That is above the 5% upper limit of 252V that my utility (Centerpoint Energy) claims not to exceed. I've had them come out and they say there is nothing they can do. They did measure my neighbor's voltage at their pole transformer and said it was 252. My transformer is pad mounted on my property. The difference could be from DMM variability, although we are both using Fluke meters (don't know if theirs is calibrated; mine was at one time, but is way out of date).

Is this something I should make a stink about or just live with? Once Growatt increased the max voltage limit on the inverter, it hasn't faulted, but I don't want it, or other electronics to wear out prematurely. We have been in this house for almost 3 years and haven't seen LED bulbs burn out prematurely (so far).

ohsolar said:

It might be that your electrical meter is bad and need replacement. I have heard of cases where they get replaced due to issues.

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Electrical meters can indeed cause problems - but there's no way for them to cause an overvoltage.

lapsmith said:

I know this is an old post, but did you ever resolve it? I am in Texas also (near Houston) and my grid voltage is typically 253 to 255V according to my DMM and the inverter as well. That is above the 5% upper limit of 252V that my utility (Centerpoint Energy) claims not to exceed. I've had them come out and they say there is nothing they can do. They did measure my neighbor's voltage at their pole transformer and said it was 252. My transformer is pad mounted on my property. The difference could be from DMM variability, although we are both using Fluke meters (don't know if theirs is calibrated; mine was at one time, but is way out of date).

Is this something I should make a stink about or just live with? Once Growatt increased the max voltage limit on the inverter, it hasn't faulted, but I don't want it, or other electronics to wear out prematurely. We have been in this house for almost 3 years and haven't seen LED bulbs burn out prematurely (so far).

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252v is 105% of 240v. That should be well within the design range of devices.

DIYrich said:

252v is 105% of 240v. That should be well within the design range of devices.

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If it were at 252 or less, I would accept it. But since it is always a few volts above 252, that is the question.