Amazing to me that it could be that bad, but in this area it's the worst power i've ever seen. It can dip down as low as 80vac for short periods of time in the summer.
I've been trying to figure out what could cause this.

Slightly off topic but when I lived in Italy myself and a few other Americans lived in a rural beach community which was pretty deserted right till August First when the entire European community packed every beach villa for miles. A friend found this old analog meter which had to have a 12" scale on it 0 to 250 VAC. We calibrated the monster and dragged it out to his Villa. It was a source of amusement as we drank Peroni beer and cheap table wine. Our 220 volt service drifted from around 200 to as high as 240 Volts and this was up, down over minuets. When the entire world came to visit in August power outages were frequent and we were amazed if we got to 200 Volts. Then on September First there was a beautiful silence and only the sounds of the sea.

Al, my uncle lives in Califon towards the end of a narrow winding road which turns to dirt. A single line winds back through the wooded area with a few transformers. Every bad storm they loose power as a tree along the route will fall on that single line. Flash, bang and darkness. Outages of 3 and 4 days are normal. When Sandy rolled through it was over a week.

Ron

 

Is the line waveform always like that, or only under certain identifiable circumstances, e.g. peak usage times, wet weather etc?
Do you get the same effect using a different transformer?
Line waveform here has always been a good sinewave whenever I've checked, albeit with varying amounts of superimposed hash/spikes.

Hi,

I just started looking at it a few days or maybe a week ago. Before that, just voltage measuremnts.
In summer it can drop as low as 70v for a second, then 80v, then maybe up to 100v. it is supposed to be 120vac.
Thanks for checking.

 

Could this have anything to do with your probes or some sort of protection in between the signal and your scope? The clipped peak looks like a zener protecting the input. The rest of the wave looks like an RC sawtooth.

Like I said before, my money is on an artifact and not bad power.

Hi,

Well i checked the measuring transformer, with a pure sine i get an almost pure sine out.

 

OK MrAl showing mine. Some flat topping, maybe not as bad as yours. I used a 10 to 1 resistor attenuator to measure.
SG
View attachment 150161

Hi,

That's interesting because it shows the same gradual change to flat, but then a quick drop back to sine after the flat, just like mine, just not as bad.

I guess you used a regular CRT scope?

 

Interesting. I had no idea. Mine has always looked textbook sine whenever I’ve looked, which was rare.

Hi,

I'll check the transformer again tomorrow with the CRT scope. Thanks.

 

Greetings from the power grid of First Energy in Cleveland, Ohio. I did use a transformer simply for isolation because my late father in law did some peculiar house wiring and I have not ripped this wall out yet meaning neutral and hot may be reversed and scope ground may have gotten real ugly.

View attachment 150165

The scope is an old analog Tek 2235 with a 10:1 probe looking at a 24 VAC CT transformer (12 VAC). About 4 divisions of 10 V/Div so 40 V Pk to Pk so about 14.14 VAC RMS. MY mains coming in is generally 246 and evenly split at about 123 VAC per side. The few times I have looked at my AC mains they actually look pretty good. First Energy is like any other power company, the one people love to hate. While I can't speak for others in NE Ohio our service has been pretty reliable overall. Not great enough I am going to disconnect and sell my backup generator but pretty clean and reliable power for our needs.

Ron

Hi,

That one is not that bad really. Did you ever measure anything in the NJ location?

 

Ky not too bad

View attachment 150167

Hi,

Yeah not too bad, a little lop sided like mine but with no flat topping. Thanks.

 

Hi,

That one is not that bad really. Did you ever measure anything in the NJ location?

Hi Ya Al, I have not measured in NJ, I should have as when visiting my uncle I had my DMM with me, just never measured line voltage. I did notice the fluctuations in the incandescent deck lights.

Generally I see the entire US power grid as pretty fragile with most sub stations sitting in the open and unprotected. Those Americans living up north really dislike dark and cold and it doesn't take long in sub freezing weather before pipes start freezing and bursting. Sub stations are an easy target for problems.

Ron

 

I guess you used a regular CRT scope?

Correct, BK1405
SG

 

Hi Ya Al, I have not measured in NJ, I should have as when visiting my uncle I had my DMM with me, just never measured line voltage. I did notice the fluctuations in the incandescent deck lights.

Generally I see the entire US power grid as pretty fragile with most sub stations sitting in the open and unprotected. Those Americans living up north really dislike dark and cold and it doesn't take long in sub freezing weather before pipes start freezing and bursting. Sub stations are an easy target for problems.

Ron

Hi,

Yeah maybe the whole system is becoming overloaded. That's what it seems like in my area. They keep building houses and buildings, how can the number of dwellings increase without upgrading the infrastructure that provides the line power?

I am hoping to do some more measurements today.

 

Correct, BK1405
SG

Hi,

Ok thanks for confirming. I might do that later today too, hopefully i'll be able ot get to it just to confirm again that the measurement transformer is not affecting any measurement.
I was using a PC USB scope for now, so i wanted to use a isolation transformer (AC). I've seen it done other ways but i hate to connect a USB scope directly to the line so i have to dig out the old CRT.

 

Distortion of the power incoming has become a problem in some localities, and quite a challenge because of the resulting harmonics. I can't offer a solution, but the problem can be very real.

 

Interesting, that shows a bit of sawtooth also.

That looks an awful lot like measurements I've done on carbonator pump motors. Wonder if there was an inductive load pushing the wave shape within the house wiring (fridge, freezer, HVAC?)

 

Hello,

Yes it is a secondary, but i had proved that it is not the transformer used for the measurement it is actually the line voltage itself. Amazing to me that it could be that bad, but in this area it's the worst power i've ever seen. It can dip down as low as 80vac for short periods of time in the summer.
I've been trying to figure out what could cause this.

There are a variety of causes, rectifier/reservoirs input PSUs are probably among the worst offenders. Once the reservoir is initially charged, it just takes a blip of current on the peaks to keep it topped up. The crest factor in badly designed iron cored ballast fluorescents can also distort the waveform.

 

Distortion of the power incoming has become a problem in some localities, and quite a challenge because of the resulting harmonics. I can't offer a solution, but the problem can be very real.

Yes, any maybe it looks worse than it is here, but that tells me that they are not doing something right in this area. That along with the extreme drops in voltage in summer months.

But surprisingly they keep building new dwellings in this area. Two apartment houses for example.

 

I think there is some standard that defines how much distortion can the supply line have, maybe you should remind your power company about it.

 

If your voltages are getting that low...you or the power co. has a problem. No appliance damage? You deserve an answer from the power co.

You and your neighbors can approach the utility commission if necessary.

I don't go around checking the sine of power lines.......but have never seen ac line that bad.

Excluding inverters and generators.

 

My AC line voltage look like this



50Hz 230V RMS.

 

The red trace is line voltage near downtown Seattle. Other traces represent current through motor loads.

 

Voltage samples for below image is captured with Arduino UNO ADC with about 2 kHz sampling rate. Small voltage transformer module (bought from Ebay) was used to reduce 230 VAC to ADC. Location is Helsinki, Finland.