Hello there,

In the picture attached you can see the line voltage is very flat topped. Much more than i would have expected.

What is your line voltage waveshape looking like? Is it also flat topped that badly?

 

Where's the voltage scale? Power line line or standby generator line?

 

The bits in between the flat tops aren't very sine shaped either.

 

Are you sure it is not a measuring error?

 

If you're taking that reading from the secondary of a transformer, it looks as though the transformer core could be saturating on the peaks.

 

You’re looking at some sort of artifact. Power from the utility company will be indistinguishable from a sine wave to a very high degree of precision.

 

If you're taking that reading from the secondary of a transformer, it looks as though the transformer core could be saturating on the peaks.

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.

 

You’re looking at some sort of artifact. Power from the utility company will be indistinguishable from a sine wave to a very high degree of precision.

Hi,

That's what i thought, so i asked to see other peoples line voltages if possible.

 

Are you sure it is not a measuring error?

Hi,

Yes i checked. I can decrease input voltage to the measuring transformer and see no difference, yet when i do this same experiment with a sine wave generator i see a difference when i decrease voltage.
For some unknown reason this 'side' of the line is very bad and i dont know why yet.
I was hoping to see some other people's line voltage waves too.

 

The bits in between the flat tops aren't very sine shaped either.

Hi,

Yes, that's strange too. Cant explain it.

 

Where's the voltage scale? Power line line or standby generator line?

Hi,

Power line. It's a 120vac line, but the peaks there are lower due to the flat topping effect.

The 3rd harmonic is around 5 percent, the 5th around 4 percent.

 

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.

 

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.

 

Power from the utility company will be indistinguishable from a sine wave to a very high degree of precision.

Not once all your neighbors power all their electronic devices that only draw current at the peak of the line voltage.

It has been a long time since I looked at line voltage but I remember that it was _not_ a pretty sine wave. There was distortion at the peaks. Not "pretty" distortion like in MrAl's picture, though.

 

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

 

It has been a long time since I looked at line voltage but I remember that it was _not_ a pretty sine wave. There was distortion at the peaks.

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

 

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.



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

 

Ky not too bad

 

Ky not too bad

View attachment 150167

Interesting, that shows a bit of sawtooth also.

 

Nope it's not as good as Ron's LOl
I tested away from my supplies on a outlet across the room it's just about as good as Ron's