Line Voltage Very Flat Topped, What Is Yours?

Discussion in 'Test & Measurement Forum' started by MrAl, Apr 9, 2018.

  1. Reloadron

    Distinguished Member

    Jan 15, 2015
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    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
     
  2. MrAl

    Thread Starter Distinguished Member

    Jun 17, 2014
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    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.
     
  3. MrAl

    Thread Starter Distinguished Member

    Jun 17, 2014
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    Hi,

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

    Thread Starter Distinguished Member

    Jun 17, 2014
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    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?
     
  5. MrAl

    Thread Starter Distinguished Member

    Jun 17, 2014
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    Hi,

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

    Thread Starter Distinguished Member

    Jun 17, 2014
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    Hi,

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

    Thread Starter Distinguished Member

    Jun 17, 2014
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    Hi,

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

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    Jan 15, 2015
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    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
     
  9. sghioto

    Member

    Dec 31, 2017
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    Correct, BK1405
    SG
     
  10. MrAl

    Thread Starter Distinguished Member

    Jun 17, 2014
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    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.
     
  11. MrAl

    Thread Starter Distinguished Member

    Jun 17, 2014
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    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.
     
  12. MisterBill2

    Active Member

    Jan 23, 2018
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    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.
     
  13. ebeowulf17

    Well-Known Member

    Aug 12, 2014
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    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?)
     
  14. ian field

    AAC Fanatic!

    Oct 27, 2012
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    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.
     
  15. MrAl

    Thread Starter Distinguished Member

    Jun 17, 2014
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    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.
     
  16. kubeek

    Expert

    Sep 20, 2005
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    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.
     
    -live wire- likes this.
  17. BR-549

    Distinguished Member

    Sep 22, 2013
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    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.
     
    -live wire- likes this.
  18. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    My AC line voltage look like this

    sin.png

    50Hz 230V RMS.
     
  19. ebeowulf17

    Well-Known Member

    Aug 12, 2014
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    The red trace is line voltage near downtown Seattle. Other traces represent current through motor loads.
    IMG_5124.PNG
     
  20. tsan

    Member

    Sep 6, 2014
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    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.

    voltage_230VAC_grid.png
     
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