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THD Measurements From Electric Company!

Discussion in 'Audio Hardware' started by Soundgarden, Jan 13, 2021.

  1. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Gas heat yes. Also have a gas fireplace. It's switched on and off with good ol' fashioned electricity but it's not on at night, nor does it cycle.
     
  2. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Yes, I think this is right. Can't think of anything else of consequence.

    As for the higher and more meandering THD on Ch2... you said you thought maybe "computer, etc." I just have laptops though, no big computer or server set up or anything like that. Hard for me to have a sense of what that would correspond to. But it's present every day for at least a while.
     
  3. Uglyversal

    Uglyversal Forum Resident

    Location:
    Sydney
    I wouldn't have thought that would be of importance but frost free fridges on top of the regular motor/compressor function they have a mechanical timer that activates the defrosting cycle, which is basically a heater inside the freezer, perhaps that heater is showing?
     
  4. Ingenieur

    Ingenieur Forum Resident

    Something is turned on when you wake up and turned off when you go to bed.
    A small computer might do it, switching power supply. It's always on the same leg. TV, cable box, etc.

    the smaller the load in relation to the system's capacity, the higher the THD.
     
  5. Ingenieur

    Ingenieur Forum Resident

    Electric heaters are typically resistance type. They are linear and would not cause THD like a motor or switching power supply.
     
  6. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Ahh... I think I've got it. I get up, go downstairs, open up the laptop. Some days I use it more than others. Some days I have my phone plugged in and charging through it. Some days I have teleconference meetings which REALLY heats the damn thing up but which also varies quite a bit. I think this fits that pattern on Channel 2.
     
  7. Oelewapper

    Oelewapper Plays vinyl instead of installing it on the floor.

    Smart TV doing automatic updates or a recorder starting to record a late night broadcast.
    A lot of reasons for smaller loads to kick in.
     
  8. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    No recorder. But yes, a smart tv. Do they do regular updates when they're powered off? Can't imagine they're doing multiple updates a day.
     
  9. bdfin

    bdfin Forum Resident

    Location:
    Washington State
    I'm no expert....... but logic tells you that a dedicated line from the main breaker box has the cleanest unaffected power from your main line w/o being on a circuit with other lights, heaters, mini fridges or whatever else in on the same line causing other noise in the circuit. My listening room is detached from house but has it's own power box that comes 15 ft with from main power pole. However that box was older and had screw in fuses not breakers ,ran some lights, electric heater and stereo gear........and ALSO a 200 volt well pump. Needless to say I replaced that box with new, installed new breakers fixed bad ground etc. Still run all the above and more but on proper separate circuits and IT MADE A HUGE DIFFERENCE. I also am not a huge proponent of FANCY power cords but in many cases, cables upgraded from stock especially for AMP or RECEIVER also made SOME difference. Not fancy 500.00 or more cables, just a 100.00 larger gauge one on sale for 75.00. No one is forced to buy the best but there is a difference between BETTER and Fancy.
    But to each his own............
     
    Swann36 and Soundgarden like this.
  10. Oelewapper

    Oelewapper Plays vinyl instead of installing it on the floor.

    Fair point those don’t take long, it could also be the opposite, outdated so it became part of a botnet.
     
  11. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    A fridge cycling on/off will show up in THD on its own channel. Will it also show up on the other channel?
     
  12. Oelewapper

    Oelewapper Plays vinyl instead of installing it on the floor.

    No
     
    Soundgarden likes this.
  13. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Look at this one. Why is there an alternating pattern, where first there's a cycle on Ch 2, then Ch1. It's like the same signal out of phase. But that would make no sense...

    And this is happening well before I woke up that day.

    [​IMG]
     
  14. Oelewapper

    Oelewapper Plays vinyl instead of installing it on the floor.

    Over there in America the two phases are sometimes combined into 240 volts for high power devices, right?
    Maybe it’s related to that?
     
  15. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    The harmonic distortion (which is odd-order-only on AC sine power, so 60Hz -> 180Hz 3rd harmonic) just causes higher frequency ripples in the AC.

    [​IMG]

    The reason why it is to be avoided in power systems (from the utility's standpoint) is that you'd end up with more current flowing over the neutral connector and less power delivery efficiency. In your two-phase home system, when both sides of the breaker box have equal draw and power factor, 40 amps could mean 0 amps flowing over the neutral wire back to the pole. Since grounding and grounded conductor are usually tied together, neutral current can also mean an AC voltage appears on chassis ground when this current must otherwise be carried away by the conductance of neutral and the ground stakes.

    It seems they didn't use a third channel to measure the distortion of 240V between the two phases.


    In the power conversion of audio devices, you usually have
    - a transformer (which converts to a lower AC voltage),
    - rectifier (which turns the minus part of the waveform (the curve below zero shown above) into positive and doubles the apparent frequency of voltage pulses,
    -and capacitors, which charge up from the incoming current, and supply power when the AC waveform goes to zero 120 times a second.

    It is quite easy to realize clean DC with distorted AC. Higher frequencies are filtered by induction in transformers and chokes, and the higher frequency harmonics still generate power, just less efficiently. (Consider that switch-mode power supplies turn the incoming AC power on-and-off 50000 times a second, and still provide DC regulated power which can have ripple in the nanovolts.)

    These are the devices that cause the distortion, though. A resistive space heater or incandescent light doesn't demand current differently than the sine wave of AC. Electronic devices without power factor correction, instead, demand more current from the system when the voltage of the power waveform is dropping, or only draw power when the AC voltage is above the threshold to charge a capacitor some more.


    In any case, are you going to pay for having your own pole transformer installed? Is the high-tension wire feeding pole transformers clean?
    THD appears not affected by your load, but by the power factor of neighbor's clothes washer, furnace blower, and the motors of the factory down the road that are also using devices that don't have a 1.0 power factor (like your audio amplifier).


    The scale here is THD transients that last for about 20 minutes. Something like a furnace scheduled to go on in the morning, and otherwise you don't draw enough current to register any THD, but whole-house heating would normally draw from both phases. Could be showing you how long it takes to bake loaves of bread at the factory downtown.
     
    Last edited: Jan 14, 2021
    Shawn, Soundgarden and bdfin like this.
  16. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Yes, that's right. I have double-pole breakers for: dishwasher and disposal; kitchen and microwave (almost certainly fridge is here); AC; and dryer.
     
  17. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Thanks for this explanation. I'm just trying to understand what I'm seeing a little better. Obviously there are some things I can address and some things I can't.

    Like a power-hungry MacBook Pro, with iPhone charging through it while stuck on a zoom call... if that explains the THD on Channel 2 then that's not something I'm going to be doing when listening to hifi audio.

    But if even I were going to do that, is the THD I'm getting going to impact sound quality? Or is all this well below audible levels? Because after all, that's really what I'm after here.
     
  18. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    Yeah, so why an alternating current draw here? First Ch1 for a set amount of time followed by Ch2 for the same amount of time, press repeat.
     
  19. Oelewapper

    Oelewapper Plays vinyl instead of installing it on the floor.

    Wow I didn’t know that so many American devices run on 240v!
    Every consumer product runs on 230v here, only heavy industrial equipment runs on the high power 400V
     
  20. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Different computers decided to wake up and install Windows 10 updates? Who knows.
     
  21. Soundgarden

    Soundgarden Forum Resident Thread Starter

    Location:
    Bend, Oregon
    As much as I love staring at data, there's only so much of this I'm going to be able to understand. And even if I did understand it, there's only so much that I'd be able to do to reduce distortion. And I don't even know if the distortion is going to have any impact on my sound quality...

    Really the question is whether this information is of any value in determining whether to invest or even experiment in power conditioning. Honestly, I'd rather not. And soon I'll have whole house surge protection. So if I don't need surge protection or power conditioning at the outlet... maybe I will just get more outlets installed and do any with a power strip/power/conditioner/surge protector entirely.
     
  22. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    No buzz, no problem.

    Here's a clip I made of less to more harmonic distortion, although this was really for pointing out that ground loops can take on any type of sound depending on the path.

    60hz-distortion.flac
     
  23. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    The double-pole breakers for dishwasher and disposal are likely because they ran a single 12/3 wire for both those appliances and double-throw are required by code; those appliances and your microwave and refrigerator run on 120V.

    I overlooked an obvious source of the cycling morning pulses on different phases: the refrigerator, wine cooler, garage kegerator, or deep freeze. See if they run for 15 minutes at a time every hour when you're not peeking in the door (a digital audio recorder and waveform viewer will answer this easily). A water heater also cycles on and off, but silently.
     
    Shawn likes this.
  24. rpd

    rpd Senior Member

    Location:
    Nashville
    How would you describe huge difference? What are you actually hearing?
     
  25. alarickc

    alarickc Vinylholic

    Location:
    Shaker Heights, OH
    It's not audible because you're audio gear isn't using line-AC anywhere near the audio circuit. Your gear uses line power solely to produce the DC needed to operate the amplifiers and logic components of your equipment. If your power supplies are competently designed at all, they'll laugh off THD that meets IEEE standard. If not, get new power supplies.
     

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