Distortion on the Power Line

Please ignore my troll. I have triggered him and he posts nonsense after many of my posts.


The static load of your PS audio unit is pretty small when it is not supplying power to anything else. That static load will not impact the THD. 


I am sorry that people like that have to ruin it for others. Feel free to PM me. 

Is that a consistent 7%, or high during the day and drops at night?  If it's drops at night it is likely Air Con, but even then that is a fair amount of THD. As it is incoming I assume the PS unit is measuring voltage THD.


It's pretty easy to determine if the issue is any part of the circuit from your PS unit all the way back to the transformer. Turn off all the breakers in your house except the one to your PS unit(s), and turn off the equipment connected to the PS. If the distortion is still high, then it's a local line issue not your feed. You could alternately just turn off all the loads in your house but the breakers are probably fastest. Without any loads, any corrosion, etc. will not impact THD.

The best thing would be to determine if it is your own home our outside ... hence the 0 cost, quick method of figuring it out I described above. If you determine its outside your house you may have a remedy with the power company so yes it is actionable.

Typically a solar power system would have very low voltage THD unloaded, but the potential for higher current THD loaded. They are measured and rated for current THD.  The output impedance should be a lot lower than the output impedance of a shared transformers unless the system is rather large. To that end, the grid should be dominant but no guarantees. It is certainly something to consider.

jea48,

If you don't have one, you can pick up used Fluke 43/43B for < $1,000 used on EBAY which is fine for single-phase use. The Fluke 41B is an older unit, but ones in good condition go for <$500 regularly with required accessories. There is even one with a 1 year warranty for $550. They come standard with 1000:1 current probes with BNC connectors. I have hooked up a 10:1 current probe and used one for low power measurement as well.


The 3 phase units are pricey even used.

I was not suggesting for the casual user, more for electricians who want to step up their diagnostic capabilities (if they don't have this already), or helpful EEs. If you need a certification training to interpret the basics of what comes out of those meters, then I probably don't want you touching anything I own.


The "certified" Power Quality Testing designation I have heard of is by the Association of Energy Engineers.  Is that what you mean? You don't have to be terribly qualified to enter their program so it feels like another 3 letter designation so popular on LinkedIn profiles and business cards, but conferring questionable abilities on those holding it. Education is great, but as pointed out in another thread 60% and 90% are often both passing grades.

Believe it or not, power companies may be interested if you get the right person. High THD is not to their benefit or liking.