If I see harmonics on my meter, breaker, etc. should I be concerned?

A question that we often get is: I looked on my meter and I see harmonics, is that a problem? The question is at what level of harmonic current or voltage do I become concerned? 

These days, with a lot of the meters that we put on power systems, we can measure voltage distortion, current distortion, harmonic current, right through a breaker or any other device in our power system. And, at what level do I become concerned? The real thing is that harmonics are the new normal. We're going to have a lot of harmonic current flowing through the system because of LED lights, variable frequency drives (VFDs), and a lot of other non-linear loads or other loads that create harmonics. Where I should be concerned is when those levels exceed a certain value. The value is not necessarily in percentage, we've talked to some of these FAQs about percentage distortion versus actual amps. The actual amps of distortion and the actual voltage distortion is really what we want to be concerned with. 

So I've said in some of the other videos, 20% current distortion, or 20% of my transformer is loaded with harmonic loads. Meaning I have a thousand KBA transformer, 200 horsepower worth of loads. I should probably start thinking about whether or not harmonics are going to be a problem, but again, being the new normal, we do expect that. And just because you haven't seen them on a meter doesn't mean it's unusual by any means. Now, the other thing is we always say is that harmonics are not a problem, unless they're a problem. So, you have to expect that if you don't have actual problems, meaning overheating, MIS operation, and other things, then you might not have a problem. Let me just show you real quick a couple key points to consider. If I have a transformer and I put one harmonic load on my transformer, let's say it's a VFD. I switch over from across the line to a VFD on a 30 horsepower VFD. And I have a thousand KBA transformer during startup, that's the only load on this power system. So my current is going to look like this. 

In terms of total harmonic distortion, as a percentage is going to be maybe 40%. This is a small load on a big system. I'm not concerned with that. Again, if I'm not a 20% load or more on this transformer with harmonic load, I'm not really concerned. The other part of it is this very little bit of current coming out of here is going to produce a very little bit of voltage distortion on the boss or on the system. The other thing that comes into play is what if I add in cross line motors and I add in 500 horsepower worth of load on there? All of a sudden this THD through my system now goes way down and I'm less than 10% or 3% in terms of current distortion. My voltage THD is the same whether I have this load here or not. Because voltage distortion is based on the current flow through the impedance. 

I really want to take a look at what that current looks like in terms of magnitude, in terms of amps and my voltage distortion in terms of THD because my voltage doesn't vary that much between a four 80 volt system or a 2 0 8 volt system. Those are the kind of things that we consider. And, just because you see some crazy wave form on your meter, doesn't mean you have a problem. If you have capacitors on your power system, that's a whole other consideration to think about. You could have harmonic resonance, which we've talked about in some of these FAQs. So those are the other kind of things to consider, but just because you see current, that looks funny on your system, doesn't mean you have a problem with harmonics.