What causes a 9th harmonic on the power line?
What causes a 9th harmonic on the power line?
(OP)
My utility is trying to help the local phone company find the source of a 9th harmonic which is causing noise on their system. The area is almost exclusively rural load with two exceptions; a lot of pipelines in the area (cathodic protection) and one large pipeline pump (1200 Hp).
We've ruled the pump out as the harmonic exists whether the pump is running or not. We've also temporarily killed out some of the cathodic protection with no lessening of the harmonic.
We've suggested a separate ground and/or 9th harmonic filters to the phone company, neither of which do they seem willing to invest in.
Any ideas for a source of that particular harmonic?
Any source for a filter suitable for a phone pedestal?
We've ruled the pump out as the harmonic exists whether the pump is running or not. We've also temporarily killed out some of the cathodic protection with no lessening of the harmonic.
We've suggested a separate ground and/or 9th harmonic filters to the phone company, neither of which do they seem willing to invest in.
Any ideas for a source of that particular harmonic?
Any source for a filter suitable for a phone pedestal?






RE: What causes a 9th harmonic on the power line?
RE: What causes a 9th harmonic on the power line?
So, my guess is that you have a rather normal harmonics profile. And then, just about anything can produce that interference, TVs, hi effificency lamps, computers, VFDs, thyristor controlled heating - anything. Just go there with a current clamp and an analyzer to trace the source.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: What causes a 9th harmonic on the power line?
RE: What causes a 9th harmonic on the power line?
We can see the problem in the substation (although, strangely enough, there is no significant 3rd harmonic). The problem worsens the closer you get to the end of the line (some 5 miles away) at one particular phone company pedestal.
We have systematically dropped various loads around the pedestal to no effect. We transfer to different substation source and the harmonic disappears, so it is specific to the sub in question and not the pedestal equipment itself.
RE: What causes a 9th harmonic on the power line?