I work for a phone co an have had some trouble with power co harmonics,mainly 540hz.I can follow the offending hz with a vf anayzler with antenna, and found the resonating cap banks. I understand there are 3 ways of detuning, 1 is a HSR(7 have burned up so far), 2 is floating the netural (dangerous) and 3 is moving the cap banks.I read the tutorial understanding harmonics and I think it says tuning the HSR to bring the resonance down to the lowest. The graph shows an increase in 540hz. Usually a tele cable can reject(protect) almost 100% over 1khz, but only about 50% at 540hz. I have read some articles saying misplaced cap banks. The question I have is,is there an easy formula to detune harmonics by moving power cap banks?
moving cap banks
- Thread starter dgamble
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charlie
Senior Member
- Location
- Indianapolis
Re: moving cap banks
I highly recommend communications with the serving electric utility. They can, and probably will, move the offending capacitor bank. Get in touch with the power quality engineer and explain what you have found. Our capacitor banks are put together in a package and are not that difficult to relocate if the reason is sound.
I highly recommend communications with the serving electric utility. They can, and probably will, move the offending capacitor bank. Get in touch with the power quality engineer and explain what you have found. Our capacitor banks are put together in a package and are not that difficult to relocate if the reason is sound.
wirenut1980
Senior Member
- Location
- Plainfield, IN
Re: moving cap banks
Another solution may be changing the size of the capacitor banks, which changes the resonating frequency. If I read your post correctly, the resonating frequency right now is 540 Hz, which for 60 Hz normal operating frequency places it in the 9th harmonic. Just out of curiosity, how would moving the capacitor bank solve the problem?
Another solution may be changing the size of the capacitor banks, which changes the resonating frequency. If I read your post correctly, the resonating frequency right now is 540 Hz, which for 60 Hz normal operating frequency places it in the 9th harmonic. Just out of curiosity, how would moving the capacitor bank solve the problem?
Re: moving cap banks
Thank you,
Last question first. Please http://www.pserc.wisc.edu/ecow/get/generalinf/presentati/psercsemin1/seminars20/jewell_seminar_sep2002.pdf
see page 29 about reason to move cap bank.
I have been working with the power co to install hsr's http://www.sncmfg.com/telecom/noise_protection/hsr.html
They work but the problem is they melt and short out if the cap bank malfunctions. I have read of modeling programs http://www.transcoil.com/meetieee.pdf and wondered if anybody is using such. If I was to come to you complaining of noisy power lines, do you have a way of reducing the harmonics? My queston is which way and how far to move a cap bank? In one case they went from 600 to 1200kvar with no change in harmonic influence.
Darwin
Thank you,
Last question first. Please http://www.pserc.wisc.edu/ecow/get/generalinf/presentati/psercsemin1/seminars20/jewell_seminar_sep2002.pdf
see page 29 about reason to move cap bank.
I have been working with the power co to install hsr's http://www.sncmfg.com/telecom/noise_protection/hsr.html
They work but the problem is they melt and short out if the cap bank malfunctions. I have read of modeling programs http://www.transcoil.com/meetieee.pdf and wondered if anybody is using such. If I was to come to you complaining of noisy power lines, do you have a way of reducing the harmonics? My queston is which way and how far to move a cap bank? In one case they went from 600 to 1200kvar with no change in harmonic influence.
Darwin
Re: moving cap banks
Hello dgamble,
I'm just curious- what is a vf analyzer?
If I read your post correctly you use this device with the attached antenna to look for harmonics. My concern is that this is not how electrical system harmonics are measured or documented.
IEEE standard 519 "Recommended Practices and Requirements for Harmonic Control in Electronic Power Systems" mentions 5 testing devices:
Oscilloscope
Spectrum analyzer
Harmonic or Wave analyzer
Distortion analyzer
Digital harmonics measuring equipment
All of these items require a direct connection to the electrical system, and the O-scope generally requires skilled interpretation.
I don't dispute that the vf analyzer is reading 540 Hz, but I would recommend confirming your readings with a secondary piece of test equipment listed above before making a decision on how to best resolve this problem. Otherwise, how can you determine if the harmonics are voltage related, current related, or a combination of both?
Mark
Hello dgamble,
I'm just curious- what is a vf analyzer?
If I read your post correctly you use this device with the attached antenna to look for harmonics. My concern is that this is not how electrical system harmonics are measured or documented.
IEEE standard 519 "Recommended Practices and Requirements for Harmonic Control in Electronic Power Systems" mentions 5 testing devices:
Oscilloscope
Spectrum analyzer
Harmonic or Wave analyzer
Distortion analyzer
Digital harmonics measuring equipment
All of these items require a direct connection to the electrical system, and the O-scope generally requires skilled interpretation.
I don't dispute that the vf analyzer is reading 540 Hz, but I would recommend confirming your readings with a secondary piece of test equipment listed above before making a decision on how to best resolve this problem. Otherwise, how can you determine if the harmonics are voltage related, current related, or a combination of both?
Mark
Re: moving cap banks
Hello Mark,
I am a repairman and not an engineer so you can lose me fairly quickly. The test set I normally use is a Wilcom t132ez vf spectrum analyzer(voice frequency).It can measure directly on tele cable pairs-110ac plug in-or connected to an antenna. It measures from 45 to 4035hz.
Ten years ago when I complained the power co would send out their noise man(radio). We both attended a tele noise class and found out his equipment would not go to my trouble harmonics. I was routed to their cap bank man with little results. My tele noise engineer understood the problem and with the cooperation of the power co we installed large tuned inductors between the cap bank and the mgn.
Once I find I have a noise problem in an area I address my problems first(bonding & grounding),then I can look at power. I use the spectrum analyzer to find the "walls" of the harmonic problem in the power grid,usually cap banks resonating. Sometimes it's easy-blown fuse-2 caps on(ab phase),1 off(c phase).
Darwin
Hello Mark,
I am a repairman and not an engineer so you can lose me fairly quickly. The test set I normally use is a Wilcom t132ez vf spectrum analyzer(voice frequency).It can measure directly on tele cable pairs-110ac plug in-or connected to an antenna. It measures from 45 to 4035hz.
Ten years ago when I complained the power co would send out their noise man(radio). We both attended a tele noise class and found out his equipment would not go to my trouble harmonics. I was routed to their cap bank man with little results. My tele noise engineer understood the problem and with the cooperation of the power co we installed large tuned inductors between the cap bank and the mgn.
Once I find I have a noise problem in an area I address my problems first(bonding & grounding),then I can look at power. I use the spectrum analyzer to find the "walls" of the harmonic problem in the power grid,usually cap banks resonating. Sometimes it's easy-blown fuse-2 caps on(ab phase),1 off(c phase).
Darwin
Re: moving cap banks
Hello Darwin
Thanks for the info on the vf analyzer.
I spent part of the day researching this problem, including the links you provided, but will continue looking into it just to satisfy my curiosity.
I may be wrong, but from what I can figure out we are talking two different types of harmonics.
Although the links you provided, and what I read at the engineering library at the University today, call this problem power line harmonics, I don't think that description is technically accurate, however, I don't have anything to back that up. My thought is that if it truly was a power line harmonics problem, the POCO would be receiving all sorts of trouble calls for that particular service area. Too, they may run a risk of problems with the state utility commission for failing to provide a product that meets the state specifications.
Any chance that you are located in the Pacific Northwest? If so, I'll donate a days worth of work to take some measurements following IEEE standard 519, provided we can post the results on this site.
Thanks!
Mark
Hello Darwin
Thanks for the info on the vf analyzer.
I spent part of the day researching this problem, including the links you provided, but will continue looking into it just to satisfy my curiosity.
I may be wrong, but from what I can figure out we are talking two different types of harmonics.
Although the links you provided, and what I read at the engineering library at the University today, call this problem power line harmonics, I don't think that description is technically accurate, however, I don't have anything to back that up. My thought is that if it truly was a power line harmonics problem, the POCO would be receiving all sorts of trouble calls for that particular service area. Too, they may run a risk of problems with the state utility commission for failing to provide a product that meets the state specifications.
Any chance that you are located in the Pacific Northwest? If so, I'll donate a days worth of work to take some measurements following IEEE standard 519, provided we can post the results on this site.
Thanks!
Mark
Re: moving cap banks
Hello Mark,
I talked with my noise engineer and he has a current noise harmonics problem in Tacoma.Please e-mail me at (removed e-mail address) with your e-mail address and I will forward it to him. He agreed to talk with you. The power co here in Idaho has been terrific to work with but I don't think they would be happy to undo a fix just to recreate a problem.
I posted the power co changed a cap bank from 600 to 1200kvar and there was no change in harmonics-it was resonating with another cap bank on a different lead out of the substation. The power co engineer figured out if a third cap bank on a third lead was kept on this would lower the 540 to each. It lowered my power influence reading(noise-to-ground)from 100+dbrnc to 87db. If you consider that noise doubles every 3db, this helped a lot.
Darwin
Please use the PM system to trade e-mail addresses. Thanks, Charlie
[ February 15, 2005, 08:27 PM: Message edited by: charlie ]
Hello Mark,
I talked with my noise engineer and he has a current noise harmonics problem in Tacoma.Please e-mail me at (removed e-mail address) with your e-mail address and I will forward it to him. He agreed to talk with you. The power co here in Idaho has been terrific to work with but I don't think they would be happy to undo a fix just to recreate a problem.
I posted the power co changed a cap bank from 600 to 1200kvar and there was no change in harmonics-it was resonating with another cap bank on a different lead out of the substation. The power co engineer figured out if a third cap bank on a third lead was kept on this would lower the 540 to each. It lowered my power influence reading(noise-to-ground)from 100+dbrnc to 87db. If you consider that noise doubles every 3db, this helped a lot.
Darwin
Please use the PM system to trade e-mail addresses. Thanks, Charlie
[ February 15, 2005, 08:27 PM: Message edited by: charlie ]
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