This is a new world to me. Do harmonics cause vibrtaions ?
were they concerned about the connections ?
Phases in separate pipe?
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This is a new world to me. Do harmonics cause vibrtaions ?
were they concerned about the connections ?
That was their excuse anyway. I am not buying into it.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
You should have asked for their study showing the detrimental effects of electron motion at the harmonic frequency(ies) in question. :grin:
Yes, they can cause vibration when conductors are not held rigidly in place. I was part of a team that replaced over a thousand feet of bus duct with MI cables, in a crawl-size tunnel, because the busses were literally humming, and rather loudly.
brian john
Senior Member
- Location
- Leesburg, VA
One of our POCO's often does installs this way. On occasion where the PVC was installed in a cabinet with knockouts there have been issues. But as noted if there is no ferrous metal between the conduits you should be ok.
ALSO depends on if they are poured and have rebar in the pour.
ALSO depends on if they are poured and have rebar in the pour.
- Location
- Illinois
- Occupation
- retired electrician
Re-bar in the pour will not be an issue unless it completely encircles one or more, but not all of the raceways.
nightmare
Member
- Location
- MD and currently overseas
current on the egc
current on the egc
I have measured 147 amps on one of the 1/0 egc's that I installed in the pipes with the isolated phases. The system that I am working on has a large number of problems that I am fixing as fast as I can with code compliance and life safety as the primary objectives. I honestly have no idea, yet, where to find the source of this current. The system is working but I am terribly afraid that I have no pathway to ground when a 1/0 egc is already carrying 147 amps. I'm looking for a shortcut to the answer because I think this is a bit of an emergency so my question is:
Is it even remotely possible for 147 amps to be induced on the 1/0 egc by the 350 amps that are being carried by the immediately adjacent 500 MCM phase conductors?
current on the egc
I have measured 147 amps on one of the 1/0 egc's that I installed in the pipes with the isolated phases. The system that I am working on has a large number of problems that I am fixing as fast as I can with code compliance and life safety as the primary objectives. I honestly have no idea, yet, where to find the source of this current. The system is working but I am terribly afraid that I have no pathway to ground when a 1/0 egc is already carrying 147 amps. I'm looking for a shortcut to the answer because I think this is a bit of an emergency so my question is:
Is it even remotely possible for 147 amps to be induced on the 1/0 egc by the 350 amps that are being carried by the immediately adjacent 500 MCM phase conductors?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I'd have to do more investigation, like checking the other EGC's, and voltage (FOP, basically) tests.
nightmare
Member
- Location
- MD and currently overseas
other egc's
other egc's
I also measured current on the other egc's. not as high but close. What is FOP and thanks for the quick response.
other egc's
I also measured current on the other egc's. not as high but close. What is FOP and thanks for the quick response.
nightmare
Member
- Location
- MD and currently overseas
voltage?
voltage?
Where/how would you measure the voltage? I'm not sure what voltage to measure. When I measured the difference in potential from phases to the ground bar I got the expected 215 V so I'm confused. That is relative voltage. Right?
voltage?
Where/how would you measure the voltage? I'm not sure what voltage to measure. When I measured the difference in potential from phases to the ground bar I got the expected 215 V so I'm confused. That is relative voltage. Right?
ohmhead
Senior Member
- Location
- ORLANDO FLA
Well heres a thought we sometimes put a clamp on amp probe around our ground rods just to see if current is on the rod or rods its common not all services but some can give you a reading of a few amps .
Meaning a flow of amps into your earth but returning to the neutral thur the earth ground . Earth made of clay/ sandy soil wet/ water table in florida plays a part .
Now heres my unprofessional opinion on this your inducing a voltage in that EG conductor it may be isolated also meaning not a good enough ground point or bad connection to ground point on both ends just like a winding in a transformer the magnetic field is strong in one pipe you have a potential to induce voltage a produce current i would think how long is the run ?
Now you said you have a spare in with each of the parallel runs why thats a metal object a wire will be inductive magnetic field crossing into that conductor for sure its a wire it will be effected ?
You may just have a secondary winding via EGC and spare conductor .But iam just thinking and theres some who have a better understanding then me .
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
FOP means fall-of-potential. In theory, you should measure almost zero volts between two points along a conductive pathway; say, from the meter terminals to the bus in a panel.
If you measure, for example, 0.07v on A, 0.09v on B, and 1.8v on C, you'd know you have a poor contact between two points somewhere along C phase, and there should be a bit of heat there.
Normally, you measure between two adjacent points, such as service wire to meter line terminal, line terminal to load terminal, load terminal to load wire, load wire to bus terminal, bus terminal to breaker load terminal, etc.
See above. It's much easier to find a small voltage drop between two points than it is to pinpoint a similar drop in voltage along a series of points.
This is an example of a voltmeter being the better tool for the job than a solenoid-type tester. Make sure you start with a high voltage setting, just in case.
ohmhead
Senior Member
- Location
- ORLANDO FLA
Well its not a isolated paralleled feeder but it kinda explains it better then me.http://www.epanorama.net/documents/groundloop/basics.html
nightmare
Member
- Location
- MD and currently overseas
investigating
investigating
I'll be spending the day and, of course, the next little while investigating and doing some very careful measuring. Any help with this one will be big so thanks in advance.
investigating
I'll be spending the day and, of course, the next little while investigating and doing some very careful measuring. Any help with this one will be big so thanks in advance.
nightmare
Member
- Location
- MD and currently overseas
i'll get back to you on the grounding questions ASAP. the system is 400 V and if you'll so me a favor and read the very beginning of the thread i think the configuration is well expoained. if not, please let me know. i have to get back to getting some measurements right away, so thanks for lookin at this. I believe the system is what's known as solidly grounded because of the attachment to the ground ring that exists at the source.
I must have missed it. 230/400 3P 4W, i guess? Was the system under heavy load when you measured the "expected 215 phase to ground"? 147 amps a lot of ground current. Are each of the phases showing the expected line current or is one significantly higher or lower than the connected load should reflect. Ground rings are common, my question is, how or where is you systems neutral/X0 connected to your earth/ground system?
Inductance ! Yes.
Inductance ! Yes.
Did this Once! 1200A feed to a tempoary motor, PVC raceways for support of parallel runs.
Found the straps on the Unistrut going up the wall getting hot and heating the PVC after 2 hours. PVC started sagging.
Removed the bolt/nuts and put in tiewraps for the duration of the change out.
Inductance ! Yes.
Did this Once! 1200A feed to a tempoary motor, PVC raceways for support of parallel runs.
Found the straps on the Unistrut going up the wall getting hot and heating the PVC after 2 hours. PVC started sagging.
Removed the bolt/nuts and put in tiewraps for the duration of the change out.
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