Checking parallel conductors from a pad mount transformer

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DChizz

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I am in the process on installing a 3 phase 208 volt 3200 amp service for a shopping center. Currently I have installed 8 sets of 750 kcmil alluminum underground from a pad mount transformer. 5 sets to a 2000 amp main disconnect and 3 sets for a 1200 amp main disconnect.
i have terminated all the conductors at the transformer and both main disconnects. These were all black conductors that were color coded with tape and although I am very confident that all of the color coding was done correctly, I would like to double check the color coding just to be sure that everything is correct before the utility company installs their primaries. My question is, what is the best method to test for continuity between phases and from each phase to neutral at the disconnects? Obviously a standard tester will read continuity due to the windings from the transformer so what do you recommend? Thank you
 
Take them off the transformer.

Tone tester? Put one lead to one of the conductors and the other to the neutral. I'm assuming your neutral is at least one size smaller than your ungroundeds for easier identification. If not you may have to find something else to land the lead on. I've found that the signal is much stronger if the resistance is similar on both leads instead of one being connected and the other dangling.
 
You're just wanting to make sure you didn't mislabel an end to one of the conductors correct?

Why couldn't you just disconnect from the transformer, keep all conductors of each phase tied together at that end, go to the other end and use a dmm to check for continuity between the conductors?
 
It may be worth just trying a DMM and see what you get. You may be able to discern the difference. In my experience, when I measure through windings, I dont get as "solid" a value as I do with a regular conductor. Through a winding, the value seems to change over time.
 
electrofelon said:
It may be worth just trying a DMM and see what you get. You may be able to discern the difference. In my experience, when I measure through windings, I dont get as "solid" a value as I do with a regular conductor. Through a winding, the value seems to change over time.
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It might be worth the experience to try, but I would not rely on this method at all. Call it education. Not many of us have meters bouncing around in our trucks to measure that level of winding resistance
 
ptonsparky said:
It might be worth the experience to try, but I would not rely on this method at all. Call it education. Not many of us have meters bouncing around in our trucks to measure that level of winding resistance
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Usually it is pretty obvious, at least when I have done it. I assume it is due to capacitve effects. With the conductor, the resistance value will be stable, and the thru the winding value jumps all over.
 
FWIW, if you only want to verify no cross wiring, you can leave one xfmr terminal pad of conductors connected.
 
Thanks for the feedback. Pulling off 32 750's and re torquing them didnt sound fun so I figured I would stir the pot. Although a dmm is probably fine, I think I'm going to go into my tool cage and dig out the Simpson meter. I agree that the windings in the transformer (with the proper meter) will not read infinity and it should be fairly simple to double check the conductors without having to pull them off of the secondary bus. Thank you all
 
Colored wire for parallel runs is your friend. I know it's been around for a while but we are starting to use a lot more of it. Working on a 2000 amp service right now with generator backup was much easier without the phase taping we usually have to do.
 
Cow said:
Colored wire for parallel runs is your friend. I know it's been around for a while but we are starting to use a lot more of it. Working on a 2000 amp service right now with generator backup was much easier without the phase taping we usually have to do.
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Yes, takes all of the guess work out of it and looks more professional. Around here, there is no additional cost for the large sizes in colors, but there may be additional lead time.

I recently wrote the specs for a number of cable bus installations, and specified the use of phase colored insulation. The electricians loved it, and there is no question about landing the conductors correctly, unless you are color blind.
 
An 'LCR' meter should be able to see the inductance of the transformer secondary. Something such as:
http://www.bkprecision.com/products...dual-display-handheld-lcr-meter-with-esr.html

Basically you are measuring the _AC_ impedance of the circuit, rather than the DC impedance. The above meter applies an AC test voltage and measures the current flow. The transformer secondaries will impede the AC current flow far more than at DC.

Given the labor involved in disconnecting and re-terminating, $300 for a meter that will do the job might not be so horrible. Yes, you could 'homebrew' a test using a suitable AC power supply and a clamp meter...but this might not look very professional.

-Jon
 
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