Generator CT's

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frofro19

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VA.
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Master Electrician
Ran into a odd situation (or odd to me). Wired up a 100 KW generator for a dairy farm that was feeding a 400 amp ATS. It was a older generator and had one CT on one of the ungrounded wires.
We had some wire left over that was 350 kcmil and used that which is rated for 250 amps so we parralled 2 sets good for 500 amps. When we had the one CT on phase A, the generator was working properly. After we installed the second set of conductors, we put the CT on the B phase instead because it just fit better around the wire. Wasn't a lot of room in that area. Then the generator would not generate any power. The generator would run but not generate any power. Switched A phase with B phase on second set of wires which were directly across from the first set and still didn't generate any power ( not that I thought that would fix the issue). Once we put the CT back on A phase on the original set of wires, everything worked properly. Any idea why this happened and how close in length should the parallel conductors should be? The one set is about 10 inches longer than the others at the generator to be able to fit into the provided lugs.
 
What is the CT for?
And was it possible that the CT needed to be rotated so that it’s waveform was in sync with the power waveform.
 
frofro19 said:
Ran into a odd situation (or odd to me). Wired up a 100 KW generator for a dairy farm that was feeding a 400 amp ATS. It was a older generator and had one CT on one of the ungrounded wires.
We had some wire left over that was 350 kcmil and used that which is rated for 250 amps so we parralled 2 sets good for 500 amps. When we had the one CT on phase A, the generator was working properly. After we installed the second set of conductors, we put the CT on the B phase instead because it just fit better around the wire. Wasn't a lot of room in that area. Then the generator would not generate any power. The generator would run but not generate any power. Switched A phase with B phase on second set of wires which were directly across from the first set and still didn't generate any power ( not that I thought that would fix the issue). Once we put the CT back on A phase on the original set of wires, everything worked properly. Any idea why this happened and how close in length should the parallel conductors should be? The one set is about 10 inches longer than the others at the generator to be able to fit into the provided lugs.
Click to expand...
What is the total length of the run? If one run is 4'2" and the other 5', the current split will be 54.5% on the short conductor and 45.5% on the longer conductor. That could be enough to overload the shorter conductor. If the runs are 9'2 and 10', there would be about 5% difference in the current split.
 
don_resqcapt19 said:
What is the total length of the run? If one run is 4'2" and the other 5', the current split will be 54.5% on the short conductor and 45.5% on the longer conductor. That could be enough to overload the shorter conductor. If the runs are 9'2 and 10', there would be about 5% difference in the current split.
Click to expand...
I believe the runs were around 25 feet in length.
 
mopowr steve said:
What is the CT for?
And was it possible that the CT needed to be rotated so that it’s waveform was in sync with the power waveform.
Click to expand...
Not sure what the CT was for except for monitoring the amp draw on the generator. Unfortunately there was no paperwork and the generator was a 1999 model that came from a chicken farm out west. Tried to find some information on it but haven't found anything yet. The CT needing to be rotated could have been the issue. It had 2 CT's but the one was not used previously so we didn't install that one. Generator is producing power when needed so hopefully all is good.
 
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