Neutral Voltage

[linemanfrog]

While changing out a few poles the other day, we found that there was voltage on the neutral. We have a 7.2/12.4 Grounded Wye system and voltage being present on the neutral is very uncommon. After riding the line out and not finding any neutral connections at deadends that looked bad, we backed up and started looking at equipment grounds. We found the problem in short order, a crew installed a 3phase Cap Bank and did not remove the shipping ground from the floating neutral highsides. Just a reminder to everyone that things are not always what they seem. We were about 15 spans away and were getting 90 volts on the pole ground prior to it being connected to the driven ground rod. There's no telling what the voltage would have been on the pole ground at the cap bank. After talking it over with a coworker, it is likely this cap bank had been like this for 8 or more years.

[reppy007]

While changing out a few poles the other day, we found that there was voltage on the neutral. We have a 7.2/12.4 Grounded Wye system and voltage being present on the neutral is very uncommon. After riding the line out and not finding any neutral connections at deadends that looked bad, we backed up and started looking at equipment grounds. We found the problem in short order, a crew installed a 3phase Cap Bank and did not remove the shipping ground from the floating neutral highsides. Just a reminder to everyone that things are not always what they seem. We were about 15 spans away and were getting 90 volts on the pole ground prior to it being connected to the driven ground rod. There's no telling what the voltage would have been on the pole ground at the cap bank. After talking it over with a coworker, it is likely this cap bank had been like this for 8 or more years.

Hey frog...you kind of lost me there.....floating neutral highsides.........and what is a shipping ground.....

[kooman]

What do you mean by floating highside neutral? All of our cap banks are grounded, i have seen neutral voltage before when a cap fuse was blown, you will have a voltage reading betweene neutral and pole ground.

[reppy007]

What do you mean by floating highside neutral? All of our cap banks are grounded, i have seen neutral voltage before when a cap fuse was blown, you will have a voltage reading betweene neutral and pole ground.

Glad you responded Koo....I was thinking the same thing,Its been years since Ive messed with a cap bank....but cant recall any floating highside on these in my parts.

[urban1095]

While changing out a few poles the other day, we found that there was voltage on the neutral. We have a 7.2/12.4 Grounded Wye system and voltage being present on the neutral is very uncommon. After riding the line out and not finding any neutral connections at deadends that looked bad, we backed up and started looking at equipment grounds. We found the problem in short order, a crew installed a 3phase Cap Bank and did not remove the shipping ground from the floating neutral highsides. Just a reminder to everyone that things are not always what they seem. We were about 15 spans away and were getting 90 volts on the pole ground prior to it being connected to the driven ground rod. There's no telling what the voltage would have been on the pole ground at the cap bank. After talking it over with a coworker, it is likely this cap bank had been like this for 8 or more years.

A couple of summers ago when the missouri was flooding I ran into the same thing when trying to get all the cap banks online. It had the factory series ground installed on the packs then ran to the case then the pole ground.
Whoever installed also ran another ground to the highside of the packs for the neut ct ring. The cap banks on are system are designed to open up when sensing a unusually high voltage from the neut ct. I looked it over closed it in in and took my readings. opened it back up after taking the neut reading looked it over better cut the factory ground out and all was well. That means whoever originally installed it never did their due diligence!

[linemanfrog]

On our 3 phase cap banks we "float" the primary grounds, H2's, or what ever you choose to call them, much in the same way that you "float" the highside H2 bushings on a closed delta transformer bank. From the factory, one primary bushing on each phase set of capacitors is tied together with the same bushing on the otehr two phases. When the unit leaves the factory they install a "shipping ground" which is a piece of wire that ties the "floated" highside neutral to the capacitor rack. When the cap bank was installed, the crew did not remove this "shipping ground" and the result was that the capacitor was causing voltage to be present on the main line neutral.

Hope this answers your questions.

We had this same issue a few years back where a 3 man crew got a job packet and they installed 4 or 5 cap banks in our system. A few days later, a trouble man i believe, got sent around to check a cap bank for our system control center and found the pole ground burnt badly. The crew that did the installation on all 4 or 5 banks had forgotten to remove the shipping ground on every bank they hung.

[kooman]

On our 3 phase cap banks we "float" the primary grounds, H2's, or what ever you choose to call them, much in the same way that you "float" the highside H2 bushings on a closed delta transformer bank. From the factory, one primary bushing on each phase set of capacitors is tied together with the same bushing on the otehr two phases. When the unit leaves the factory they install a "shipping ground" which is a piece of wire that ties the "floated" highside neutral to the capacitor rack. When the cap bank was installed, the crew did not remove this "shipping ground" and the result was that the capacitor was causing voltage to be present on the main line neutral.

Hope this answers your questions.

We had this same issue a few years back where a 3 man crew got a job packet and they installed 4 or 5 cap banks in our system. A few days later, a trouble man i believe, got sent around to check a cap bank for our system control center and found the pole ground burnt badly. The crew that did the installation on all 4 or 5 banks had forgotten to remove the shipping ground on every bank they hung.

I dont understand how your grounded wye system works differently than our grounded wye system, all of our cap banks are grounded on the h2 side and we do not have the problems that you describe, will the people smarter than me please help?

[reppy007]

I see what your saying now Frog,thanks.....I once mentioned that we had one where the oil switches/kyles were cycling on and off every few seconds....you could hear them in urd transformers....clicking.....not many calls on this,maybe because we got there super fast and because it was in the early afternoon.....the cap bank was just out of the sub.and I would think it effected everyone on that circuit but to this day I dont know.

[urban1095]

On our 3 phase cap banks we "float" the primary grounds, H2's, or what ever you choose to call them, much in the same way that you "float" the highside H2 bushings on a closed delta transformer bank. From the factory, one primary bushing on each phase set of capacitors is tied together with the same bushing on the otehr two phases. When the unit leaves the factory they install a "shipping ground" which is a piece of wire that ties the "floated" highside neutral to the capacitor rack. When the cap bank was installed, the crew did not remove this "shipping ground" and the result was that the capacitor was causing voltage to be present on the main line neutral.

Hope this answers your questions.

We had this same issue a few years back where a 3 man crew got a job packet and they installed 4 or 5 cap banks in our system. A few days later, a trouble man i believe, got sent around to check a cap bank for our system control center and found the pole ground burnt badly. The crew that did the installation on all 4 or 5 banks had forgotten to remove the shipping ground on every bank they hung.

Are floating for the same reason you do on a closed delta ?

[reppy007]

Speaking of closed delta banks....I knew a case where a strip center was getting strange voltage everyonce in awhile....I happened to be working nights at the time....took a look and found everything ok except the floating highside was grounded....notified another more experienced lineman the next day......Im sure they ungrounded it,but it was an old bank and must have been like that for many, many years.