Overhead 13.8kV lines into CLX and then cable Tray

[mrrjw]

We have to take down a section of 13.8kV 4/0 overhead lines and connect it to CLX to run it in an existing cable tray. The plan is to connect each side at the poles with CLX and then run down into a cable tray. The question is what to do about the ground. The overhead line has a lighting shield on top. But I would assume that we do not want to bring that into the cable tray. So, what do you ground the CLX at the ends to? Do we connect the three phases to the overhead lines and then continue to run the ground from the CLX back to the tray and ground it there?

Any help would be appreciated. Thanks.

 

[bob]

We have to take down a section of 13.8kV 4/0 overhead lines and connect it to CLX to run it in an existing cable tray. The plan is to connect each side at the poles with CLX and then run down into a cable tray. The question is what to do about the ground. The overhead line has a lighting shield on top. But I would assume that we do not want to bring that into the cable tray. So, what do you ground the CLX at the ends to? Do we connect the three phases to the overhead lines and then continue to run the ground from the CLX back to the tray and ground it there?

Any help would be appreciated. Thanks.

Does the OH ckt have a neutral? When you say

"The plan is to connect each side at the poles with CLX and then run down into a cable tray"

does that mean you are taking the OH ckt down into the tray with cable and back up OH on the other side?

 

[weressl]

We have to take down a section of 13.8kV 4/0 overhead lines and connect it to CLX to run it in an existing cable tray. The plan is to connect each side at the poles with CLX and then run down into a cable tray. The question is what to do about the ground. The overhead line has a lighting shield on top. But I would assume that we do not want to bring that into the cable tray. So, what do you ground the CLX at the ends to? Do we connect the three phases to the overhead lines and then continue to run the ground from the CLX back to the tray and ground it there?

Any help would be appreciated. Thanks.

The overhead static wire should be run to a ground every time where there is a tap. That downcomer is what you should bond your ground wires to that is emerging from the CLX termination. Do you have a pole disconnect/fuse? You should connect lightning arrestors on the load side. You should add lighting arrestors even if you don't have a disconnect. Then of course connect the other end of the ground in the receiving "Service Entrance" switchegar.

 

[stickelec]

The overhead static wire should be run to a ground every time where there is a tap. That downcomer is what you should bond your ground wires to that is emerging from the CLX termination. Do you have a pole disconnect/fuse? You should connect lightning arrestors on the load side. You should add lighting arrestors even if you don't have a disconnect. Then of course connect the other end of the ground in the receiving "Service Entrance" switchegar.

Does the NEC require grounding to the Static-Line?

 

[mrrjw]

"""Does the OH ckt have a neutral? When you say"""
I am not sure. I am going to walk it down today to see. One engineer over there is saying that the lightening shield wire is a neutral to a 13.8kV transformer. I have never heard of a lightening shield wire being used as a neutral on a 13.8kV oh line. But I will find out today.


"""does that mean you are taking the OH ckt down into the tray with cable and back up OH on the other side?"""

Yes sir.

 

[mrrjw]

We went out and walked it down. It looks like the shield wire is grounded at each pole, as expected. However, the shield wire is not connected to any 13.8kV transformer at the end. It is simply grounded. It does not connect to any neutral of a transformer.

Therefore, I would sugeest that the line entering the tray should not be connected to the shield wire as you wouldnt want to introduce a path for lightening into the cable tray if you do not have to. We are going to ground the CLX to a new ground well on each side. We will then connect the shield wire, on a separate conductor to the ground well and then run a 2/0 underground to connect each ground well. That will meet the clients request to keep the shield wire connected and ground the CLX without a direct path for lightening to travel.

Any comments? THANKS!

 

[bob]

As a minimum I suggest you install lightning arresters on both riser poles and on the pole one span back.

 

[boboelectric]

Who's engineerining this shot? I wouldn't call this one.

 

[stickelec]

As you observed, the Static Line is there for Lightning protection...only. I won't say it is the thing to do, but I have seen them tied to the site ground-grid.

I do agree 100% with Bob. In troublesome areas I have added an additional set of MOV's one span back and seen a marked reduction in losses related to Lightning... Although the addition of a quality TVSS system probably helped a lot as well.