×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

utility PT/CT secondary circuit

utility PT/CT secondary circuit

utility PT/CT secondary circuit

(OP)
Hi all,

we need to connect utility's PT/CT secondary circuit to the meters (100 m away), we would like to use the same duct bank (concrete encased) we use for power cables (25kV),

Is this possible to do?

I'm worried about power cables interfering with the secondary signal from the PT/CT. I didn't ask utility measurement guys yet , just wanted to have your opinions/experiences first.

Thanks

RE: utility PT/CT secondary circuit

I have never see this done. I'm on the rod and I don't have my codes with me but I don't think that most codes will allow this. I expect that the utility will have standards that you must follow. Ask the utility rather than us. If you want an answer from the codes, where are you?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: utility PT/CT secondary circuit

Dedicated conduit only.  The only one that can really answer that question is your utility meter department.  If they don't like the installation, they won't install the meter and your service won't be turned on.

RE: utility PT/CT secondary circuit

(OP)
I'm in Canada.
it will be in dedicated conduit but common duct bank. I contacted my utility meter department, waiting for an answer.

Have you ever seen this type of installation? Power cables and meter cables are going to the same place...so I think it makes sense using only one duct bank.

I will update this thread as soon as I get an answer from utility guys.

Thanks

RE: utility PT/CT secondary circuit

What Bill said is correct, however from technical point of view placing CT/PT secondaries in steel conduit and keeping more than 12 inches of separation, would sufficiently shield from the interferences.

RE: utility PT/CT secondary circuit

Jluc:

I assumed you mean to only share the ductbank not the conduit or ducts with the power conductors. Separate conduit always..as david said.

RE: utility PT/CT secondary circuit

(OP)
rbulsara:

Yes it will be separate conduit for sure, it is part of utility standards, just not sure if I can put these conduits in the same ductbank with power cables, still waiting an answer from utility.

JL

RE: utility PT/CT secondary circuit

Most utilities have a length restriction, which may be exceeded at 100m. I've never heard of running one that far. Seems like you might need to consider some sort of remote reading meter if the utility will allow it.

RE: utility PT/CT secondary circuit

alehman-

As long as the CT burden rating is sufficient, the length shouldn't be a problem. Runs of that long are quite common in substation environments.

Length is not an issue for the PT circuit.

RE: utility PT/CT secondary circuit

scottf, alehman is correct, and your reasoning generally has nothing to do with it.  Cable pulling, bends, that's the way we've done it, securing the run against tampering and etc. are reasons for limiting distance.  Any meter installation away from the instrument transformers needs utility approval from day one.

RE: utility PT/CT secondary circuit

I agree that the CT lead length can probably be handled with proper design. My concern was more along the lines of what David said.

RE: utility PT/CT secondary circuit

(OP)
Utility length restriction here is 150m.

davidbeach you're right, the best thing to do is having your design approved by utility metering guys right from the start.

in my case they accepted it.

thanks for your comments

JL

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources