Weird customer request

[Lady Engineer]

Hi guys,

It's been a long time, but I still come on here a lot to get information but I don't post as much. Since I've last posted, I was hired at a firm that consults for Madison Electric Utility. You guessed it, I'm a utility power engineer, but also I run the department at this firm which does LV also. Big responsibility, but I was able to learn a lot about MV switchgear and distribution in about 4 months. It WAS NOT easy. However, I told them I didn't know how, but they said you'll figure it out! LOL I did, and now I manager Madison Electric's Substation. They buy 34.4KV from JCPL in NJ, and they built their own substations 40 years ago, which transforms the voltage down to 12.47KV.

Now here's my question: I got this request in from client who wanted a primary MV service. They wanted to purchase their own transformers, so they requested Primary 12.47KV service, which connects to their unit substation.

I looked at their switchgear, and made sure the CT and PT ratios, KV, etc. They wondered how come you will not run a Neutral with your 3 phase + G. Yes, our switchgear at the substation is 3ph, 4W, but like a LV system, I see no need to run a neutral with the MV feeder. Now, their substation has a delta to wye connection. Am I missing something, why do they want to bring in a neutral? There's nowhere connect it with a delta to wye transformer? I take that back, you can, but what about the 3rd harmonic? Plus, would they want a wye to wye connection to begin with, especially from a utility?

 

[kingpb]

Ask them for a one-line. It will help you understand what they have, or are planning, and therefore make it easier to answer their request for information.

 

[Lady Engineer]

Hi Kingpb,

Thanks for the reply. That's just it. I have their SLD with their unit substation shown, which asks has a VPI, MV, transformer with aluminum windings. Very standard for us here. They asked for a delta to wye connection. I have no clue why they are requesting a neutral, when they asked for a delta to wye connection for their distribution transformer.

 

[charlie b]

My best guess is that they based this request on a previous project (i.e., they copied another document), and didn't bother to check all the language, to see if something needs to be updated to match the new project. I think you are right, in that there is no purpose to be served by bringing a neutral, and no place to land one anyway. I would find a polite way to ask them to clarify their needs. Oh, and congratulations on your new job.

 

[kingpb]

Without seeing the one-line I will have to defer to your understanding of the situation. However, it would not seem a 4W circuit would be in order based on what you are saying.

Fortunately, as the utility, you are in the drivers seat. Simply tell them what circuit you are going to provide, and let them review it. They will get back with you if there is an issue.

I'd say they are in the position of needing to justify it.

 

[Lady Engineer]

My best guess is that they based this request on a previous project (i.e., they copied another document), and didn't bother to check all the language, to see if something needs to be updated to match the new project. I think you are right, in that there is no purpose to be served by bringing a neutral, and no place to land one anyway. I would find a polite way to ask them to clarify their needs. Oh, and congratulations on your new job.

Thank you Charlie! It's nice to be here again. I'll admit, I come here often, but I usually check the threads to see if there's a thread comparable to my question. I know if I come here, I can get help. I'm not an expert, but I try to fine a solution. It's been a real ride, and I'm very grateful for where I am.

Thanks for the information, from both you and Kingpb! I told them no neutral, but I just didn't understand why they wanted to press the issue.