Medium voltage switches and transformer

[anbm]

I have little experience with medium voltage stuffs, I have these below questions hope you guys can clear my head. I appreciate that.

We have a project where we run new 15kV feeder from existing manhole at site to new medium switch pad. From this switch pad, we come out with (2) separate feeds, each feed goes to a different medium voltage transformer and then steps down to 480V switchboards.

1. What is medium voltage switch pad (I am not sure I call the right term for it) above? Is it something like a medium voltage metal enclosed box with two medium voltage fused switches or medium voltage breakers? Does anyone has an example pictures of this switch box? Please list some popular manufacturer who makes it.

2. Are there any specific codes, rules to install above medium switch box? Does it need to be inside the vault? Required clrearance?

3. Does medium voltage transformer always come with primary protection as fused switch or breaker? Who makes these transformer?

4. What is ATO switch? What does ATO stand for? Is this medium voltage switch that allows us to select between 2, 3, or 4 available voltage sources? Which manufacturer makes these ATOs?

5. Is it electrical engineer's responsible to specify above medium voltage switch pad, ATOs and transformer or by utility company person?


Thanks!

anbm

 

[waross]

Do you mean an Automatic Throw Over? The term is new to me. Is anyone else familiar with this acronym?

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

 

[Zogzog]

ATO is new to me too but good guess I think Waross.

Anbm, your questions are way to vauge and can not even be started to be answered without knowing where in the world you are located.

Your manufactures will vary depending on your location also but your best bet is to stick with the same one for all of the above. ABB is a good one that makes all of that stuff and is worldwide, although more popular in Europe than in North Amercia.

 

[anbm]

Zogzog, I am from Dallas - Texas. can you point out which term is vague to you? (-:

 

[gunax]

since you run out the medium voltage feeder, it depends on your transformer rating, you would need transformer protection either fuse or circuit breaker at the source side of the transformer which will protect the system or transformer from any shortcircuit at downstream of the fuse.

You may ask S&C or ABB, Seiemens related on this matter.

I guess this is what you need

regards

 

[Zogzog]

Ok you are in the USA, that is a start. Square D, ABB, Cutler Hammer, GE, and S&C all make the switches you are looking for, go to any one of thier websites and look at MV switches, you will get your answers there.

ABB basically makes all of the transformers, ither OEMS buy the cores and put thier own skin and accessories on them.

Rarely do you see a MV switch that can select multiple voltages.

Dallas just happens to have 2 of the best MV training schools in the country for this type of stuff. Shermco and AVO, you may want to look into some classes.

 

[anbm]

ATO = auto transfer

I think what I am looking for medium voltage interupter switch, is it rated at max. 1,200A for any medium voltage range?

 

[Morrand]

I'll try to answer based on what I've designed on previous jobs:

(1) I think has been answered above.

(2) A vault is probably not required unless this is oil-filled gear, which it most likely is not. Assuming this is not utility-owned, check Article 490 of NEC for some information.

(3) Some transformers do have built-in protection, but many do not. The better practice may be to put your protection into the switchgear, in order to protect each transformer from a cable fault on the other's feed. You may also have a better selection of transformers available that way.

(4) ATO stands for Automatic Throw-Over (very similar to an Automatic Transfer Switch, though where I come from we draw a firm distinction between the two). It does allow you to select between two sources, but it also has the ability to perform this function automatically when one feed fails. The details of how it operates (such as whether both feeds are normally serving load at the same time, or whether the ATO switches itself back automatically) are often specified by the serving utility. These are made by some of the same manufacturers listed previously.

(5) A engineer must specify all of this. Who does it is usually determined by who will own and operate it: if the utility owns all of the equipment, they should specify all of it, and all you will need to do is to get their requirements from them as to clearance, required facilities (like concrete pads and interconnecting conduits) and anything else they want. If the utility customer owns it, the customer's engineer must design it, usually to utility standards. Call the utility and ask them what they want to do. (If they are specifically calling for a "switch pad" by that name, chances are that they intend to set the switchgear themselves, but you'd better find out for sure.)

 

[anbm]

Morrand,

You know any free online resource describing more details about ATO switch? Thanks!

 

[alehman]

http://www.sandc.com/products/padmountedgear/pme_st.asp