12470 feeds two 2500 kva transformers. Service point Line side of disconnect. So under NEC . One disconnect for both transformers or one disconnect for Each transformer?? If it was Power Co.owned they'd use one for both . But nec ???
230.200 NEC"s a start. Also another interesting Question are disconnects grounded?? If so How??By the way theses switches are outdoors. about 150 ft from transformers.

Okay Ernie— The rules for less than 600v. apply based on 230.200. The disconnect(s) will be "Service Disconnect(s)" and there are no Service Entrance Conductors. The overcurrent protection must be an integral part of the disconnect(s) or be immediately adjacent 230.91. The conductors feeding the xformers are feeders and the rules for overcurrent protection found in 240.101 apply. As for the grounding, the GEC will be the ground for the Service Disconnects and will be sized per 250.66 Note 2. As for 1 or 2 Disconnects I think either would work and which ever would cost less would probably prevail.

This is my opinion and I hope I've not missed something.
Hey Ernie- You going to Holland?

Ernie— After reading your post and my response, I think I might have assumed something and maybe my answer was not appropriate. Are the transformers customer owned? Where is the disconnect switch(es) in the system? What is the voltage Primary & Secondary of the transformers?

George
Power Co. Line 12470 three phase . Customer owns both transformers. Disconnect Switch or switches (fused) where Power Co. Comes off Pole . Aprox. 100 ft to transformers. Secondary of transformers 480/277.

Ernie- If the switch(es) are customer owned I'm sticking with my answer. Still not sure but since you said the "Service Point" is the terminals on the line side of the switch(es), it sounds like the switch(es) are customer owned.

Service point top of Pole at utility co. cutouts.

Ernie— I'm starting to get the picture now with your added information. Your first post said the Service point was the "line terminals of disconnect".

The pole top cutouts do not qualify as a Service Disconnect based on 230.70. You were saying that the Service Point is at the line terminals of the disconnect switch - apparently the pole top cutouts is what you were referring to. This would mean the conductors after the pole top cutouts are customer owned and the the conductors are Service Entrance conductors that need a Service Disconnect that complies with 230.70. I suspect that the cutouts are utility owned.

I don't see anyone making any comments so maybe the answer is forthcoming from others. I've never had to inspect a service like this so maybe I can learn something.

Are there individual fuses for each transformer per(A)?

If the conductors to each transformer are feeders are they protected as required by 240.100?

If the conductors to each transformer are service conductors are they protected per 230.208?

At the service disconnect point does the disconnect device simultaneously open all ungrounded conductors per 230.205?

Does the service disconnect have visible blades per 230.204?

See Page 230.200 Exhibit 230.31. Thats the way it is. the disconnects are remote from the transformers line sideas per 230.204 (B)location per 230.205(A) which refers you to 230.70 (A)
Load side of transformers Disconnect switchs in Building Nearest point of entrance 240.21 (C) 4.

Ernie I guess you meant page 155 in the '05 handbook. This is what I said earlier— The Service Disconnect is missing in your posted question. You will need a Service Disconnect and fuses just like what is shown in Fig. 230.31
Must meet the requirements for "Readily Accessible" per 230.70(A). The Depending on some of the other factors ie: wire size and fuses and ownership you might need two switches and two sets of fuses.

Customer owned transfromers need overcurrent protection per article 450.

Single phase cutouts cannot be used as the service disconnect device. Although they can be used to provide overcurrent protection for the service, feeder conductors, or transformers.

As George keeps saying, above 600V the service disconnect must be a multi-pole device. Also,location is not as important as is the type of equipment.

Page 155 2005 N.E.C. Exhibit 230.31 Code handbook Clearly shows secondary protection for the transformer is NOT required till the feeders enter the Building. The Conductors must be protected as I stated before in 240.21.
This is a common pratice done on most college campuses.(notice no big disconnect switchs by the transformers next to the buildings)read 240.4 F . 450.3 refers you to article 240 in FPN"s for overcurrent protection of conductors.I agree the Primary must be protected by a serice rated 3 pole fuseable disconnect but a didconnect is NOT required on the secondary side of a HV to LV transformers located remote and outside of a building.

Both load breaks should be fused for protection o feach transformer, and grounded. There are also termination issues here and testing requirements. Either you or the owner should have a certified testing company run acceptance testing on this installation.

There are about 10 NETA companies in Michigan, 5 in detroit alone. You can fond one at www.netaworld.org

Usually High Voltage stress cones Kits on switchs, High Voltage elbows on Transformers (most so easy now compair to 20 yrs back), High Pot the cables to factory specs. Most of this is done in house with a Qualified Electrical contractor. I find Most Electrical inspectors and electricans have a Very limited info on any thing over 600 volts.
Almost every College has HV switchgear in a seperate Blg. Fused then cpl . feeders< then taps off thoses feeders in manholes , then to transformer in or right outside of each building , then to 480/277 to gear in room. This is all maintained and owner owned, from the line side of the ist set of switch gear thurout the campus. Paper mills are the same .

DC Hipots are not acceptable anymore, considered a destructive test by the IEC, IEE, and NETA standards.

A AC VLF, Tan Delta, or PD test would be acceptable.

I guess I am confused. I thought your original question was dealing with the transition from the utility to the primary of customer owned transformers, now you are including their secondaries in the discussion.

What questions are you still working on?

The Original Question was about the service disconnect switches ect. But when Feeders were brought up I just added additional info. As far as Hi potting Most factory specs. usually Put a limit on the voltage you can use as far as I've always know.