Electure, I would rather there was a mesh fence above that transformer bank, instead of just a rail. It's rather interesting how the HV comes down into the cage. If that tranny bank was over here it would have 2 cables running down the pole and underground, emerging beside the transformer intakes. We always do things the awkward way here.
Re: Unusual?#118634 10/17/0402:46 AM10/17/0402:46 AM
I work in the 'Waltham Engineering Center', the old 'Waltham Watch Factory' building on the Charles River in Waltham, MA.
This is a fairly old northeast mill building that has been parted up into individual rentals. There are at least 4 transformers feeding the building, with any number of separate 'services'.
Several of the transformers are ground level devices. The one that feeds my lab is at ground level in a fenced in area. The primary is fed from a pole right in the fence area.
The secondary side goes to a set of 4 cables mounted on cross bars on insulators, as if on top of distribution poles, but instead at about 6-8 feet high in the fenced area. There are some 15 sets of conductors all tapped onto these cables, each going to its own weather head into some box or conduit.
Secondary is 120/208 wye; I forget the primary voltage. I believe the transformer is 180 KVA.
There is also a separate transformer mounted on a pole, with a service drop to the building. This is for the elevator, and is a relatively modern addition (last 5 years or so). I don't have any specifics, however I was told that it was 480V service. The interesting thing to me is that only 3 conductors enter the weather head, none tied to the messenger. This makes me think that the service is ungrounded, which I'd thought was not in vogue (still legal, but I thought that some sort of impedance grounding was preferable.)
Re: Unusual?#118635 10/17/0404:28 AM10/17/0404:28 AM
Don't like the conductors supprted on the fence, and the lack of bollards from the angles you shot it at. The combo is dangerous. Back into the fence between the two poles, and knock the conductors off the supports at the same time.
Mark Heller "Well - I oughta....." -Jackie Gleason
Re: Unusual?#118636 10/17/0407:31 AM10/17/0407:31 AM
This setup is between two buildings, & there's another like it for the other building right across the heavily travelled alley. It's wide open to the public (I'll bet Scott35 can identify this location)
There is a chain link fence up on the roof and the pipe that the insulators are attached to is in the clear; (at least until someone hits the fence.) The entire area is wide open on top, however.
I believe the primary voltage is 12KV.
How precarious is this situation really?? Is it just me with my "worst case scenario" thinking again?...S
Re: Unusual?#118637 10/17/0409:28 AM10/17/0409:28 AM
The transformers are not 180 kVA unless they were made as a very special item. The standard three phase sizes are 75, 112 1/2, 150, 300, 500, 750, 1000, 1500, and 2000. Yes they grow them larger and smaller than that but that is all I listed.
I agree that the installation is not good looking and that it is not likely that it would be done that way today (this is an old installation). However, the installation looks safe to me even though it would not meet the rules in the current NESC.
The primary voltage is probably 34.5 kV since there are three bells on the dead-end. It is difficult to judge that aspect without seeing the pole tops. The secondary voltage would be 480Y/277 on the right hand transformer because you can see four conductors hitting the bus head.
I would make a guess that these are in the range of 1000 kVA, 34.5 kVA-480Y/277 V transformers. There are problems with ungrounded delta services but there are advantages as well. It is up to the plant engineers to make the decision with the serving electric utility as to whether or not an ungrounded service would be acceptable. The Soares Grounding book from the IAEI has a very good dissertation about ungrounded services. Note that this is an industrial substation and is probably not exposed to the general public and may even be a customer owned substation (would still be built to the rules in the NESC since the NEC defers to the NESC). The suspicion that it is a customer owned substation is based on the ground level switch handle on the left hand pole, an electric utility would not have that type of switch but the NEC requires it.
The pictures elicit many more questions than they answer. The arrangement looks 20-40 years old, and likely could not be installed nowadays. Metalclad and metal-enclosed gear would be the norm, with a metering section for each tenant if primary metered.
Working clearances inside the fenced area are probably about half of what’s needed, and the air-switch operator on the left pole may serve one or both transformers. Spooky.
Secondary oil containment is not addressed. It was very common for this type of equipment to contain “fire-resistant/safer” fluid (askarel) instead of mineral oil being so close to a structure.
California does not adopt the National Electric Safety Code, but has their own similar “General Order 95” and G.O.128 for >600-volt systems.
The site would be an insurance-underwriter’s nightmare [or red woody!] ;-)
I'll get a couple more pics to clarify things. This is a large (very) electronics store. The electrical is pre-'70. (believe it or not, I remember it ) At one time it was part of a lighting fixture company that still occupies the building across the alley. The installation is utility owned. Anaheim, CA has its own distribution system, and the low mounted switch handles are common all around town. Pri Voltage is 12KV (per sign on gate).