Ambient Current/Power in Large Transformers

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Sparky599

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Hi Folks,

I posted some time back on/about the Jamesburg Earth Station tryiing to Identify a rogue load that is causing over $1500 a month electrical bills, at the 4 acre earth station site. The site is dormant, not "on" currently, but a big dish, and 20,000 square ft of equipment space.
If you want to see it, Check out: http://www.jamesburgdish.org

I am now looking at/for power consumption in the site transformer itself.
The transformer is rated for about 1 megawatt max power consumption, but hasnt done that for years.

I wonder what the power consumption is on a 1 megawatt transformer that takes distribution voltage (~12 KV) and outputs 480 volts to the station.
Wnen the station is dark, with minimal loads, what would someone expect that the unloaded transformer would draw, ambient?
We have > $1500 per month in electrical bills, and we think more like $100 per month is actually used. 1500 per month is $50 per day, or about 500 kwh/per day, or 20 kwh per hour, or 20 kilowatts. Can the transformer eat that up as waste energy?

The 1 megawatt transformer is about 8 ft tall, 15 ft long, and 6 ft wide. The ins and outs are underground, so I cannot see them, and dont yet have a diagram of the power system on the site.
 
In my opinion, the best thing to do is monitor current real-time and turn off each disconnect, one at a time, while watching the current.
 
Have you checked with the utility regarding the bill? Is your customer being charged for a demand in kw or kva? Is there a minimum charge per month? Have you put a clip on meter to see if there is any amperage draw at no load? What has been the maximum demand at the site?
 
Can you scan your electric bill and post it where we can see it?

How many other transformers are in the facility such as 480/ 120/208?

Are you charging all of those battery racks?
Are they operating equipment through inverters?
 
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Sparky599 said:

I am now looking at/for power consumption in the site transformer itself.
The transformer is rated for about 1 megawatt max power consumption, but hasnt done that for years.

I wonder what the power consumption is on a 1 megawatt transformer that takes distribution voltage (~12 KV) and outputs 480 volts to the station.
Wnen the station is dark, with minimal loads, what would someone expect that the unloaded transformer would draw, ambient?
We have > $1500 per month in electrical bills, and we think more like $100 per month is actually used. 1500 per month is $50 per day, or about 500 kwh/per day, or 20 kwh per hour, or 20 kilowatts. Can the transformer eat that up as waste energy?

The 1 megawatt transformer is about 8 ft tall, 15 ft long, and 6 ft wide. The ins and outs are underground, so I cannot see them, and dont yet have a diagram of the power system on the site.
Click to expand...

I assume this is a 1500kVA transformer, or larger. Transformers are pretty efficient machines, but the core losses (Hysterisis and eddy current) are the same no matter what the loading is (Copper losses change with load). Your core losses can be calculated from test data or measured easily but there is no way to tell you what they are from the data you provided.

Lets say (Total guess here) that your 1500kVA transformer has 2% core loss (Typical), thats 30kVA, or about 25kW assuming you are paying some commercial rate, say $0.07/kWH thats $1.75/Hr or $42/day or $1,260/Month.

If you will never need 1MW again, you can replace this transformer with a smaller unit, less core losses, will eventually pay for itself. How long that takes would require more info, but will be easy to figure out. $15k/yr can pay for a small transformer in no time.
 
Sparky599 said:
The 1 megawatt transformer is about 8 ft tall, 15 ft long, and 6 ft wide.
Click to expand...

That would be, by some margin, the largest 1MW transformer on the planet. A 1MVA should be an easy fit inside a six foot cube.

Unless its a "packaged substation" (or whatever its called in USAville) which is a transformer and all the associated switchgear is a single assembly that comes straight from the factory complete.

If your power requirements have dropped drastically I'd recommend you get the PoCo top supply you with 480V, that way they pay to keep their transformer warm, not you.
 
No load losses on a recent 3000 kVA 24940-480 volt padmount transformer are 3,837 watts. This would be 2800 kWh per month or $280 at $0.10 per kWh.

Are you sure that you aren't paying a large contract demand charge to the utility? If you are, you might be able to get that reduced.
 
Large Transformer Photo; Idle current question

Large Transformer Photo; Idle current question

QUOTE=bob]Lot of posts to your question. Please return.[/QUOTE]

This is a really rich resource for answers...Thanks for the helpful replies.
I think the "core" problem is as, some have said, that the idling losses for a transformer like that are, indeed in the range of losses we seem to be experiencing and paying for.

I will try to find a billing statement, and will post details if successful.

I enclose a partial view of the transformer in a photo, here. I think the transformer is indeed a multi component system, taking the 12 kv or so to 480 V. My guess, not having seen the inside is there are multiple taps, allowing different configurations between the primary and secondary.
Unfortunately, I am 210 miles away, and cant get down there (near Monterey CA) to look more closely.
The size of the cabinet is actually larger than I mentioned earlier, just from looking at the photo.
To the right of the photo, you can see a concrete pad, on which was a large diesel power backup generator, and fed the building's UPS, consisting of switching equipment, and a large room of Lead Acid cells.
The former COMSAT site could not tolerate any down time, for any reason, esp possible mains failure, due to the very heavy traffic load it was carrying between North America, and the Pacific/Asia markets.

One of the now retired technicians who worked at the station, said the transformer actually replaced an even larger one in the past, that had fooling fins visible on the outside.

Thanks, guys, All the best, Sparky599..
The Power transformer for Jamesburg is partially visible on the left.
Viewer.aspx
 
I guess at this point I dont understand what your question is, you have near expected losses for a transformer of that type, cant shut it down to do further testing (Or replacement/repairs). Are you just trying to save money on your electric bill? Have some power monitoring done to figure it out.
 
Sparky599 said:
QUOTE=bob]One of the now retired technicians who worked at the station, said the transformer actually replaced an even larger one in the past, that had fooling fins visible on the outside.

Thanks, guys, All the best, Sparky599..
The Power transformer for Jamesburg is partially visible on the left.
Viewer.aspx
Click to expand...
A couple of points to add to/corroborate previous posts.
The earlier unit with the cooling fins was probably an oil cooled transformer.
From the pictures, the present unit looks as if it might be a dry type, possibly cast resin, together with some switchgear.
That could account for the rather large enclosure.
An oil cooled unit could be, as dbuckley suggested, fitted within a 6 ft cube. We are currently bidding for a project which would include a 1250kVA transformer. The largest outside dimension is the width which is 1706mm (about 5.6 ft)
 
One other thing...how hot is it getting with respect to ambient. If you can't measure the inputs and/or outputs easily, this is one way to see that energy is being wasted through the transformer. The input energy has to go somewhere, either it gets converted to electricity on the secondary, or gets frittered away as heat and/or noise.
 
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