Pole Mounted Transformer

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Hameedulla-Ekhlas

Hameedulla-Ekhlas

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Greeting all,
I am asking too many question hope no one mind it but I need your help and explaination.


I have one pole mounted 630kVA transformer in one project. The existing final load( including demant factor) is 580kVA connected to this transformer. I want to connect some new load to this transformer.
The total final load (include demant factors) equals to 60 kVA.

I know nothing operate to its 100% effecieny and if I connect new load to this transformer.

what will happen please advise the disdvantage of this?
 
Sorry there was a mistake in explaination please read the below the correct one.


I have one pole mounted 630kVA transformer in one project. The existing final ing load( including demant factor) is 580kVA connected to this transformer. I want to connect some new load to this transformer.
The total new final load (include demant factors) equals to 60 kVA.

I know nothing operate to its 100% effecieny and if I connect new load to this transformer.

what will happen please advise the disdvantage of this?
 
The distribution transformers we have here could handle this 1.6% overload practically forever given a few caveats. One being that the transformer will have a sufficient cool-down period where it is not overloaded. The other is that the transformer is not already being subjected to abnormally harsh environment conditions.

There are formulas available to calculate the loss of life incurred by overloading a transformer. Usually, the cool-down period is sufficient to recover the life.

You might notice a drop in voltage regulation because you will be pushing the transformer to its limits.

Also, you have to consider that the load you will be applying will not be at the peak value all the time. We will sometimes let the demand peak up to 140% of rating before change-out, depending on the load.

They can handle a 300% overload for a real short period, and 200% for a little longer. I usually don't even worry about a 5-10% overload.
 
Hameedulla-Ekhlas said:
Greeting all,
I have one pole mounted 630kVA transformer in one project. The existing final load( including demant factor) is 580kVA connected to this transformer. I want to connect some new load to this transformer.
The total final load (include demant factors) equals to 60 kVA.
Click to expand...

Is the 580 KVa a measured demand or calculated? Either way the added 60 KVA wouold not cause a problem for the transformer. Check the secondary conductor ampacity.
 
100220-1026 EST

Are you saying that you will add 60 KVA to an already exiting 580 KVA making the new total 640 KVA? Therefore this exceeds the 630 KVA rating of the transformer.

Because a transformer is rated at 630 KVA, does not mean that if load it to 631 KVA that it instantaneously blows up. The rating is based upon a lot of factors. Probably the major consideration is temperature.

The average life of many components is determined by their operating temperature. This is an absolute temperature, not a rise. The absolute temperature is a result of the ambient, thermal transfer, and temperature rise. Further there is no precise life. Rather the life is something that has a random variation dependent on many factors.

Larger objects, like transformers and motors, have a lot of mass associated with the amount of power dissipation within the device, and therefore have a moderately long thermal time constant, minutes to hours. Therefore can tolerate short reasonable overloads with no great problem.

On the other hand transistors have very short thermal time constants, and somewhat precise voltage breakdown points. Thus, these devices can not stand overloads for very long. Like milliseconds to seconds.

What are the actual loads on your transformer now and how do these vary with time. What is your ambient temperature profile over a year. This information and maybe more data on the transformer may allow you to make an intelligent decision.

.
 
Wow! It has to be hung on one fat pole to support that transformer which must weight over 3500# possibly 4000#. A 500kva is usually on the to end.
 
templdl said:
Wow! It has to be hung on one fat pole to support that transformer which must weight over 3500# possibly 4000#. A 500kva is usually on the to end.
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I'm guessing 5000-5500 lbs.

A 45ft class 3 (12" dia) could handle the transformer alone, but you add another 5,000-8,000 lbs of vertical load for a dead-end pole and you would need at least a class 1 (13.7" dia) up to a class H1 pole (14.5" dia)
 
jghrist said:
The 630 kVA transformer would be 3? and could be smaller than your bank of 250s. This is a common size overseas.
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Didn't know that.

We either have 3 phase banks using 3 single transformers or 3-phase pads on the ground (sometimes 3 oh transformers on the ground in an enclosure). I have seen some banks of padmounts but it is rare around here.
 
I've seen many instances where a bank of 3 rather large transformers was mounted on a platform hung between 2 poles. They looked like autotransformers used to boost distribution voltage for long rural runs.
 
kbsparky said:
I've seen many instances where a bank of 3 rather large transformers was mounted on a platform hung between 2 poles. They looked like autotransformers used to boost distribution voltage for long rural runs.
Click to expand...
We do that for regular transformers sometimes.

I think it works great for voltage regulators as they are sometimes very heavy and would otherwise be on several different poles. There are some nice aluminum platforms that look good.

I don't like the look for a regular service but sometimes you have no choice.
 
that type of construction is what we call an "H-Frame". in your case this would be a modified h-frame. also, looking at your 1-line (some others have alluded to this), you aren't loading this at 100%, are you? you need to add in a diversity factor. that is determined by what <em>TYPE</em> of load you have connected.
 
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