Utility transformer problem

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TGE02

Member
A buddy of mine owns a building in which he runs a plastic molding injection business out of. He has quite a bit of 3 phase machinery and single phase heating elements that he runs constantly, as well as high bay lighting and some office lighting and what not.

The utility transformer is on site and it feeds a 3 phase, 277/480 volt, 600 amp main switch board in his electric room. He has a 145 kva transformer that is fed from his 480 panel that feeds his 120/208 volt panels. Recently the utility transformer blew a fuse, it was replaced. Then the utility transformer stopped working all together and was replaced. The utility company informed him that he will have to pay for their new transformer due to their belief that his 145 kva transformer was the cause of their equipment failure. They gave no explanation as to how or why they believe this to be the cause.

Does this sound right? He never had any problems with the breaker tripping on the primary side of the transformer. How would the utility come to this conclusion?

Any input is appreciated and I apologize if I posted in the wrong forum. Thanks.
 

tryinghard

Senior Member
Location
California
Welcome TGEO2,
Commercial utility service contracts are often like this. The customer often has to supply their load calculation to the utility either by their own hand or through a contractor/engineer. The utility sizes their supply based on this calc. If this is an old building that has morphed over the years with items added without informing the utility (or permits) at some point their transformer can be undersized. The utility usually has fuses at the primary cutouts and sometimes fuses in their secondary pad mount cabinets but other than that it’s up to the service disconnect to provide overcurrent protection. Your friend needs to see their contract agreement with the utility, but its pretty common the utility charges to upsize service.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Why should the utility cover its losses, if they can convince a customer to do it instead?
You might be surprised at how many customers would not fight this claim.
 

TGE02

Member
Welcome TGEO2,
Commercial utility service contracts are often like this. The customer often has to supply their load calculation to the utility either by their own hand or through a contractor/engineer. The utility sizes their supply based on this calc. If this is an old building that has morphed over the years with items added without informing the utility (or permits) at some point their transformer can be undersized. The utility usually has fuses at the primary cutouts and sometimes fuses in their secondary pad mount cabinets but other than that it?s up to the service disconnect to provide overcurrent protection. Your friend needs to see their contract agreement with the utility, but its pretty common the utility charges to upsize service.

Thanks for your response. The utility transformer was installed in accordance with the original 480 service to the building, the service was never upsized and was not running at or near the 600 amp capacity. There was no need to upsize the service.

Do you have any idea how they would come to the conclusion that my friends 480->208 volt transformer caused the problem in the utility transformer?
 

topgone

Senior Member
A buddy of mine owns a building in which he runs a plastic molding injection business out of. He has quite a bit of 3 phase machinery and single phase heating elements that he runs constantly, as well as high bay lighting and some office lighting and what not.

The utility transformer is on site and it feeds a 3 phase, 277/480 volt, 600 amp main switch board in his electric room. He has a 145 kva transformer that is fed from his 480 panel that feeds his 120/208 volt panels. Recently the utility transformer blew a fuse, it was replaced. Then the utility transformer stopped working all together and was replaced. The utility company informed him that he will have to pay for their new transformer due to their belief that his 145 kva transformer was the cause of their equipment failure. They gave no explanation as to how or why they believe this to be the cause.

Does this sound right? He never had any problems with the breaker tripping on the primary side of the transformer. How would the utility come to this conclusion?

Any input is appreciated and I apologize if I posted in the wrong forum. Thanks.

I would like to assume that the busted fuse was replaced by one of the utility guys, right? As a has-been utility worker, I am surprised how the utility guys assessed the fuse blowing and just outright replacing it . If I were to do it, I would never leave the premises without measuring the load if it was within the capacity of the utility trafo, etc. , etc. Having said those, there should have been conversations done with respect to what the cause/s of the fuse blowing was between the consumer rep and the utility men; if only to prevent damaging the service transformer. If that talk didn't happen, a load survey can determine whether your friend's load was upped without informing the utility (meaning, your friend is at fault or not). And as mentioned by the other poster, please refer to the original contract for guidance.
 

mivey

Senior Member
Sounds goofy to me. They should protect their equipment. Unless you are requesting a non-standard connection or delivery, the regular rate should cover anything you are required to pay.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Sounds goofy to me. They should protect their equipment. Unless you are requesting a non-standard connection or delivery, the regular rate should cover anything you are required to pay.
In general utilities do not protect transformers of this type. Their primary OCPD is sized to protect the primay distribution system and not the transformer itself.
 

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
Additionally, I would add that the Utility does not always supply the full sized transformer, based on their own internal load factor data.

If the 208Y/120V is fed from the 480Y/277V, and the building main is sized properly for the service, the finger needs to point at the utility.

Ask them what size transformer is installed, and if it was new when it was installed. Transformer winding failures do occur, the fuse blowing may have been the precursor.
 

erickench

Senior Member
Location
Brooklyn, NY
Question: Your friends transformer is it newly installed or has it been there for quite some time?

If it's been there for quite some time without an incident then something else may be causing the utility transformer to blow. Did your friend check his transformer to see if it's functioning properly? There may be a short in the primary causing an overcurrent condition.
 
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mivey

Senior Member
In general utilities do not protect transformers of this type. Their primary OCPD is sized to protect the primay distribution system and not the transformer itself.
I would say it is more a function of size and service characteristics than transformer type. As the transformers get larger, and as the potential for large secondary faults increases, the tendency is to lower the fusing ratio. It is false to say they are not protecting the transformer. However, they are pushing the limits on the high fusing ratio side.

However you see it, that has nothing to do with the responsibility of protecting the transformer being on the utility. The choice of the utility to raise the fusing ratio to make use of the over-load capabilities of the transformer is weighed against the service type and the characteristics of the load.

Unless the customer is abusing the system with a high number of faults or something similarly severe, the POCO should pay the price for hedging on the transformer protection. I saw nothing in the OP that indicated the customer was being abnormally abusive to the supplier, certainly nothing that could not be expected.
 

TGE02

Member
Question: Your friends transformer is it newly installed or has it been there for quite some time?

If it's been there for quite some time without an incident then something else may be causing the utility transformer to blow. Did your friend check his transformer to see if it's functioning properly? There may be a short in the primary causing an overcurrent condition.

I believe the utility transformer had been there since the building was originally built in the 70's. The 480->208 transformer in the electric room seemed to be functioning properly when the utility when down. I would think if there was a short in his transformer it would have tripped the breaker on the primary side but that never happened. The utilities fuse blew while everything was functioning normally inside the building, running well below the 600 amp capacity of the MSB.

Keep in mind this all happened about 2 years ago and the utility is just now handing him a bill for $35,000.00!
 

mivey

Senior Member
Keep in mind this all happened about 2 years ago and the utility is just now handing him a bill for $35,000.00!
I would not pay it without some supporting documentation that could prove the money was owed. Is the POCO investor owned or not? Can you get a copy of their rules & regs concerning line extension policies?
 

tryinghard

Senior Member
Location
California
Thanks for your response. The utility transformer was installed in accordance with the original 480 service to the building, the service was never upsized and was not running at or near the 600 amp capacity. There was no need to upsize the service.

Do you have any idea how they would come to the conclusion that my friends 480->208 volt transformer caused the problem in the utility transformer?
When I say “upsize service” I mean the utility either qualifies their existing XFMR or replaces it with larger as well as their conductors. Your friends XFMR is downstream of the service disconnect but the utility doesn’t necessarily size their service to the "service disconnects" size; they do size to the calculated load at minimum though - the question to ask the utility is: specifically what protects your XFMR from overload (line cutouts/secondary fuses/internal OL's/service disc OCPD)?

It would be remote for the premises XFMR to fail in such a way to increase amperes long enough to damage the utilities XFMR. The premises XFMR is 2.3:1 ratio (480:208) I suppose its secondary could lose a winding or two causing lower voltage higher amperes but this would mean one or two windings welded together with no other damage and all this should open the premises XFMRs protection.
 

brian john

Senior Member
Location
Leesburg, VA
I'd fight them every inch of the way, ask for documentation, ask for all previous bills, demand they bring the customer service rep (in our area none existent these days). Make them prove this.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
The utility company informed him that he will have to pay for their new transformer due to their belief that his 145 kva transformer was the cause of their equipment failure.
Not without the previous (to the failure) year's POCO demand records proving the demand drastically exceeded the load calcs they were given when the service was first engineered.

I'd fight them every inch of the way . . . Make them prove this.
Absolutely! The mere existence of a customer-owned transformer is no evidence at all.


Added: If the proverbial shoe were on the other foot, they'd demand all kinds of proof, and even then fight it tooth and nail.
 
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mivey

Senior Member
TGE02,

I would sure be interested in seeing any "evidence" the utility provides. Under normal circumstances, they have a pretty steep hill to climb.
 

kwired

Electron manager
Location
NE Nebraska
I will also add that if that transformer was installed in the 70's it has probably outlasted its expected lifetime. I believe most POCO's have distribution charges of some type on their monthly bills. These charges are supposed to be for covering cost of maintaining equipment.

Many of them also charge a penalty if you do not use enough power because they have idle equipment not being used to its potential but they also charge you a penalty if your load is too high because it is taxing to their system. If the transformer was overloaded they should have known long ago if there was too much demand for the equipment and done something about it then besides bill you for being over on demand.
 

mivey

Senior Member
Many of them also charge a penalty if you do not use enough power because they have idle equipment not being used to its potential but they also charge you a penalty if your load is too high because it is taxing to their system.
In the general case, I would call it a rate component rather than a penalty. There are three main costs and rate components:
Customer charges (based on your presence, not usage - like reading a meter, printing a bill, etc)
Demand charges (based on how fast you take energy from the system - speaks to equipment size)
Energy charges (based on on how much energy is consumed - like fuel costs)

These combined can make a rate that is sensitive to load factor and can result in higher average cost per kWh for those that have poor utilization of the equipment (i.e. a low load factor).

That said, there are special cases where the customer has a contract in place in which they have agreed to their load being a minimal size. There can be a penalty fee written into the contract if they do not reach the minimum load by the specified time. They may also have agreed to a minimum billing demand instead of a specific penalty charge.
 
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