Secondary side of a utility owned residential distribution transformer safety issue

[jakedoub]

Hi everyone,

I have moved into a new jurisdiction to serve as an inspector/plans examiner/building official (about 750 miles from where I was living) and am learning about "how things are done" in this new area. After performing an electrical inspection, I headed back to my office. On the way back, I came to a stop sign and was surprised at what I saw (picture is attached). To make a long story short, a pad mount transformer sits on a property. From the pad mount transformer, the secondary is run in about 15' of conduit and is duct taped to the top of a palm tree. From that point, it crosses over the driveway of the property, rubs underneath of a large oak tree branch, and then is duct taped to the top of another palm tree at a height of about 27', and is then run back down again in conduit. From this point, the conductors are terminated in a ground level box and run to the meter enclosure. This work was done by the utility company and was considered an emergency repair four weeks ago. No one is living in either home affected by this condition.

I immediately stopped in and called the utility company to disconnect the power due to an unsafe condition. When the utility company showed up, I was given the "we've been doing it this way for thirty years speech" and the "are you telling me that we also need do disconnect every house in this community that is done like this" and the "we're just trying to keep these contractors working so they can feed their families" speeches, which I have little use for when work is done in this manner. One of the linesman got on the phone to his boss while I was taking to the other linesman and describing what was wrong with the installation. After the other guy was done talking to his boss, he informed me that his boss said "the inspector has no business inspecting anything we do because we are a public utility, he belongs inside the house inspecting the electricians wiring". This is fine, it's not my first run in with a utility company, and I let it roll, figuring I would talk to this guys boss when I got back to my office. The linesman I was talking to said there is no danger if something were to happen since the transformer comes with a 3amp bayonet fuse to protect against any faults on the primary and secondary. I asked how does he figure that one? No path (other than the grounded conductor) back to the transformer, and I tried to explain that the bayonet fuse protects on the primary side against any internal faults to help reduce the chances of the transformer exploding, and it would protect against line surges as well. We go round and round for a few minutes with no positive results. I go back to my office, call the guys boss (Line Supervisor) and leave a message. He doesn't call me back at all which is not surprising.

I then call the Public Utility Service Commission and ask if they regulate electric co-op's and they say no and give me a number to call the Office of Regulatory Staff (ORS). The ORS were actually very pleasant to speak with and tell me that they have no governance over a co-op and that a co-op is self regulating and has their own by-laws and basically receives no oversight from any type of governmental agency. The guy from the ORS said he was going to speak with their attorney on staff and a few other internal staff members to see if they can help point me in a better direction. The guy from the ORS called me back and left a message stating he is still looking into it, but doesn't have any help as of yet. From my past experience utility companies use the IEEE NESC as their installation manual, and I no longer have access to one. I can take a bet and say this is not considered an emergency, nor a safe installation. I ordered a copy this Standard and will have it tomorrow.

I inform my boss the next day of what is going on. My boss calls the line supervisors boss and asks when this will be fixed. He informs my boss that it will be at least another two weeks. My boss says ok, and that is it. He basically told me to let it ride, which I have a hard time doing.

I do not have much experience with utility distribution, but I can make some assumptions. The first assumption would be that the 3amp fuse in the transformer protects only the primary side. If a fault were to occur on the secondary, the fuse would not trip. Am I correct in this? If I am incorrect, then I would have to then assume that either a high current from a fault condition on the secondary, will also induce a high enough current on the primary windings to trip the primary fuse, but my guess is that it would take a substantial amount of current flow on the secondary to active the primary side fuse. If this is the case, would someone be able to show me the calculation for determining this, based on assumptions of typical transformer impedance etc

A second question would be, if there is a fault on the secondary, what would have to happen to clear the fault and how much current would it take? The linesman I spoke with said the primary is 14.4KVA. I am not familiar with utility transformers, but I have never heard of a 14.4KVA stepped down to 120 in a single pad mount transformer. The transformer dimensions are about 3'x3'x3'.

A third question is, with no support from my boss, and little response from anyone, what suggestions would anyone have? The area I work is also filled with extremely wealthy people, who are able to buy 3 million dollar homes with cash. The reason I say this is because the board members have little concern about the building department. This is also a higher foot traffic area so safety is a pretty big concern. We are also in a 147 mph wind zone and seismic design category D2, which means very bad and we just started hurricane season, so it makes me nervous.

Any suggestions would be greatly appreciated.
Jake

 

[ActionDave]

Welcome to the forum.

Hang out with linemen long enough and you will soon wonder why we have not all been blown up. I'm a brother in law to two of them.

Concerning your question about a primary fuse blowing on a secondary fault....the fuse will blow, it just has to be a big enough fault. I saw it happen once when there was an accidental short across the line side of a meter socket. Three amps at 13,000 volts equals what at 240 volts?

 

[Fulthrotl]

A third question is, with no support from my boss, and little response from anyone, what suggestions would anyone have? The area I work is also filled with extremely wealthy people, who are able to buy 3 million dollar homes with cash. The reason I say this is because the board members have little concern about the building department.

Any suggestions would be greatly appreciated.
Jake

you noted an unsafe condition, and reported it to the powers that be.
the powers that be made a yada, yada, yada noise and went back to
their nap.

short of rewiring it yourself, i'd say you are done.

one thing about extremely wealthy people being nearby, if it faults
and burns stuff down, wealthy people have no reluctance to spool
up their wealthy lawyers to create a snit. ohm's law showers sparks
on the well heeled and unwashed with equal fervor.

 

[JRW 70]

NESC

NESC

As far as I know, this practice is not allowed
even for temporary repairs ( if they are truly
using the NESC in any of the additions I am
familiar with ). In the utility I work for we try
to do complete rebuilds after storms, even if
outside utils. or contractors are hired. I know
because of watching over a group of contractors
to make sure they built it to company policy.
I mostly do testing at plants and sub stations,
and can tell you that the fuses are to prevent
transformer failure in a catastrophic way and
most importantly keep the upstream lines
on. So what they said about secondary
protection is definately questionable.
If you want results, then contact someone
higher up in their company structure.
(for example : if they have a district
engineer or someone who is responsible
for how they do their buildouts and
set the requirements for coordination
of fusible links up to reclosers to sub.
breakers. That is who you would probably
get action from)

And litigation always gets attention too.

There is a lot of terrible work done as well
as the utmost of quality. If this isn't your
fight, sometimes we just have to learn to
let what we cannot control go and not bother
our minds with things that there is little or
nothing we can do about it.

JR

 

[kwired]

You are trying to change something outside your jurisdiction. Not saying it is wrong to give them a piece of your mind, but your inspector title means little to them.

Fuses only protect the equipment - to some degree, but the 3 amp primary fuse will not even flinch when the little necessary secondary current is flowing that is needed to electrocute someone.

Litigation will change their ways the fastest in these kinds of cases, but sadly it usually takes someone getting killed before that happens.

 

[gar]

150619-0814 EDT

jakedoub:

A closely coupled transformer (normal iron core transformer) reflects voltage and current between the primary and secondary by the turns ratio. Your transformer has a turns ratio of 120 to 1 between the primary and 1/2 half of the secondary. Thus, from primary to secondary the voltage is reduced by a factor of 120. The current is an inverse relationship. Thus, a primary current of 3 amps results from a secondary load current of 360 amps.

Fuses take a long time to trip at their rating or they never blow. Thus, something well above 360 A on the secondary is needed to quickly blow the fuse. A 50 kVA transformer at full load would have a primary current of 50,000 / 14400 = 3.472 A. Likely the transformer is smaller than 50 kVA. The utility guys can give you better information on this.

A 50 kVA transformer with a 14,400 V primary probably has about a 100 A primary current when the full secondary is shorted, assuming about 3% transformer internal impedance. Again the the utility guys can give you better information.

.

 

[Iron_Ben]

You are trying to change something outside your jurisdiction. Not saying it is wrong to give them a piece of your mind, but your inspector title means little to them.

Agree with this above from Kwired.

We would rig up something like this every once a while. Never thrilled to do it, but it was SOP when a customer's direct buried underground service failed. Usually at 2:00 am. And a good example of why we have put everything below grade in pipe for 30+ years. So when one of the old direct buried services did fail, we'd run a temporary feed to the house on top of the ground in 2" PVC pipe, sch 40 or sch 80, whatever we could get our hands on. Then it would be a matter of calling One Call, waiting for the area to be marked, getting a job order drawn up, digging a trench and putting the new service in conduit. We expedited these jobs within reason. Sometimes the temporary fix would be in place for as little as a week, but 10 days to two weeks was probably a typical amount of time. Is it less than 100% safe? Yup. But in the real world, you have to balance the customer's desire for electric service against the safety issue. In the half dozen or dozen of these I was involved with over the years, we never had a safety issue or customer complaint. The goal was to get the lights back on as quickly as possible with a reasonably safe temporary fix, and then to get the permanent service reinstalled within a week or two.

 

[jakedoub]

Thank

Thank

Thank you all for the responses, it is greatly appreciated. Although the this installation is out of the scope of an "inspector", I am also involved with public safety and emergency management. I would have no issue with the installation if it was an actual emergency and was installed for a reasonable time. A month and a half to two months is not reasonable for an emergency. What I have been used to in the past, was for a situation like this where the expected date of repair was more than a week out, a contractor would install a temp pole with proper bracing etc. until the request order for repair was completed, boring equipment reserved, and job completed.

gar, thank you for posting the math. Would you or anyone else be able to correct my calculation or help clarify where I am mission information?
P = 3sqrt x 14 400v x 3amp
= 74 824.5949kva

I = 74 824.5949 / (3sqrt x 240)
= 180amps

Available secondary fault current is 180amps? I am more familiar with the traditional 480/277 delta to 208/120 wye transformers, which is why I'm reaching out for mathematical help on this one.


To be honest, what concerns me is that the utility company told me that they do this all of the time. This jurisdiction has a lot of foot traffic and a lot of families that are here and if this type of work is done all of the time, I really have a problem. I do not want us to be in the news. I appreciate everyone's professionalism and each of your responses.

 

[Iron_Ben]

You're getting three phase and single phase calculations confused. Transformer impedance is needed too. Also just because the primary is fused at 3 amps (which seems more speculated than confirmed) doesn't mean you multiply that by the applied primary voyage to get rated kva of transformer. Although it will get you in the ballpark.

Standard kva ratings of single phase padmounts are 25, 37.5, 50, 75.... Let's assume this one is a 50. Full load secondary current = 50,000 volt amps/240 volts = 208 amps. Now let's assume the impedance is 1.8%, which I know to be a reasonable guess (It's on the transformer nameplate if you must have it). 208 amps/.018 = 11,600 amps or so available for a bolted fault at the secondary terminals. Note that the dreaded square root of 3 wasn't used in this single phase calculation.

 

[jakedoub]

Thank you Iron_Ben

Thank you Iron_Ben

Thanks Ben, that certainly clarifies it. I appreciate you all taking the time to assist me actually understanding this. I forgot that I am dealing with single phase on the secondary, and yes, the sqrt3 is a dreaded number as shown in my miscalculation below.

 

[JRW 70]

Foundation in Law or Ordinace, etc.

Foundation in Law or Ordinace, etc.

(I'm sorry to go into law again
since I did so poorly in my law
schooling. My undergrad degree
is in Mechanical Engineering, and
that is how I tend to think in
regard to problems.)

You need to go through the state statutes
and any state controlled entities that can
make policy. See if you have the athourity
to declare it unsafe. If so, does your employer
have someone who could take action in
court ( district prosecutor, etc. ) the threat
of criminal or civil liabilities may be enough
to push them to be more pro-active in their
response time.

You need to know what tools legally you actually
have. And from what was said about the lack of
concern from everyone else, you will unfortunately
have to do the research yourself.

JR

 

[augie47]

I've spent a lot of my life "jousting at windmills" with little success.
Document your concerning to POCO, put the stomach ulcer medicine back on the shelf, be patient and remain available to testify as an expert witness when litigation day arrives.

 

[JRW 70]

I've spent a lot of my life "jousting at windmills" with little success.
Document your concerning to POCO, put the stomach ulcer medicine back on the shelf, be patient and remain available to testify as an expert witness when litigation day arrives.

This is perfectly said.

 

[Bugman1400]

What POCO is this? I have seen a lot of POCO distribution standards and have never seen this. If this is a permanent service and not just a temp feed for construction, I cannot figure why this service was not a simple UG service from the padmount to the house.

 

[junkhound]

Must be a temp bypass. e.g the mention of attached with duct tape...

Anyone who uses duct tape knows that in an outdoor environment it only lasts a few months (especially in sunny climes), then the conduit would fall off the trees.

 

[JoeStillman]

The only really unusual thing about this installation is the wiring method. No utility I know installs overcurrent protection on transformer secondaries. The NEC rules that we all follow are based on the assumption that the service overcurrent device is our first line of defense.

The wiring method could have been worse. I've seen messenger cable hung off the trees. At least there's some PVC conduit. It shouldn't be left that way though. In a hurricane area, you want all that stuff underground.

 

[jakedoub]

No action will be taken

No action will be taken

Thank you for all the input. I had to leave the area for a few days so I'm just getting back to responding. The utility company is Berkely Electric Cooperative, stationed out of Johns Island, SC.

I have gone as far as I can looking into the legal aspect, in regards to governmental oversight. Unfortunately for me, there is not oversight and the only agency who could get involved is the Office of Regulatory Staff. They informed me that there is nothing they are able to do since co-op's are self regulating and provide an elected managerial staff. I would like to have our Town's legal council pursue the issue, however my boss has told me to let it go. He took no action and when I asked him why, his response was for me to let it go because it takes time to reserve a boring machine. I would normally let something like this go if it was for a few days or a week even. However, it's going on 5 weeks.

I agree that utility companies do no put ocpd's on the secondary and that is where I'm trying to point out how large the available fault current is.

My last option will be to send a certified letter to the utility as a concerned member of the public, who has some electrical knowledge, and give them my input on the whole mess. If they use the NESC as a standard, I've combed through the book today with little areas that I could stretch for this to be acceptable.

Needless to say, I am upset at the lack of concern regarding safety from all parties involved. I do appreciate all of the responses here, you all have been a great help and I hope I will be able to contribute to other peoples questions in the future as well.

 

[kwired]

Thank you for all the input. I had to leave the area for a few days so I'm just getting back to responding. The utility company is Berkely Electric Cooperative, stationed out of Johns Island, SC.

I have gone as far as I can looking into the legal aspect, in regards to governmental oversight. Unfortunately for me, there is not oversight and the only agency who could get involved is the Office of Regulatory Staff. They informed me that there is nothing they are able to do since co-op's are self regulating and provide an elected managerial staff. I would like to have our Town's legal council pursue the issue, however my boss has told me to let it go. He took no action and when I asked him why, his response was for me to let it go because it takes time to reserve a boring machine. I would normally let something like this go if it was for a few days or a week even. However, it's going on 5 weeks.

I agree that utility companies do no put ocpd's on the secondary and that is where I'm trying to point out how large the available fault current is.

My last option will be to send a certified letter to the utility as a concerned member of the public, who has some electrical knowledge, and give them my input on the whole mess. If they use the NESC as a standard, I've combed through the book today with little areas that I could stretch for this to be acceptable.

Needless to say, I am upset at the lack of concern regarding safety from all parties involved. I do appreciate all of the responses here, you all have been a great help and I hope I will be able to contribute to other peoples questions in the future as well.

Don't send your letter to the line crew, send it to the business office, and include some "what if" scenarios describing possible electrocution and potential lawsuit as a result, and also give them reasonable cost effective and safer alternate solutions - even if it is intended to be temporary.

 

[ggunn]

...however my boss has told me to let it go. He took no action and when I asked him why, his response was for me to let it go because it takes time to reserve a boring machine. I would normally let something like this go if it was for a few days or a week even. However, it's going on 5 weeks.

I know this sounds cynical, but are you willing to risk your job over this?

 

[readydave8]

Be patient and you'll see worse