Is this a POCO problem?

[hillbilly1]

But they should never be bare aluminum underground, even a aluminum GEC is not allowed to be in contact with earth.

Do an experiment, take a section of bare aluminum conductor, bury it about a foot deep, then connect one end to your ground rod or service pipe, take another piece and just bury it and don't connect it to anything, bet the one connected to your service grounding dissolves much faster depending upon the neutral voltage drop., Yes I actually done this once, a long time ago, but it holds true. I did it to convince a person that a difference of potential will cause a conductor to dissolve where place in earth, this person was telling me that only DC will do this.

These are not bare aluminum conductors, that's why I think lightning probably punctured the insulation causing the deterioriation of the wire.

 

[hurk27]

These are not bare aluminum conductors, that's why I think lightning probably punctured the insulation causing the deterioriation of the wire.

No I agree that somehow these conductors had damaged insulation, I was just pointing out that once exposed the above is what happens, how they were damaged is anyones guess, as I have seen them get damaged when knifeing them into the ground (knife feeder not paying attention to feeding the knife allowing the cable to snag), rodents chewing on them, someone putting a tent stake in, and in one case the utility doing a direct bore beat the insulation with the spoon but it didn't break through the insulation at first, but a few years later the streatched or smashed insulation where it was hit just broke open and then the cable went bad, most likely because of the freezing and thawing of the ground up here, we knew this because we knew when the street lights were direct bored in, and the fact nothing happened in 10 years, then when we dug the cable up we found the beat marks the DB spoon left all along the cable, and the fact the street light feed was right there at the damage site, and then there is the lightning pin hole issue.

 

[kwired]

Wondered the same thing, but wasn't going to ask. I have never had a burned out neutral underground, normally the hot legs burning out. After all, it's 120 volts to "ground".

An interesting side note. We had a three phase open delta service that was CT metered at the pole that had been installed underground for many years. The owners noticed their bill was getting higher and higher until they decided to go with a single phase service. A few years later, (last year) we went back and had to extend the service for an addition. While we were digging, we found only three wires, not four. We dug around a bit and found the end of the fourth wire where it had been burning for 6-8 ft back in the ground. No wonder there demand and energy was so high... Fixed the wire just in case they wanted three phase back.

There is another "myth" as far as I am concerned. I don't know how many times someone thought they were losing power to "earth" through a bad underground conductor. I don't know what you had specifically in your described installation but at less than 600 volts not enough current will flow to earth to ever make any significant increase in metered power. If significant power does flow it is going to dry out the soil and then the resistance will increase and the amount of current will then drop. If aluminum conductors - forget it they will not last long enough to raise electric bill.

 

[hurk27]

There is another "myth" as far as I am concerned. I don't know how many times someone thought they were losing power to "earth" through a bad underground conductor. I don't know what you had specifically in your described installation but at less than 600 volts not enough current will flow to earth to ever make any significant increase in metered power. If significant power does flow it is going to dry out the soil and then the resistance will increase and the amount of current will then drop. If aluminum conductors - forget it they will not last long enough to raise electric bill.

I'm not so sure that you can call that a myth???

I have been on several high electric bill jobs that turned out to be exactly that an underground feeder or branch circuit that has bad insulation leaking to Earth, one was a old garage feed that after the garage had burned down no one ever disconnect the feed at the load side of the meter, while these were unprotected conductors as they were copper SEC that fed the garage the run was over 200 feet and it had burned in the ground about 150 feet of that distance, placing an amp probe on them confirmed that they were drawing over 180 amps 24/7 and in a month that is allot of KWH's the area had a high water table and it was a clay type soil, that was just one case where the owners bill was over $2k.

I had another at an old defunct camp ground that had been shut down for several years, the service that fed the camping sites was a 1200 amp MDP that had several sets of feeders that branched out through out the place, this service also fed a few out building the new owners wanted to get power to the out buildings so they had the service turned back on, after a month they got a $6500.00 bill and about freaked out, they called me to find the problem again all the feeders were copper and get this not even direct burial conductors, so over time the insulation had cracked and opened the conductors to earth, and with enough parallel paths to earth even with somewhat dry soil you can have allot of current flowing into earth.

even a simple UF going to a post light that I had found was pulling over 17 amps because of bad insulation and cause the electric bill of a friend of mines trailer to have his electric bill go from around $60.00 to over $200.00 it was on a twenty amp circuit and never tripped the breaker which also fed his shed, copper can last a long time underground when just about a foot of copper is exposed which like HV said will burn along its length if it is a long run. remember its not just going to Earth as you also have the neutral and EGC also ran close to the hot which can provide a much higher current as the distance between the conductors are not that far, true most of the time they usually end up tripping the breaker but not always and never in the case of a load side SECs coming from a meter or a high amperage feeder circuit.

How many bad underground circuit have you been called on that was tripping the breaker? now just think if they are close to the tripping point but don't trip the breaker, even a 15 amp circuit that has an underground fault that only pulls 14 amps can sit there and put 1680 watts on the electric meter every hour, 24 hours a day 7 days a week for 31 days, thats allot of KWH's

Keep in mind we are many times only called on the ones that do trip the breaker or because somthing stops working, if it trips the breaker its pulling allot of power and that is energy that we pay for.

 

[Hv&Lv]

There is another "myth" as far as I am concerned. I don't know how many times someone thought they were losing power to "earth" through a bad underground conductor. I don't know what you had specifically in your described installation but at less than 600 volts not enough current will flow to earth to ever make any significant increase in metered power. If significant power does flow it is going to dry out the soil and then the resistance will increase and the amount of current will then drop. If aluminum conductors - forget it they will not last long enough to raise electric bill.

Myth???

I guess basically what you have done is flat out call me a liar.:rant: If the ground is warm at the bad underground, there is current flowing, period. Do you not think it will ever rain and wet the ground again around the break? What part of burnt back 6-8 ft. didn't you understand? The aluminum conductors WILL continue to burn back as far as possible before the break is discovered. I really don't know what your experience is is underground breaks, but I have been finding and fixing them for about 25 years now. I know the distinctive smell, and can tell from the warmth of the ground when I get close. (After Dynatel puts me close). You keep your concerns. I know it will raise the power bill if it is on the right side of the metering device.

 

[hillbilly1]

I have actually seen this with 480 volt parking lot lights, lightning puncturing the insulation with the PVC conduit full of water which actually would boil from the current flow, eventually the wire burns up and the lights quit working, but the arcing continues to create heat and use kw's of power.

 

[kwired]

Wow I struck a couple of nerves. sorry I wasn't meaning to tell anyone they are liars. In cases where copper is used the conductor will survive, aluminum will not. There is a lot of aluminum underground around here and my experience and bias of the so called myth is mostly because of aluminum. I have fixed plenty of aluminum over past 25 years. Most copper I ever fix is damaged by someone excavating and is not just something that seems to fail for no real obvious reason if you don't look very hard. Aluminum is destroyed enough that those small clues are destroyed also.

Warmth in the soil? If you are feeling/ sensing it at the surface you have a pretty good circuit established - maybe even involving more than 600 volts, and you definately have copper conductors. Aluminum will not last long enough and if you have proper cover requirements that is a lot of heat to migrate that far to be able to feel it yourself, detect with sensitive instruments I can understand.

How often is the POCO transformer going to be able to supply 180 amps indefinately without tripping something, outside of commercial and industrial services and a few other exceptional services? Typical 200 amp single phase service on its own transformer often only has 25kVA - maybe 37.5 kVA if there is expected to be heavier loading. Transformers supplying more than one service are sometimes larger - if the load is actually there to need a larger transformer and is more likely to be possible there.

I might have said the wrong thing as a general statement- but if we are talking aluminum conductors I find it unlikely you are going to leak enough current to earth before the conductor itself develops a high resistance that you will make a very significant increase on someones power bill.

If you apply 120 volts directly to a 10 ohm ground rod you only have 1.2 kW of load. 28.8 kW per day With outrageous high electric rates that is still less than $5.00 a day.

Not saying some of the mentioned things can't happen but they are not the kind of thing that happens frequently, and with aluminum are almost impossible as far as I am concerned. Worst case I ever had was not exactly a current to ground leak it was a well pit filled with water because of a plumbing leak in the pit - pressure switch (which was in the pit full of water) would not open and well pump ran continuously - after a month I'm sure the well drew more power than what leaked to ground. Customer only called because of high electric bill that month.

 

[Hv&Lv]

Warmth in the soil? If you are feeling/ sensing it at the surface you have a pretty good circuit established - maybe even involving more than 600 volts, and you definately have copper conductors. Aluminum will not last long enough and if you have proper cover requirements that is a lot of heat to migrate that far to be able to feel it yourself, detect with sensitive instruments I can understand.

Where was it stated it was felt at the surface? It can be felt in an area about a foot around the bad underground. It is all aluminum conductors, mostly 4/0. I know what the voltage is that I work on, it is a 120 volt line. Do you know what a Dynatel is?

How often is the POCO transformer going to be able to supply 180 amps indefinately without tripping something, outside of commercial and industrial services and a few other exceptional services? Typical 200 amp single phase service on its own transformer often only has 25kVA - maybe 37.5 kVA if there is expected to be heavier loading. Transformers supplying more than one service are sometimes larger - if the load is actually there to need a larger transformer and is more likely to be possible there.

Who said the transformer has to supply 180 amps indefinately? An 8 amp load will increase the energy bill 70 dollars.

I might have said the wrong thing as a general statement- but if we are talking aluminum conductors I find it unlikely you are going to leak enough current to earth before the conductor itself develops a high resistance that you will make a very significant increase on someones power bill..

You can find it however you like, it is a fact. install a piece of 4/0 into a 200 amp breaker, bury the cut end 2' in the ground, and turn the breaker on. you will see for yourself.

If you apply 120 volts directly to a 10 ohm ground rod you only have 1.2 kW of load. 28.8 kW per day With outrageous high electric rates that is still less than $5.00 a day. .

By your own numbers that is $150.00 a month increase in energy cost. You don't think that is a substantial increase?

Not saying some of the mentioned things can't happen but they are not the kind of thing that happens frequently, and with aluminum are almost impossible as far as I am concerned. Worst case I ever had was not exactly a current to ground leak it was a well pit filled with water because of a plumbing leak in the pit - pressure switch (which was in the pit full of water) would not open and well pump ran continuously - after a month I'm sure the well drew more power than what leaked to ground. Customer only called because of high electric bill that month.

POCO's deal with bad aluminum underground wires as a part of doing business. It has to be included in the line losses for the utility, why wouldn't it be important?

 

[kwired]

Hv & LV, what kind of soil do you encounter the most when you have to repair these underground problems?

That could make some difference as to why you see things differently than me.

Most of what I have seen is usually in sandy soil. The wire has already disintegrated at the point of the fault - usually is not a very big section of conductor at all that burns up just a few inches most of the time, but is definitely no longer a complete low resistance path. By the time I am called to find out what is wrong there is no significant amount of current flowing - nothing is warm the dirt near where it was heated up is all dried out. Sure it will rain someday, but we don't have a funnel to divert water right to where this problem was so it remains fairly dry unless we have had exceptionally wet conditions.

It has been mentioned many many times on this forum that earth is not a good equipment grounding conductor. Less than 25 ohms is considered good enough for a ground rod. That would only be about 5 amps of current flowing through a 25 ohm ground rod at 120 volts. You think we are going to get anything significantly less in resistance than that from a short section of bared aluminum, then add to that it will get even higher in resistance as it turns into aluminum oxide? Heavy soils with less oxygen in them may allow for more current and more destruction, that or you have better electricity than we have

I have about as many years experience as you from what you said with locating underground faults, you probably have also located faults in over 600 volt stuff since that is part of what you do but I have not done that. I have never used Dynatel but do own a Rycom unit and have used similar Rycom with a previous employer. Never had a fault we could not find. Have dug a few holes that were not successful at finding what we were looking for a time or two, you learn from those mistakes. Really dry sandy soil - especially in a year like we are now having - you have to water the suspect area or you do not get good enough fault return current to find the fault easily, you can be second guessing everything you see for hours, put sprinkler on for a few hours and come back and you find the right spot within minutes.

 

[Hv&Lv]

Hv & LV, what kind of soil do you encounter the most when you have to repair these underground problems?

That could make some difference as to why you see things differently than me.

Changes from red clay to clay sand mix to all sand across our service territory.

Most of what I have seen is usually in sandy soil. The wire has already disintegrated at the point of the fault - usually is not a very big section of conductor at all that burns up just a few inches most of the time, but is definitely no longer a complete low resistance path. By the time I am called to find out what is wrong there is no significant amount of current flowing - nothing is warm the dirt near where it was heated up is all dried out. Sure it will rain someday, but we don't have a funnel to divert water right to where this problem was so it remains fairly dry unless we have had exceptionally wet conditions.

The church I was refering to in my original post had a higher than normal demand and increase in energy consumption that could not be explained. After about 4-5 months of this, they decided to do away with the three phase service. The high leg(appx.210-218V) was taken off at the vault when the church decided to switch to single phase service. The second pot wasn't removed for another couple of years because it was assumed they would want to go back to three phase. I understand why you would doubt that it will cause an increase in energy consumption being in sandy soil. The part I took offense to was the "tone" of your post, and the suggestion that I was lying.

It has been mentioned many many times on this forum that earth is not a good equipment grounding conductor. Less than 25 ohms is considered good enough for a ground rod. That would only be about 5 amps of current flowing through a 25 ohm ground rod at 120 volts. You think we are going to get anything significantly less in resistance than that from a short section of bared aluminum, then add to that it will get even higher in resistance as it turns into aluminum oxide? Heavy soils with less oxygen in them may allow for more current and more destruction, that or you have better electricity than we have

Here again, you are inferring I am making the whole thing up. We aren't discussing equipment grounding . I know the math, and the requirements. You don't have to be such a pedant. Smiley or not, that last part wasn't needed, and shows a lack of maturity.

I have about as many years experience as you from what you said with locating underground faults, you probably have also located faults in over 600 volt stuff since that is part of what you do but I have not done that. I have never used Dynatel but do own a Rycom unit and have used similar Rycom with a previous employer. Never had a fault we could not find. Have dug a few holes that were not successful at finding what we were looking for a time or two, you learn from those mistakes. Really dry sandy soil - especially in a year like we are now having - you have to water the suspect area or you do not get good enough fault return current to find the fault easily, you can be second guessing everything you see for hours, put sprinkler on for a few hours and come back and you find the right spot within minutes.

We have to do the same thing in our sandy areas.

 

[kwired]

You can find it however you like, it is a fact. install a piece of 4/0 into a 200 amp breaker, bury the cut end 2' in the ground, and turn the breaker on. you will see for yourself.

I will be doing that sometime next few days and will let you know what results were.

You want just the cross sectional area exposed 2 feet deep or you want 2 feet of bare conductor in the earth or try both ways?

I even have some mechanical watthour meters I can meter with that came from a POCO that upgraded to digital meters. It will not be on 200 amp breaker, it will be on 15 or 20 amp breaker, supplied by 14 or 12 AWG copper extension cord.

My guess is it will never draw enough current to trip the breaker, and probably will not even draw enough to blow a 5 amp fuse. Don't really want to leave it where someone will possibly get hurt but may leave it connected overnight just to see what results are on meter in morning. (I am out in country and am not too worried about someone coming along overnight and getting involved with it, if someone does I probably stopped a thief, or at least someone that should never be there, during the day I have family, friends that may be a problem and will not leave it during the day if I am not there)

 

[Hv&Lv]

I will be doing that sometime next few days and will let you know what results were.

You want just the cross sectional area exposed 2 feet deep or you want 2 feet of bare conductor in the earth or try both ways?

I even have some mechanical watthour meters I can meter with that came from a POCO that upgraded to digital meters. It will not be on 200 amp breaker, it will be on 15 or 20 amp breaker, supplied by 14 or 12 AWG copper extension cord.

My guess is it will never draw enough current to trip the breaker, and probably will not even draw enough to blow a 5 amp fuse. Don't really want to leave it where someone will possibly get hurt but may leave it connected overnight just to see what results are on meter in morning. (I am out in country and am not too worried about someone coming along overnight and getting involved with it, if someone does I probably stopped a thief, or at least someone that should never be there, during the day I have family, friends that may be a problem and will not leave it during the day if I am not there)

Either way. What you will be making is called a "worm getter" http://www.cpsc.gov/cpscpub/prerel/prhtml93/93075.html

 

[kwired]

Either way. What you will be making is called a "worm getter" http://www.cpsc.gov/cpscpub/prerel/prhtml93/93075.html

Didn't know someone actually sold those through bigger retailers. All the ones I have ever seen were made in someone's hobby shop. They don't work out so well with GFCI protection though. Not many good fishing worms to get here in the sand.

 

[Electric-Light]

I didn't read the long posts... but if you drive in an aluminum rod into the ground and connect it to anything else that's in the ground, it will start dissolving because, the soil contains mineral and you basically created a shorted battery.

 

[kwired]

I didn't read the long posts... but if you drive in an aluminum rod into the ground and connect it to anything else that's in the ground, it will start dissolving because, the soil contains mineral and you basically created a shorted battery.

That is not being debated so much as if connected to AC source how much current will flow to ground, and once the aluminum is oxidized will there be enough heat to continue to burn away insulation and allow the aluminum to continue to conduct at a high enough current to keep going until a large amount of conductor essentially is consumed and at same time significantly increasing the electric bill for the user.

I have not had chance to do my experiment yet but I say it will not use a very significant amount of energy as far as cost of electric bill is concerned, and likely will not damage much area of the conductor without something happening to expose more conductor like burning away insulation to expose more conductor. Direct buried conductors have thick enough insulation I don't think it will burn enough away to cause much trouble unless helped by lightning maybe.