What a nice wave

Kingrex

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My parents have 137 acre. People have land around here. They have their own transformer. They have a very nice sine wave. Oddly, the THD is 2.7%. Not much different from most other homes I'm in. I sort of wonder how much distortion is from the utility transformer itself. I would not think much. Their neighbors are not industrial farmers. Its cattle country. Mostly land and cows.
 

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howiebrou

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My parents have 137 acre. People have land around here. They have their own transformer. They have a very nice sine wave. Oddly, the THD is 2.7%. Not much different from most other homes I'm in. I sort of wonder how much distortion is from the utility transformer itself. I would not think much. Their neighbors are not industrial farmers. Its cattle country. Mostly land and cows.
Some cow pictures would be appreciated.
 
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Kingrex

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They are the retired executive type. He use to keep 10 cow so it was a farm and received the tax break. Now its just hayed. Mom is furious hes going to spend $800 to fix an old outdoor barn cats teath.
 

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Alrainbow

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here is a pic of my transformer replaced a few weeks back , of my home down south NC . oddly the input is single phase to to neutral . input i think is 12k or so . the overhead feeds in my rural area are not 3 wires as most are . there 4 wire starr i cant recall ever seeing this before . it comes down off a wooden utiluity pole ona road outside my private developemnt . crazy high voltage here just one wire insulated and the second is bare copper lol . stays under ground into my transfomer pad . secondary is 120/240 volts REX any thoughts on this type of distrabution ? its not a test i tryly have no idea what they are doing never seen this anywhere before my place . at one time a few years back it was older system just 2 wires on older poles going back and forth on my road to my place . now since they have built many homes outside of my area they beefed things up , they have a huge transfomer staion a few miles down the road from me . but still for me and others around just the 4 wires alone .


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Kingrex

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I don't know about medium voltage 4 wires vs 3 on the power poles. I always thought they ran a single 12480 into the transformer and got the split 120/240 with a neutral. All the pole mount around me are a single wire with a single fuse. If you look, you will notice all the transformer cans have a ground lug and a solid #2 will come down the side into the earth. Thats all I have observed.

Any of the towers I did, the utility vault equipment and work was done by the utility. We put a pipe between the 2 and pulled wire. Thats it. They terminate the medium voltage, we terminate the low voltage.

I call 600v and below low. I don't know the break between medium and high. Usually a power pole in a neighborhood is 12,480V. Could be 24,000 V. The big wires on towers can easily be 300,000V. Probably DC at those high voltages.
 
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Alrainbow

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Ty from math backing into high voltage of tranny it’s 12k about
they could have used 25k but choose not to. The tranny has two taps on input. Like you just a pipe up a pole and can’t have a tranny on that pole. I have seen both typs single and 3 phase it seems to depend on kva size. But never seen 4 wire star. it’s only .4 amps at 12k input
I’ll ask a utility truck down there soon. All I can think of is makes no sense in a lower voltage.
ty for Your thoughts
 

Kingrex

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Are you sure its a 4 wire star. Each phase 90*? I have never heard of such. I can not find anything online.

Let me know what you find out.
 

spiritofmusic

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Alrainbow

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Are you sure its a 4 wire star. Each phase 90*? I have never heard of such. I can not find anything online.

Let me know what you find out.
Im very sure it’s not two two phase no way
it has 4 wires and one goes uninsured into the conduit down the pole.
i never seen this makes no sense to me. There is only one insulated conductor in the downward pipe
I’ll show a pic
many times metal poles have 4 wires one being a ground conductor to keep metal poles at same potential There wood
 

Kingrex

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Is it a ground? I assume the pipe is rigid steel for physical protection. They need to bond the pipe to keep it from being a choke.

My ground resistance meter is a clamp on device. The general way it functions is it looks at the utility side of the wire and the earth side of the wire. It injects a current. It does a calculation with the assumption that the utility side resistance is 0 ohms as all the grounds through all the poles added together gets to 0 ohms.

I figured this was derived on the low voltage side with a bonded neutral across many poles and many transformers. Maybe you live so far out, they carry the ground with the high voltage wires?????

I will look at my folks tomorrow. All I remember about theirs was the fuse seemed tiny. Like a pencil.
 

Alrainbow

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It’s not a ground and poles are wooden. Only two conductors go into a pvc pipe on the side of the pole
one is very thick insulated
the second is bare copper looks like 4 gauge
thats it.
also there is no ground system as it’s high voltage. They might bond the neutral inside the transformer but I’m not sure was not there at replacement
I’ll be back there this week I plan to stop by utility yard a few miles to ask. I’m curious for sure
 

Kingrex

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So I looked at my parents today. I actually watched the wire on and off for a few miles on a drive today. There is definatly a ground running parallel under the phase wire.

At the pole mount transformer at their house, you can see the parallel ground drop a tap to the transformer can, then continue down the pole and into the earth.

It would only make sense on an underground feed to a vault that they would need to bring this ground down through the pvc along with the phase wire to bond to the transformer in the vault.

This was only a single wire run. I still need to look at some larger 3 wire runs. If they were to drop 2 hots to the vault I could see how a ground would not be necessary. But maybe in your location they are running a lot more current from location to location and are apping off small loads along the way. So maybe they ran a ground with the phases to allow usage of a more available residential transformer that takes a single hot and ground.
 

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Kingrex

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Here is the neighbors cows. They were at our driveway. That my family Crest from England.
 

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Kingrex

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I looked at some other runs of higher power on towers today. There are the 3 phases, and there is also 1 to 2 additional wires that ride on the top of the towers bonding it all together.
 

Alrainbow

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ill be down south soon to share pics . if its a ground then its also a neutral as there is only one conductor that's shielded going down the pole . as it is only .4 amps it may not matter meaning the current is so low its ok on voltage drop . i agree most poles metal ones to have a continues continuity wire . each pole that has a trany always has a ground to a ground rod but this is not done on poles that have no tranys .
 

Kingrex

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Let me clarify, I am not a lineman in any way shape or form. I am an 01 which is 600 volt and below commercial.

This is more what I think I see. See the image from Mike Holts website. The utility neutral is bonded to make a ground fault path to blow the fuse in a phase to ground fault. In the image Holt don't show the incoming utility wire very clear, but I see the ground/neutral bonded on the primary and secondary via the green dots. Look at the transformer in the image. Its a single black phase on top, and the return bottom has a green dot. Thats ground.

At my parents drop and other rural drops, a neutral/ground wire clearly travels with the phase on the poles. They don't have low voltage wires running those distances to carry the neutral/ground with the low voltage.
I was looking at much larger utility wires yesterday and they had 2 wires on top of the towers that ran unbroken with the insulated phase conductors. They even had a jumper going to a support cable in the earth.

At my home in Seattle, there is only 1 medium voltage wire on top of the pole, but I believe the load side low voltage is where they are maintaining the neutral/ground bond that goes back to the utility substation bonding the medium and low voltage together. So in a phase to ground fault say between your service mast and utiltiy wire, the fault would have to run many miles to a substation to loop back and blow the fuse on the pole mounted transformer.

This is a bit of an assumption. But I base it on I am very confident its AC on the medium voltage wire on the top of the pole at my Seattle home. AC has to have a return path. It can not work without it. From what I know, they only run DC on very high voltage transmissions lines up in the hundreds of thousands of volts going hundreds to thousands of miles.

They therefore then have to use the low voltage neutral/ground as a common neutral/ground with the medium voltage in urban environments. Since we are so dense, its less wire to do this in an urban setting. Therefore we don't see a second, or in your case, 4th wire with the medium voltage.

Thats my take. Where is a lineman. Don't we have one on this forum. 20220201_112529.jpg
 

Kingrex

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The above image by Holt also clearly shows why an isolation transformer does not rid ground loops. Its all bonded together.
 

Alrainbow

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Exactly Rex it’s why I said it’s a neutral not a ground or tower bonding. at each change of voltage we must bond a ground to become that neutral.
So an example is
277/480 to 120/208 the secondary must be 4 wires in 3 phase system
its considered a new service
so at any untililty trany it’s the same but the utililty company does have to be ruled by NEC code. as the wires go pole to pole they are not bonded on line side but must be on load side. of the trany has a neutral on line side it gets bonded to ground. So if the utility is not using single phase then it’s a neutral
and Rex while I was certified for above 600 volts it’s many years ago
and I feel you have more new experinece ok. im not in anyway testing you i mean this.
im just being curios is all.
 

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