 tschmidtPremium,MVM
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Milford, NH
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Re: Electrical Insanity said by Zapppp :In this case, the ground and neutral are connected within the premises, so the current will flow through the ground wire to the ground rod and/or water pipes. I live in a rural area - no water pipes for me. Even with town water plastic is rapidly replacing lead and copper piping. Which is why the NEC now requires a ground electrode even on town water.
said by Zapppp : Look at the pole transformers. They don't have a neutral on the primary side. I don't know where you live but that is certainly not the case here. Most utilities use MGN, multiple grounded neutral. Neutral current flows in both the physical neutral conductor and Earth.
The neutral conductor is sized so almost all neutral current flows through it, Earthing is used primarily for lightning protection.
/tom |
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OK, where's the neutral on the primary side? |
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sk1939Premium
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Washington, DC
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| Right in the middle. |
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| But there's no primary neutral wire. The primary is connected between the primary hot and ground. The secondary neutral is also grounded. |
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sk1939Premium
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Washington, DC
kudos:9 | That may be, but it is still necessary. |
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tschmidtPremium,MVM
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Milford, NH
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1 edit | reply to Zapppp
MGN Residiental |
said by Zapppp :OK, where's the neutral on the primary side?
Here you go
There are two types of distribution systems. Most parts of the county use MultiGrounded Neutral (MGN). The transformer only has one high voltage insulator. Primary Neutral is bonded to the centertap of the secondary and in turn bonded to ground electrode at the pole and ultimately at the meter/service disconenct of each customer.
/tom |
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| reply to Zapppp
said by Zapppp :But there's no primary neutral wire. The primary is connected between the primary hot and ground. The secondary neutral is also grounded.
In some secondaries there is a neutral (grounded one, but still). If you insist on proper wording, replace "tree branch takes out service neutral (but not hot)" with "tree branch takes out service return wire". |
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tschmidtPremium,MVM
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| reply to sk1939
said by sk1939:Right in the middle.
The pictures you posted are a little confusing as they show two different primary arrangements.
The one one the left is MGN like the picture anon Zapppp posted. Even though in my post calls out an external jumper that really is not the case, primary of connected to secondary within the transformer.
The one on the right has two high voltage bushings because neither primary is at ground potential. |
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 49528867Premium
join:2010-04-16
Fort Lauderdale, FL
kudos:3 | reply to Zapppp
said by Zapppp :But there's no primary neutral wire. The primary is connected between the primary hot and ground. The secondary neutral is also grounded.
There most certainly is, as the normal way to connect a dual busing transformer in a multi-grounded neutral (MGN) system is to run a conductor from the neutral primary bushing to the MGN that conductor will also be bonded to the poles ground.
Note carefully in the shot above and you can see the conductor leaving the primary neutral bushing on the left of the lid, it then travels to the pole and can be seen just below the lid and the upper bracket and from there it travels down and is connected to the MGN.
Now in the upper shot above you can see the secondary bushing is bonded to the transformer case and on the upper right is the primary neutral bushing though you cannot see the conductor going toward the rear of the transformer, in the lower shot you can see the conductor from the primary neutral bushing of the same transformer is connected to the MGN and is “C” crimped to the pole ground, as is the transformer case.
Wayne
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"It is sobering to reflect that one of the best ways to get yourself a reputation as a dangerous citizen these days is to go about repeating the very phrases which our founding fathers used in the struggle for independence." - Charles A. Beard |
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| reply to tschmidt
said by tschmidt:Most parts of the county use MultiGrounded Neutral (MGN). The transformer only has one high voltage insulator. Primary Neutral is bonded to the centertap of the secondary and in turn bonded to ground electrode at the pole and ultimately at the meter/service disconenct of each customer.
So in this case, an open neutral on the utility side will not cause problems because there's also a return path via the ground connection. |
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tschmidtPremium,MVM
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| said by Zapppp :will not cause problems because there's also a return path via the ground connection. Not sure exactly what you mean.
There may or there may or may not be a low impedance path. Even in the case where there is one it is unintentional and results in a safety hazard.
/tom |
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