Electricity wants to go to ground?
- Thread starter zappy
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Ok. Is that ground reference from two ground rods?
What does that mean? what does it matter? The grounding connection has nothing to do with the current flow through loads.
there is 120 volts between each end of the transformer secondary winding and the center tap... and there is 240 v between the ends of the secondary winding. Loads connected to the center tap and the winding end will have 120v potential and the current will flow between the center tap through the load to the end of the winding ( and the other direction too ...alternating current)
There is no real reason you could not ground either end of the transformer winding and then that conductor would be at the same potential as the ground and the center tap would then be 120v to ground and the other end of the winding would be 240 v to ground ... grounding the center tap assures there is no voltage higher than 120 volts above the ground we are standing on that we could touch. Course if we really tried we could touch both phases .
So a 40 amp load on one leg and a 10 amp load on the opposing leg wouldn't create any problems.
no. what problems would it create?
With a difference in resistance there will be a difference in voltage. How would you keep the 120 volts steady?
why don't you explain what that has to do with the subject of the thread, or your assertions during the course of the thread?
I'm goin to bed...
good night
- Occupation
- Licensed Electrician
Only if you lost your neutral connection.
His whole point is that there doesn't need to be a neutral.
why don't you explain what that has to do with the subject of the thread, or your assertions during the course of the thread?
I'm goin to bed...
good night
Very well. I have already addressed the OP. breakers trip and the neutral is needed for safety on a distribution line by being multigrounded. It is also meant to be a low resistance path for imbalance currents to return to source. Your posts brought us off the main topic and to this point.
Sleep well...
- Location
- Illinois
- Occupation
- retired electrician
The source of the unbalanced currents on the secondary side of a transformer is the secondary side of that transformer. There is no need for a grounded conductor on the supply side, but if you want one, use a grounded wye to supply the transformer, but supply it line to line and not line to neutral. The issue of stray voltage is the voltage drop on the primary grounded conductor. If you don't use that conductor as a current carrying conductor that issue goes away.
- Location
- Illinois
- Occupation
- retired electrician
No, there would be no issues, but there would be 30 amps on the secondary neutral. That has nothing to do with a primary neutral or lack there of.
- Occupation
- Licensed Electrician
No, he is saying that you do not need to ground the neutral. You can have an ungrounded secondary and it will function fine, it just won't trip any breakers on the first fault. You can ground one side of the secondary and the voltage to neutral will stay the same.
kwired
Electron manager
- Location
- NE Nebraska
Neutral and Ground are not the same thing, doesn't matter if we are talking multiple Kvolts or 120/240.
A neutral is a conductor that is common and at equal potential to other system conductors, and only carries unbalanced current from other conductors. Like the center tap on a single winding or the common point of wye connected windings.
Delta transformers do not have a neutral conductor. A delta system with a grounded mid point on one phase may sometimes refer to this point as a neutral, and it is a neutral to the two phases adjacent to it but is not neutral to the entire delta bank.
You can ground any conductor of any system. If the system has a neutral conductor it is usually the preferred conductor to be grounded.
600 volt and below we only ground neutrals (if we have a neutral) at the transformer and at service equipment. Beyond that we separate neutral from equipment grounding conductors to prevent objectionable current on non current carrying metal objects.
Utility systems with grounded neutals and grounding occuring at almost every structure creates multiple pathways from the conductor to earth and all of those paths will conduct some current. The bulk of the current will flow through the intended conductors. Develop just a little resistance in a connection and some more of it will flow through all the unintended paths. Voltage drop is a natural occurance in any conductor. Bring two objects near each other that are connected to different points along the utility neutral but not directly to each other and this voltage drop will be measured between the two. This is the source of many stray voltage problems. It is not really stray voltage, especially if it is determined what the cause of the voltage is, but many call it stray voltage anyway.
Will loads work with or without a neutral or ground?
A load is only looking for its designed voltage in order to operate as designed. It will not care if a particular conductor is grounded or not, as long as proper voltage exists between all conductors of the circuit the load will work fine.
A neutral is a conductor that is common and at equal potential to other system conductors, and only carries unbalanced current from other conductors. Like the center tap on a single winding or the common point of wye connected windings.
Delta transformers do not have a neutral conductor. A delta system with a grounded mid point on one phase may sometimes refer to this point as a neutral, and it is a neutral to the two phases adjacent to it but is not neutral to the entire delta bank.
You can ground any conductor of any system. If the system has a neutral conductor it is usually the preferred conductor to be grounded.
600 volt and below we only ground neutrals (if we have a neutral) at the transformer and at service equipment. Beyond that we separate neutral from equipment grounding conductors to prevent objectionable current on non current carrying metal objects.
Utility systems with grounded neutals and grounding occuring at almost every structure creates multiple pathways from the conductor to earth and all of those paths will conduct some current. The bulk of the current will flow through the intended conductors. Develop just a little resistance in a connection and some more of it will flow through all the unintended paths. Voltage drop is a natural occurance in any conductor. Bring two objects near each other that are connected to different points along the utility neutral but not directly to each other and this voltage drop will be measured between the two. This is the source of many stray voltage problems. It is not really stray voltage, especially if it is determined what the cause of the voltage is, but many call it stray voltage anyway.
Will loads work with or without a neutral or ground?
A load is only looking for its designed voltage in order to operate as designed. It will not care if a particular conductor is grounded or not, as long as proper voltage exists between all conductors of the circuit the load will work fine.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Deltas are still grounded to Earth but not in the sense that a Wye is.
To provide for lightning protection and to diminish the build up of static charges they use a simple transformer called a zig zag that has a center tap but no secondaries, it keeps the delta voltages in check with a reference to Earth, but this does not cause normal current to flow into the Earth like the MGN of a Wye system.
To provide for lightning protection and to diminish the build up of static charges they use a simple transformer called a zig zag that has a center tap but no secondaries, it keeps the delta voltages in check with a reference to Earth, but this does not cause normal current to flow into the Earth like the MGN of a Wye system.
kwired
Electron manager
- Location
- NE Nebraska
How frequently are they installed along the line, or are they just at the ends of the line?
I have seen miles of transmission lines that I assume are from delta secondaries and you never see any kind of transformer except at the substations. Newer lines have the shield conductor at top of poles but some older lines just have the three phase conductors and that is it. No electrode conductor attached to any of them, so none of them is likely to be grounded.
The "primary neutral" you are refering to is little more than a secondary neutral of the upstream system. A substation transformer is just that, a transformer.
You are correct. The "static shield" at the top of the towers are more for lightning protection and to provide a low Z path in case one line falls or a tree lays on one. They are connected to the pole (tower) and to ground rods at the poles(towers). they are not considered a neutral.
Utility lines are nothing more than secondary lines of a larger system. Most substation transformers are delta-wye transformers, 10-20 mVa.
- Location
- Illinois
- Occupation
- retired electrician
What does that have to do with the unbalanced current on the secondary side of a transformer that feeds a building?
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