Ground and Neutral Wires
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Thanks for the comments. I have reached out to some local installers for help. Once I get their feedback I will post it here.Comment
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Not sure how that would be possible as there should be no upstream GFCI breakers. Only thing up stream should the Main Service Breaker. Even if it were a sub panel you would not feed it with a GFCI feeder as it would be operating constantly from false trips. Anyway I was just curious because there are no 120 volt loads I know of.Comment
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My guess is the neutral is for CPU monitoring. I once put in a 300KVA UPS system where the building supply was a 480v ungrounded delta. The UPS wanted 480Y with neutral. Upon investigation we found the UPS only used the neutral for metering and monitoring. So we used 250watt ground transformers to synthesize the neutral. Only drawback is the the UPS then had to feed a delta load but that was easy with the load side 480 to 208/120 distribution transformer.
I can see and understand a Ground or Zero Voltage reference, but a grounded circuit conductor provide no reference as it would vary with current. Only that makes makes any sense is for Control, but that requires the AC to be converted to DC which means either a transformer or SMPS. and it makes no difference if you use 240 or 120. Adding 120 just adds cost and complexity. I am sure there is a reason, but darn if I can put my finger on it. Nothing adds up.MSEE, PEComment
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I have CT's on both legs of my SolarEdge inverter's output, and whatever current it draws at night is equal on both. As far as I can tell, there is no 120 v load that uses the neutral conductor, so I can't offer any insight into why it is required.CS6P-260P/SE3000 - http://tiny.cc/ed5ozxComment
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No Single or Poly Phase Power Meter uses Neutral.MSEE, PEComment
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+1
By measuring current in all but one of the leads you know all of the currents, since they must sum to zero.
But the "true" measurement requires knowing all the line to line voltages in a system where the neutral is not used or all of the line to neutral voltages in a system where the neutral is used for some loads.
The commercial revenue grade meters instead assume that the neutral is midway between/among the lines and therefore they do not need any connection to the neutral at all.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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Huh? My meter measures and reports voltage referenced to neutral on both legs, and reports the power (and direction of current) on each leg individually. By measuring the current (and power) on both legs and finding them equal, I have sufficient data to see whether or not there are 120 v loads, right?CS6P-260P/SE3000 - http://tiny.cc/ed5ozxComment
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PT = P1 + P2
Poly Phase PT = P1 + P2 + P3.
Voltage in both is referenced to Ground, and current is CT. You could make an argument Neutral and Ground are the Same point in the meter cabinet or can because that is where N-G are bonded together. That is required by utility regulators so you do not pay for power loss between the transformer and you demarc. But at no point is Neutral current metered.
But a GTI uses your utility Transformer to derive the Neutral. A GTI is not capable of doing that. Got me stumped what they are doing. Gotta be a reason, but beats me for now.MSEE, PEComment
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Huh? My meter measures and reports voltage referenced to neutral on both legs, and reports the power (and direction of current) on each leg individually. By measuring the current on both legs (and finding them equal), I have sufficient data to see whether or not there are 120 v loads, right?
But the meter sockets for utility power meters of the residential and small commercial type do not even have a terminal jaw in the meter base to connect the neutral to the meter itself. So if you are using a revenue grade meter that is interchangeable with POCO meters, it will not use the neutral as a voltage
reference.
You can still tell if there are any unbalanced line to neutral loads without measuring either voltage or current at the neutral.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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Absolutely. No compromises there.
But the meter sockets for utility power meters of the residential and small commercial type do not even have a terminal jaw in the meter base to connect the neutral to the meter itself. So if you are using a revenue grade meter that is interchangeable with POCO meters, it will not use the neutral as a voltage
reference.
You can still tell if there are any unbalanced line to neutral loads without measuring either voltage or current at the neutral.
CS6P-260P/SE3000 - http://tiny.cc/ed5ozxComment
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Huh? My meter measures and reports voltage referenced to neutral on both legs, and reports the power (and direction of current) on each leg individually. By measuring the current on both legs (and finding them equal), I have sufficient data to see whether or not there are 120 v loads, right?
Utilities have bought many TV and Refrigerators doing that, and a few house fires.MSEE, PEComment
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No, the voltage is measured L1-N and L2-N. There is no ground reference provided. I just had another post go to moderation because I included the link, so just look up EKM Meter and you will see what I am using.
---Mod Note: Approved....CS6P-260P/SE3000 - http://tiny.cc/ed5ozxComment
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SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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