bobby ocampo
Senior Member
What is the importance of connecting the neutral to the earth or ground?
Neutral Connection in a System Grounding
- Thread starter bobby ocampo
- Start date
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- Location
- Massachusetts
bobby ocampo said:
IMO in regards to premises wiring systems operating under 600 volts the connection of neutral to dirt is of much less importance then the connection of neutral to the equipment grounding conductor.
And of course I should make clear my post are only aimed at solidly grounded systems.
bobby ocampo
Senior Member
Isn't it that if neutral is not connected to ground it is considered ungrounded system? If connection to neutral is of LESS IMPORTANCE then why do we have a SOLIDLY GROUNDED SYSTEM?iwire said:
bobby ocampo
Senior Member
And if neutral is not connected to ground then we should use a two pole circuit breaker because neutral will be ungrounded current carrying conductor?
peter d
Senior Member
- Location
- New England
bobby ocampo said:
Which connection is more important in your mind? A connection to earth of an unknown impedance? Or a connection back to the source via a metal conductor (bonding jumper)? Which will facilitate the quick operation of an OCPD?
- Location
- Massachusetts
bobby ocampo said:
Ahhh, now I think I see the issue.
We are not using the term 'solidly grounded' in the same way and I don;t know which one of us is using that term correctly.
To me the solidly grounded means a solid connection between a line conductor and the equipment grounding conductor. The term solidly grounded does not refer directly to the connection to the earth.
You have been working on substations which I imagine use a multi-ground neutral which is different from premises wiring which use separate grounding and grounded conductors.
- Location
- Massachusetts
Here is a picture of what I work with.
To me what makes this solidly grounded is the direct low impedance connection of the "Equipment Grounding Conductor" to "Neutral"
To me what makes this solidly grounded is the direct low impedance connection of the "Equipment Grounding Conductor" to "Neutral"
peter d
Senior Member
- Location
- New England
iwire said:
That is true, and the MGN is far more important to be grounded/earthed because it has the potential to be energized at primary voltage.
- Location
- Illinois
- Occupation
- retired electrician
Solidly grounded just means that one of the circuit conductors is connected to earth without any intentional resistance or impedance. As far as calling the system a "grounded system" the connection to earth is very important. As far as the importance of the connection to earth for system operation and safety on under 600 volt systems, it is not as important as the system bonding connections.
- Location
- Massachusetts
don_resqcapt19 said:
OK then it was I who was using that term wrong.
That just strikes me odd as the difference between a grounded system and a ungrounded system is not the grounding electrode system but the lack of a bonding jumper.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Additionally, a floating supply system (i.e., ungrounded) will typically show the same voltages to earth as a grounded system with a high-impedance voltmeter due to capacitive coupling with the earth and nearby grounded surfaces.bobby ocampo said:
However, that coupling is of very high impedance, rendering that coupling weak and unstable. Nearby high-voltage sources could raise that voltage to very high levels, not to mention an accidental primary-to-secondary contact.
The relative voltages between conductors would remain the same, but a high voltage contact could render one service line conductor at, say, 15kv to earth, one at 15,120v, and the third at 15,240v. That would be disastrous.
By the way, they have 240v in many European and other countries, but many of them don't have a grounded center-tap. Instead, one end of the 240v supply is grounded. So they have 240v and 0v, not 120v, 0v, and 120v.
By solidly grounding one circuit conductor, we fix the voltages on the other conductors to earth to predictable and designed-for voltages. I typed up a little ditty a while back that may help explain grounded neutrals a bit:
http://forums.mikeholt.com/showpost.php?p=708650&postcount=4
bobby ocampo
Senior Member
peter d said:
Both are important. It is still important to connect the bonded EGC to ground. Never will I say that bonding is not important. What I will always say is it is important to connect the bonded EGC to ground or earth.
bobby ocampo
Senior Member
roger said:
Can you site specific provision of the 2008 NEC where it is now require to use two-pole circuit breaker for line to neutral load if the neutral is grounded?
bobby ocampo
Senior Member
iwire said:
Definition of Solidly Grounded in accordance with IEEE/ANSI STD 142
solidly grounded: Connected directly through an adequate ground connection in which no impedance has been intentionally inserted.
bobby ocampo said:
imo the importance of earthing the neutral is to provide the utility with a return path in the event of a bolted fault before the main. (of course, if the utility wasn't so cheap, providing a separate grounding conductor would alleviate using the earth and probably save lives as well, since the earth path is not so hot)
bobby ocampo
Senior Member
don_resqcapt19 said:
Why is it important in System Grounding?
What is the importance of grounding or connecting to earth of the neutral of the transformer? Or in premises wiring connecting and bonding the neutral and grounding in the service equipment?
don_resqcapt19 said:
Do you mean that it will only be important if voltage is above 600 volts?
LarryFine said:
Here is an interactive example of what Larry typed. (note; some browsers may not work correctly with the switches)
http://home.comcast.net/%7Eronaldrc/wsb/ax.htm
Roger
bobby ocampo
Senior Member
roger said:
Never did I say that neutral is not allowed to be bonded. However in an Ungrounded system where there is no neutral conductor the bonded EGC is connected to the metal case of the transformer then connected to earth through a grounding rod.
Neutral if connected to earth is solidly grounded. If neutral is not connected to earth then the system is considered ungrounded. If the neutral is connected through a resistor then the system is considered impedance grounded.
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