FilterGuy
Solar Engineering Consultant - EG4 and Consumers
This 'conversation' is exactly why I say the word 'ground' is so overused, misused and misunderstood.
At the risk of sounding like a broken record, I will repeat: The System of Equipment Grounding Conductors, Grounding Electrodes and Neutral-Ground bonding serves two distinctly separate purposes.
Edited for clarity of meaning
1) It provides a low impedance path to ensure breakers/fuses pop in the event of a ground fault. This has nothing to do with a 'zero voltage' reference and the grounding electrodes tieing the system to earth ground are not needed for this purpose. It is simply ensuring that if there is a short between the hot wire and any of the metal bonded together with the equipment grounding conductor, there will be enough current to pop the breaker or blow the fuse.
2) It 'anchors' circuit voltage to earth potential so it does not float to some arbitrarily high value. This is done by tying the EGC system that is also connected to the neutral of the power system to earth ground using the grounding electrodes. The only relation to poping fuses or tripping breakers that tying to earth ground has is that it uses the same EGC system and N-G bonds that the Ground fault protection uses.
Both purposes are important. If I had to pick a 'primary' purpose I would say it is the ground fault protection because systems can be built without earth grounding.
At the risk of sounding like a broken record, I will repeat: The System of Equipment Grounding Conductors, Grounding Electrodes and Neutral-Ground bonding serves two distinctly separate purposes.
Edited for clarity of meaning
1) It provides a low impedance path to ensure breakers/fuses pop in the event of a ground fault. This has nothing to do with a 'zero voltage' reference and the grounding electrodes tieing the system to earth ground are not needed for this purpose. It is simply ensuring that if there is a short between the hot wire and any of the metal bonded together with the equipment grounding conductor, there will be enough current to pop the breaker or blow the fuse.
2) It 'anchors' circuit voltage to earth potential so it does not float to some arbitrarily high value. This is done by tying the EGC system that is also connected to the neutral of the power system to earth ground using the grounding electrodes. The only relation to poping fuses or tripping breakers that tying to earth ground has is that it uses the same EGC system and N-G bonds that the Ground fault protection uses.
Both purposes are important. If I had to pick a 'primary' purpose I would say it is the ground fault protection because systems can be built without earth grounding.
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