Posted by John T on January 14, 2023 at 04:05:41 from (174.211.104.233):
In Reply to: electrical question posted by gbs on January 13, 2023 at 20:22:27:
gbs, more good electrical questions, those and legal draw out the most opinions lay as well as professional, lots of good people here all willing to help yayyyyyyyy. Although Im longgggggggg retired as a power distribution design engineer I will try to explain how it was done when I last practiced pursuant to the then NEC guidelines.
1) Out on the pole the HV aerial Primary Neutral was bonded to driven ground rods at every 3rd (or 4th?) power pole, this was for lightning and surge suppression and to keep the grid at one common low voltage reference IE mother earth.
2) On the LV secondary out of the transformer the 240 volt winding was tapped in its center (which left two legs of 120 each with respect to the center Neutral 180 out of phase or 240 line to line) and that center tap LV Secondary Neutral was again bonded to a driven into earth ground rod.
3) Three wires L1 L2 and Neutral are brought to the homes panel.
4) At the Panel (or first disconnect) the Neutral IS ONCE MORE connected to all readily available GROUNDING ELECTRODES (such as driven rod or rods) PLUS the Neutral Buss is bonded to the Ground Buss. On some panels theres only one common NG Buss (if main panel) while others there are two Busses and a cross Tie Bar (or screw) is used to bond the two busses together (if main panel)........ Thats the Neutral Ground BOND..
5) The panels case frame also needs bonded to the Ground Buss which may be by a grounding screw that connects the frame to the buss.
BOTTOM LINES
Earth Grounding of BOTH HV Primary and LV Secondary NEUTRALS is for lightning and surge suppression and to keep the grid at one common low voltage reference. HV and LV Neutrals at power pole are earth grounded and again at the home the LV Secondary Neutral is earth grounded
At the main panel (or first disconnect) as above the Neutral is AGAIN earth grounded PLUS Neutral is Bonded to the Ground Buss (cross tie bar or screw or one buss for both N and G)
The panels case/frame ALSO needs bonded to the Ground Buss and the Neutral needs bonded to the Ground Buss and grounding screws can be used for that.
YES there is redundancy as the Neutral (HV and LV) js earth grounded at many locations,,,,,,,,, and the N needs bonded to Ground,,,,,,,,,and the case/frame needs bonded to the Ground Buss..
NOTE although Im rusty on the latest NEC and codes Im pretty sure this has NOT changed since I retired but no warranty. Where fire and life safety are concerned consider consulting current practicing professional electricians and engineers and the NEC in addition to whats offered here me certainly included
Best Wishes
John T Headed to Florida Flywheelers this morning yayyyyyyyy
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