- #31
jimee
- 1
- 0
IR drop is the issue.
The following is not to be relied on ...
1. A reason that sudden high loads cause a voltage burp
is that the line from a pole transformer to the service
panel can have enough impedance for a significant IR drop.
When the service neutral is in redundant bond to earth
ground near the service drop, that IR delta is reduced.
Ground bond wires carry current flow shared with the
neutral from the pole transformer, assuming that the
pole transformer ground is in place.
2. Outlet neutrals are not good ground returns for a
couple of reasons that I can think of at this time.
A small fault current from hand to hand can be fatal,
so a "redundant" ground wire, with low impedance,
increases the odds of timely fuse or breaker operation,
particularly if the event creating the shock hazard also
damaged the neutral. A surviving ground conductor
can trip a fuse or breaker to avoid a hazard.
Also, a bare or green conductor is less likely to be
disconnected or left unconnected at the service end.
(Outlets without a ground conductor are not hard to fix if
codes allow running a protected wire to a nearby ground.)
The following is not to be relied on ...
1. A reason that sudden high loads cause a voltage burp
is that the line from a pole transformer to the service
panel can have enough impedance for a significant IR drop.
When the service neutral is in redundant bond to earth
ground near the service drop, that IR delta is reduced.
Ground bond wires carry current flow shared with the
neutral from the pole transformer, assuming that the
pole transformer ground is in place.
2. Outlet neutrals are not good ground returns for a
couple of reasons that I can think of at this time.
A small fault current from hand to hand can be fatal,
so a "redundant" ground wire, with low impedance,
increases the odds of timely fuse or breaker operation,
particularly if the event creating the shock hazard also
damaged the neutral. A surviving ground conductor
can trip a fuse or breaker to avoid a hazard.
Also, a bare or green conductor is less likely to be
disconnected or left unconnected at the service end.
(Outlets without a ground conductor are not hard to fix if
codes allow running a protected wire to a nearby ground.)