It is my understanding that the mains distribution system (poles along the road, where I live) has occasional earth ground connections of the Neutral wire. Maybe every pole, or just every few poles, to shunt lightning hits to ground. Is this true?

If so, I was wondering if there is a loss due to current also flowing in the earth, parallel to the neutral wire. On one hand, adding a lossy conductor in parallel with a good one should not result in increased loss. On the other, I was taught that "electricity flows on all paths that are available", and that Alternating Current flowing down a ground rod, through an earth path and into another grounded conductor or rod, is very lossy.

Is there any additional loss in the transmission system due to the grounding of the Neutral wire in multiple places along its length?

  • \$\begingroup\$ No. The ground currents are just noise and bypass for interference, although some poorly designed power transformer steel tanks loose some power by induction of stray MMF. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 16 '18 at 18:11
  • \$\begingroup\$ @TonyStewart.EEsince'75 Noise? Different from what is flowing on the Neutral wire 20 feet overhead? I don't understand. \$\endgroup\$ – user56384 Mar 16 '18 at 18:12
  • \$\begingroup\$ “Y” caps may shunt 0.25mA max per SMPS per specs . This is noise and neglible power. N is the return of unbalanced Line currents which are grounded at secondary Y coils for safety only. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 16 '18 at 18:15
  • \$\begingroup\$ @nocomprende Try to calculate the 'additional loss', and you'll see why it's impossible. \$\endgroup\$ – Laszlo Valko Mar 16 '18 at 18:16
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    \$\begingroup\$ @nocomprende Try to calculate that additional loss. And arrive to the conclusion that the additional loss cannot be >0. \$\endgroup\$ – Laszlo Valko Mar 16 '18 at 18:32

The neutral wire is not a perfect conductor, so the earth will carry some current. There must be some loss, by definition.

For a single phase supply, the neutral wire will carry the full-load current and let's say that the wire resistance between load and pole transformer is in the region of 0.01 ohms.

So, if there is 100 amps, the neutral wire losses are 100\$^2\$ x 0.01 = 100 watts.

If the neutral wire is grounded both at the load-end and at the pole-end and that earth ground is (say) 0.1 ohms, the net impedance is 0.01 || 0.1 ohms = 0.009 ohms. With 100 amps flowing the losses are 90 watts.

In other words, the grounding makes the impedance lower and losses are reduced.

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As far as I'm aware there are earthing points on poles carrying transformers but it's unclear whether there are also earthing wires on poles that don't carry ancillary equipment. I can't be 100% sure but I think I've seen earth wires on plain ordinary electric poles. Maybe it's different in different countries and regions?

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    \$\begingroup\$ You can be sure that it varies a lot worldwide. \$\endgroup\$ – user56384 Mar 16 '18 at 19:01
  • \$\begingroup\$ All house power entry points have a Nuetral/Ground/GroundStake which you need to consider of course. The local distribution (at least here in the US is 3 wire Delta. A pole transformer is Delta to Wye for 3 phase or 2 phase (from the Delta) to biphase and is the first point at which a neutral/Ground connection is required. \$\endgroup\$ – Jack Creasey Mar 16 '18 at 19:22
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    \$\begingroup\$ earth to earth connections over a long haul can be as higher than 100 Ohms, so earth is not a perfect conductor either and depends on water content and ionic content. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 16 '18 at 19:36
  • \$\begingroup\$ And now the same for three phase systems please ^ \$\endgroup\$ – PlasmaHH Mar 16 '18 at 20:10
  • \$\begingroup\$ @PlasmaHH feel free to contribute lol \$\endgroup\$ – Andy aka Mar 16 '18 at 20:29

Earth ground resistance between transmission line bonding or "earthing" or "grounding" as they say in the USA is rarely less than the Neutral resistance.

Although unbalanced line currents carried in Neutral may be offset from the next earthing connection and will result in earth currents, these may be 50% but I don't know any power distribution design engineer that would rely on Earth conductance to reduce the cost of the Neutral Wire and thus raise it's resistance more than Earth to Earth resistance between "bonding points".

Earth losses are only critical for local transient protection from lightning and have dramatically reduced protection to discharges at a distance.

“Earthing” is a term used in Europe or other countries that employ International Electric Commission (IEC) standards. The term “earthing” in European or IEC countries is synonymous with the term “grounding” in North America.

  • \$\begingroup\$ Ground, it's not just for Earth anymore. It's funny, because in England they have the phrase "gone to ground" (when hunting). No one says "gone to earth". \$\endgroup\$ – user56384 Mar 16 '18 at 19:02

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