What happen to the electric meter if the neutral touch ground and current flows? - Page 1
Forum section: electronics / beginners

author: tigrou
author_rank: Regular Contributor
timestamp: May 24, 2021, 01:20:16 pm
content: If for some reason the neutral touch the ground (eg : detached wire in some electric appliance), and some current flow trough the ground, what happen to the electric meter, will it be able to measure that current flow ?We assume no GFCI is installed (otherwise AFAIK it should trip immediately)I think there is two cases :1) some current flow between neutral and ground because there is some potential difference between the two (AFAIK in theory it should be zero but there can be a difference between the ground of the house and the one where the place where the 3 phases are transformed to 3 phases + 1 neutral, using a delta wye transformer).2) some current flow between live and ground instead of live to neutral because some appliance is connected (eg : electric heater).For case 1) and 2), let's say I have 5A flowing, what will happen to the electric meter ? will it be able to measure that current (or is it only able to measure live/neutral) ?Here is some meter schematic I found :There is 3 coils : one directly between live and neutral and two other ones in series with the load.Unfortunaltely it does not tell which side is live or neutral (but does it really matter?)

author: Zero999
author_rank: Super Contributor
timestamp: May 24, 2021, 01:27:45 pm
content: The current through the live is measured, so if the load is connected to earth, rather than neutral, it will carry on working. Of course this is assuming the RCD/GFCI doesn't trip. The general advice is don't use the earth, rather than neutral as a return path for current. If the earth becomes broken, it will cause metal surfaces to float at a dangerous voltage.

author: tigrou
author_rank: Regular Contributor
timestamp: May 24, 2021, 01:35:13 pm
content: Quote from: Zero999 on May 24, 2021, 01:27:45 pmso if I understand correctly, 2) will be monitored by meter and 1) won't be.

author: CaptDon
author_rank: Super Contributor
timestamp: May 24, 2021, 01:36:55 pm
content: It will still measure the current flow and voltage and maintain accurate consumption readings. In older house wiring the neutral and earth are bonded at several places anyway. Out at the utility pole the neutral is also usually bonded to a ground lead at the base of the pole where the transformers are located (assuming the vandals haven't cut them and stolen the copper).

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 24, 2021, 02:20:15 pm
content: The current flow in the hot wire should be the same as the current in the neutral plus ground. The meter should indicate the current in the hot wire.

author: fordem
author_rank: Regular Contributor
timestamp: May 24, 2021, 02:30:10 pm
content: Depending on the electrical code where you are, the neutral will be bonded to the ground at some point - in the US it's commonly done at the building entrance, in the UK, I believe it's done at the distribution transformer, I can't say for any other countries, but, either way, current flow between ground & neutral should be minimal, and the meter reading is not affected.

author: Zero999
author_rank: Super Contributor
timestamp: May 24, 2021, 09:36:28 pm
content: The top connection is the neutral, which is bonded to earth. Any current flowing through the live, will be measured, whether it returns via the neutral, or earth.