How to check phase,neutral and ground of ac wire using multimeter

Lukoz

Joined Oct 3, 2015
5
Hi everyone ,

I am bit confused regarding this .

When you check E - P its shows 220V , E to any mettal part which is toching the ground it flutuates from 68 to 220V and after some time become constant 220V.
E - N at the same time shows 6.0 V

Now my question is how do i legitmately look for the earth funtionality with a Multimeter . If the earth is reliable or not ?

mcasale

Joined Jul 18, 2011
210
It sounds like you're working with 220VAC, correct? Single phase or ???
E = Earth Ground?
N = Neutral?
P = Power??
Please verify what you are measuring.

My experience with meters is that they do not measure phase shift. You'll need some type of 'scope for that.

If you really have 6 VAC between Earth & Neutral, something is wrong.

Joined Jul 18, 2013
28,688
For a simple quick test you can use a regular M.M. to check if a conductor is at ground potential, but in commercial practice either a special meter is used or a system of ground rods using AC current to test the validity of a certain ground conductor.
Another simple alternative is to use a 100w lamp from a known live conductor to the conductor identified as the Earth Ground and check to ensure that the voltage across the lamp is identical to the voltage between the live conductor and neutral.
IOW pass a current through the grounded conductor.
Max.

crutschow

Joined Mar 14, 2008
34,452
Phase measurement requires an oscilloscope or a dedicated phase detection circuit.
For example, here's a digital circuit phase detector circuit that will tell whether one phase is leading or lagging the other.

Joined Jul 18, 2013
28,688
I think the OP just wanted to confirm if he has a valid Earth ground conductor.
In my day we used to use a Earth resistance Megger to validate an installation.
Max.

Alec_t

Joined Sep 17, 2013
14,316
Another simple alternative is to use a 100w lamp from a known live conductor to the conductor identified as the Earth Ground
That should trip an Earth-leakage circuit breaker in a few mS, but won't necessarily identify whether the earth impedance is too high.

Joined Jul 18, 2013
28,688
To validate the ground net for Transmission towers and local distribution transformers we used the three rod system using a AC supply, the lamp test is a simple form of this and should show up any immediate weaknesses, e.g. if the lamp is dim or does not light he has a problem..
Max.

Lukoz

Joined Oct 3, 2015
5
YEs its 220V Phase to neutral , E = earth from distribution board to the earth rod . There is no specifics for power , i mean there is no permanent load .

There are around 400 such Db's in this site which serves as temporary power supply for the purpose of construction .

My specific question is how to measure earth reading of a Db with M.M , you know at times its hard to check if the earth cable has damaged or not , so we need a quick method to check .

Usual method is to check by phase and earth which should be 220 V , earth to neutral be zero . But i am getting PH - E 216 V to 220V and
E - N 6 and above . Please suggest .

alexheins3

Joined Mar 7, 2016
1
oohh..lots of ideas.. I gotta start reading!

Dodgydave

Joined Jun 22, 2012
11,303
Start by doing an Earth loop impeadance (Ze) test to establish that there is an earth present at the DB, then test the phase to neutral voltage and phase to earth.

Ze testing

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Joined Jul 18, 2013
28,688

Max.

Lukoz

Joined Oct 3, 2015
5

Hi Max ,

The attachment is not clear .

Lukoz

Joined Oct 3, 2015
5
Start by doing an Earth loop impeadance (Ze) test to establish that there is an earth present at the DB, then test the phase to neutral voltage and phase to earth.

Ze testing

Is this what you mean(attached) . Earth ressitence is already done for the earth Rods and connections which is brought to below 3 ohms