Different voltage readings between "L1 & E" & "L3 & E"

Thread Starter


Joined May 3, 2017

I am not sure if I am posting on the correct place but I need some clarification on a problem I faced at work.

I am working on an oil rig and there is an electrical test panel on board. There are various output from this test panel - fixed AC & DC output and variable AC & DC output ranging from 0~500V.

On the fixed single phase AC230V test terminals, I measured L1 to E - the reading was AC100V but when I measured L2 to E, the reading was about AC300V. Should the readings be some what the same? Measurement between L1 and L2 was about AC230V.

Can someone explain to me what is the problem?

Thank you in advance.


Joined Sep 20, 2005
What is the voltage between L1 and L2? It looks like a loose neutral to me. And do you have a TN-C system or TN-S, since you E probably means earth and you didnt mention the neutral?


Joined Jul 13, 2015
As you said L1 AND L2 measured a 230VAC. Thats seem ok and good.
Just to clear up ,E ,Stand for earth and N, stand for neutral.
A normal getting the readings in a single phase as you mentioned, you need to checked the proper and sure point
where this neutral line that is missing. But you have an E, earth which is not the proper reference point.
Please verify if the neutral wire is connected to your panel.To see how to know the E(earth) and the N(neutral), this two points
if you try to measure any two wire it should reading almost zero volts. ABOVE zero is dangerous(leakage somewhere).


Joined Sep 20, 2005
missed that you already said that L1-L2 is around 230V, well it actually should be aroud 380-400V, so there seems to be something wrong with the whole supply.