Neutral to Earth Voltage

Balance the single phase loads across all phases. High neutral voltage indicates an out-of-balance loading.

HI,

all the loads are balanced. Its all work station loads. the voltage is out put of ups where we are measruring the neutral to earth.

have you tried checking for the connections, there might be open circuits

Just because you have the same type of load on each single phase leg of the three phase service does not mean they are ballanced.

Have you put an amp clamp on each of the three phase legs in the load center? If you see that one leg has considerably more or less current going through it, or if you see that all three legs are vastly different then you have a system that is out of ballance. If you have similar currents in all three legs then is it possible that you have a neutral that either has a bit of thin insulation or one that is inductavely coupled to one of the phases?

Travis

GA !!

GA.

That must be the single most short, correct and perfect answer that I have ever seen!!!

But did the original poster understand it? We will see!!!

Earth is a piss poor conductor. You might want to try tieing all the nuetrals together with a nice stout piece of copper...

With IT installations there is typically a heavy 3rd harmonic component. In three phase systems, this combines in the neutral instead of cancelling. This is one reason for oversized or double neutrals (which you indicated you have if I understood correctly).

A reading of 18V indicates a high voltage drop in your neutral system, which is most likely caused from a poor connection in the system rather than voltage drop over the cable itself. Look for voltage drop over the connections themselves and the voltage from the neutral to ground, starting at your IT station then working back to the source. That should give you a better picture of what is happening.

A second possible, but not so likely cause, is some king of poor connection in the grounding system between the 7th floor and your main ground point. This is not likely due to possible multiple paths and limited current flow (compared with the neutral).

Hope that helps.

Have you verified the UPS is not the source of the difference. The UPS would actualy be creating the output A/C and could be floating higher than input a/c.

If UPS is in reverse bypass, using input a/c to directly supply the output a/c does the same conditions exist

regards

Michael

I suspect you have current flow on your neutral. Are your loads phase to phase, or phase to neutral?

In one of the IT clusters the neutral to earth voltage is as high as 18V at 7th floor. Where as the neutral to earth voltage at other floors such as 1st to 6th floor is 3V only. We have provided 2N for the rising mains.

Hi- Just an experienced Guest: Check your Ground Cable Connections/ if you need a megger to arrive at a zero volts accross a posssible bolted ground cable. We found ground to earth reading that varried. We ended up Cad-Welding the Copper Ground Cables to the Steel Towers @ ALL of Ten Communication Towers. NO MORE GROUND TO EARTH READINGS LARGE ENOUGH TO READ ON A MEGGER. Trust this Idea helps you find your Problem. Grandpa Carl.

A Megger is a device for measuring (hopefully!) Meg Ohms of insulation at high voltages and not generally Ohms, which is a requirement when looking for sources of high resistance above say 1 Ohm in connections.....

Nor did I ever see a possibility for using a Megger to measure volts either.....

Unless of course your Megger had an extra scale for these items (modern version?). The ones that I used in the distant past did not have a means to measure low Ohms or volts, we had to use a separate meter for that...... but times do change!!

If your device had a scale for low Ohms/Volts, may I gently suggest that then one should maybe use the name Ohm/Volt meter as this reflects better the actual job being done, even if the Ohm/Volt meter was made by the firm of Megger!!!

Have a great day.