High Neutral-Earth voltage


Thread Starter


In a 3 phase 415V AC supply, it is found that phase voltages at R, Y, B w.r.t. to neutral is 235, 232, 233. Neutral to earth volatge was found 16V. Phase to earth voltage was found to be 240, 230, 228V. Earthing is proper at this site. What might be the problem at above site?
Check the MEN connection and all neutral and earth connections thereafter.

Also, check that the size of the neutral cable is large enough.

Usual causes of this phenomenon are loose connections, undersize neutral cable, burnt connections.
Responding to Burman's Tue, Nov 16, 4:38pm query:

There appears to be substantial, but undesirable, current flow between neutral and earth. For analysis please provide the following:

1) Is this a new problem? Or one that has existed for a while?

2) Where were measurements made? At source? Elsewhere in system?

3) What are phase-to-phase (R-Y, Y-B. B-R) voltages?

4) What are currents in phase R, Y, B conductors?

5) What is current in neutral conductor?

6) What is current in neutral-to-earth conductor or link?

7) Is system large, i.e, several hundred meters of LV or LT conductors? 3-core? 31/2-core? 4-core? In air? In metallic conduit? Non-metallic duct? Direct buried?

8) What are installation details or construction method of link between neutral and earth?

Phil Corso, PE {Boca Raton, FL, USA}
[[email protected]] ([email protected]
You don't say if the supply is from a generator, but it might be some thing to do with a unbalance load then the neutral conductor carries the unbalance part. Hope the info helps.

Bob Peterson

Sounds like you might have a substantial neutral current and you are reading the voltage drop for this current between earth and neutral.

where are you taking this reading?

measure the current in the neutral.
Either you have a floating neutral or your system is heavily unbalanced. Either way you have a problem.
Check for the neutral connections for any looseness or burnt.
Wher is neutral connected? is it connected or not?
Further try balancing the load if possible.

vb singh

Dinesh K Paramewswran

One thing that can be done is to balance the load on each phases to the maximum extent. This will reduce the Neutral current and hence NEV.

Dinesh K Paramewswran