Three Phase voltage drop: RED VS Ground

Thread Starter


Joined Sep 6, 2018
I am facing a problem with one of my power supplies that a voltage drop on the phase VS ground is coming down (207V) which supposed to be 220-230V. Phase to phase voltages are 380 V & phase to neutral voltages are 230, only one phase to gnd has a drop as below:
L1:Gnd : 207V (Drop)
L2:Gnd : 228V (OK)
L3:Gnd : 229V (OK)

My supply is three phase Y-transformer 380/230VAC, connected to residential building which have many 3-phase pumps, fans & compressors. This drop causing many panels which have the phase failure/monitoring relays to trip all the time because of phase unbalance. Any suggestions for a solution?


Joined Dec 29, 2008
Are you saying that the voltage drop is conclusively due to inductive loads on one phase? Have you measured phase currents, including the neutral wire?


Joined Mar 30, 2018
I would investigate the reason for the large volt-drop on the phase.
This is likely to be due to a high current draw and/or increased line impedance (on that phase).