Hello to everyone,
I'm dealing with a voltage drop issue that I can't explain. I would be grateful if anyone could provide elements of solution.
First step was to measure voltages on the load side of a 630 kVA transformer. Even under load, measured voltages are good and quite well balanced : 220V between neutral and phases, 380V between each couple of phases. I made these measurements on the general breaker A.
According to this, my first conclusion is that there's not a voltage drop in the line side as nominal phase to phase voltage is 380V in this area.
General breaker feeds a subpanel which has its own breaker B.
Length of the cables are about 200 ft. Each phase is connected by a 3*150 mm2 copper cable. That corresponds to 3*AWG300. For each of the 3 cables of each phase there's a load of 130A so a total of about 400A per phase.
According to theses values, I should have a voltage drop of only some volts.
However when measuring voltages on breaker B under load, I find only 203-204 V neutral to phase and about 350 V phase to phase. Voltages are also well balanced.
As I can't explain this voltage drop based on cables losses, I don't see how I should consider this issue and how to solve it.
Thank you all for your time and help.
I'm dealing with a voltage drop issue that I can't explain. I would be grateful if anyone could provide elements of solution.
First step was to measure voltages on the load side of a 630 kVA transformer. Even under load, measured voltages are good and quite well balanced : 220V between neutral and phases, 380V between each couple of phases. I made these measurements on the general breaker A.
According to this, my first conclusion is that there's not a voltage drop in the line side as nominal phase to phase voltage is 380V in this area.
General breaker feeds a subpanel which has its own breaker B.
Length of the cables are about 200 ft. Each phase is connected by a 3*150 mm2 copper cable. That corresponds to 3*AWG300. For each of the 3 cables of each phase there's a load of 130A so a total of about 400A per phase.
According to theses values, I should have a voltage drop of only some volts.
However when measuring voltages on breaker B under load, I find only 203-204 V neutral to phase and about 350 V phase to phase. Voltages are also well balanced.
As I can't explain this voltage drop based on cables losses, I don't see how I should consider this issue and how to solve it.
Thank you all for your time and help.