Cause of High Neutral Current


Thread Starter


Our power distribution network is 11/0.433kV Dyn11 transformers. We have seriously high neutral currents even though the loads are fairly balanced. Example of measured currents on a 500KVA transformer are Red-450A, Yellow-420A, Blue-465A, Neutral-120A.

Please can someone explain this?
Solo... please provide additional information:

(1) You mentioned transformer(s)in plural. Are they connected to the same 433-V bus?

(2)If the answer to 91) is yes, then what are their nameplate parameters identical?

(3) The current values you listed yield an Ampere-
Unbalance-Factor, AUF, greater than 5%, i.e, 5.6& if you comply to the NEMA standard and 5.9% if IEC is used. This value is not considered a well-balanced 3-Phase system.

(4) Can you furnish Line-Voltage and Phase-Voltage value?

(5) Can you provide comparable Voltage and Ampere values for the 2nd transformer? And others, if they exist?

(6) Can you provider comparable Voltage and Ampere values for the primary-side of the transformers?

Regards, Phil Corspo (cepsicon[at]aol[dot]com)
Even we are facing the same problem, we have 5 LT transformers 6.6kV/433V 2MVA DYN11. New sixth transformer with same specifications is installed but it is sharing more neutral current.

R-1500 Y-1510 B-1590 N-140 Amperes

waiting for your reply

the current values you listed yield an Ampere-Unbalance-Factor, AUF, of 3.7% if you comply with NEMA standards and 3.8% if you comply with IEC standards.

Can you answer the questions I listed in Solo’s post as well as the two below?

(7) What is the current magnitude measured in the neutral-to-earth conductor?

(8) What type of secondary loads are connected between the phase lines and neutral!

Phil Corso