I have a transformer for troubleshooting. It is a 3 phase DELTA-WYE Step down (11KV/400V) transformer, the low side voltages (secondary) are
Line to line voltages:
RED-YELLOW : 400 V YELLOW - BLUE : 400V BLUE- RED : 400V
Line to Neutral Voltage:
RED-Neutral : 400 V YELLOW - Neutral : 400 V BLUE- Neutral : 05 V
What are the possible causes that might cause the issue? So far I have found that the transformer rating has not been impacted. I could not figure out if the transformer has grounded neutral or not.
What should be the list of causes?