Neutral-earth harmonic resonance

[luc4van]

When carrying out a system analysis During design stage (Variable speed drives connected to 3 transformers in parallel) is it a normal practise to check/measure neutral - Earth harmonics, can this be predicted?

 

[m.s.j]

The neutral path of power system is a suitable path for flowing of 3th harmonic current which can interfere to communication systems. One of known way for elimination this harmful effect is the trapping of 3th and other its multiplier harmonic in delta connection of converter transformers which can be predicted in mentioned VSD system.
For similar discussion you can refer to Transformer riddle No.5 from http://electrical-riddles.com