Home Page News Search Contact Us Language Bar فارسی English
Transformer riddle no.9 - Neutral derived from 3-wire system

To overcome this "oversight" they are proposing to install a local autotransformer of vector group Zn0 to generate a neutral for the load. The "new" neutral will not be earthed at this point however the source where the 3-phase eminates from is a 415v transformer with solidly earthed star point.
they are proposing this to save running a new cable (excavation required). I've never seen this before and have a few questions.
Has anyone had experience of this type of "fix"

The installation is difficult to explain but I can issue a simple diagram if required.
Author : WALKERP
Thu, September 4, 2008 - 11:03
As you have mentioned, they will want to make an artificial neutral point as indicated in following diagram. Theoretical this is possible, but you must check the isolation of UPS grounding system and that artificial neutral bar.
Also the auxiliary transformer must be rated for withstand phase-neutral short circuit current (equal to upstream system earth fault current) additional of normal neutral loads; it seems this point can be increased the cost of mentioned transformer very much.

Author : Hamid - From: IRAN
Fri, July 24th, 2009 - 16:31
Normally the impedence of the Zig - Zag transformer is very high . The earthing transformers normally use Zig-Zag connection to harness this advantage . 
Author : R K Mohapatra - From: India
Submit Your Answer

Change Language :