Transformer Banking (Closed Delta)

[Plinko]

Fellow Engineers,

According to the second edition of the Distribution Transformer Handbook (pg. 49, Richard Alexander), when a lighting tfr and a power pot are both feeding a load, he says to close the lighting tfr first when going on-line....and open the lighting tfr last when going off-line. It is said to provide better voltage stability and reduce fuse blowing.
An X-Pacific Corp. lineman brought to my attention that they were trained just the opposite, and gave the same reasoning.
My question is what exactly is the safest way of closing in a delta bank? And why?

Thanks in advance....Plinko

 

[busbar]

Based on §7 of IEEE std C57.105-1978 Application of Transformer Connections in Three Phase Distribution Systems, 12kV {and higher} delta-connected transformer banks are more susceptible to ferroresonant overvoltage compared to solidly-grounded wye, and single-pole switching is generally required to initiate ferroresonance.

The referenced material does not specifically mention any fuse-closing order having an undesirable effect. Didn’t find anything specific in Lineman’s and Cableman’s Handbook, 6th edition or J&P Transformer Book, 11th edition.

 

[prc]

Plinko,
Where will we get the distribution hand book that you have mentioned?who are the publishers for this book?

 

[Plinko]

PRC,

I go through Alexander Publications.

http://www.alexanderpublications.com

It seems they have just about every "pocket guide" known to the electrical utility world.