Re: 4160V to 480V 1000KVA Unit Substation Disconnect
Lest someone thinks it applies only to switchgear, I would read Section 490.22 in context of Section 490.1.
For most Equipment over 600V applications, “In Sight From” as defined in Article 100 is often meaningless. This does not mean a disconnecting switch is the only solution, but “isolation” means more than simply disconnecting the transformer’s feeder at a remote location since 490.22 refers to an “item of equipment.” The feeder conductors are “equipment” themselves as defined in Article 100.
This was one of the reasons for Exception 1 to 430.102(A). But remember it only applies to motors. There is nothing analogous in Article 450 for transformers.
Depending on the AHJ, various taps installed per Section 240.21 may be considered incidental parts of the “item of equipment.”
Robert B. Alexander, P.E.
Answers based on 2014 NEC unless otherwise noted.