The "Dummy Fuses" referenced in Electure's posted Hyperlink, are useful in 3 Pole Safety Switches; where the System used is a 3 Phase 3 Wire Corner Grounded Delta.
This effectively opens all 3 Conductors (both Ungrounded Conductors and the Grounded Conductor) simultaneously, and keeps the Grounded Conductor "Solid" (No OCPD in Series) at the Disconnect / Safety Switch.
Footnote: When such an item is seen by "4 Wire Wye-Guys only", the reactions by those unfamiliar with Corner Grounded Systems range from a simple "Whaddaheck???" to "Evacuate The Building!!!"
After which comes the difficulty of trying to explain why the Identified (i.e. Grounded) Conductor is One of the Three Wires for this 3 Phase 3 Wire Branch Circuit - and why White or Gray Insulation / Tape on this Conductor is Code Compliant...
Most grasp the concept and accept the System's "Differences", while only a few (be they obnoxious, arrogant, or simply from Mule-Level Reluctance), refuse to accept any part of such an Alien System's use, operation and Code Compliance.
(Note: I mention the latter, due to a few ugly debates from past installations...)
--Scott (EE)
