I found this in the specification guide on the Cooper web page.

Quote

4.13 Overcurrent Protection

4.13.1 The overcurrent protection scheme provided with the transformer shall consist of the following checked attributes. If for any reason a special protection scheme is required it will be clearly stated on the inquiry.

[ ] Standard–No overcurrent protection is required with the transformer.

[ ] Protected–Primary overcurrent protection shall be provided by an internally mounted cartridge fuse.

[ ] Protected Plus–Secondary overcurrent and transformer overload protection shall be provided by a breaker installed on the secondary side of the transformer. This breaker shall have the capability to energize and de-energize the secondary service by one hotstick operation. This device shall be used in conjunction with an expulsion fuse on the primary side of the transformer (5-75 kVA).
[ ] Protected Plus (MagneX) – Primary overcurrent and transformer overload protection shall be provided by a breaker installed on the primary side of the transformer. This breaker shall have the capability to energize and de-energize the transformer by one hotstick operation. This device may be used in series with a current-limiting fuse to provide 50,000 A interrupting capability.
[ ] Magnex [ ] Magnex in series with current limiting fuse

Greg Fretwell