If your transformer is single phase side grounded (120 only) or delta delta you do not need secondary protection as long as the primary OCPD rating matches the secondary side per volt amp ratio.I'm installing a stand-alone irrigation service for one 5HP centrifugal force motor, plus a irrigation clock. The service is 277/480 so I will be installing a 1KVA transformer, 277 primary 120 secondary for the clock. The branch circuit OLOC protection before transformer will be a fusible safety switch. Question is do a need OLOC protection on the secondary side to the clock.
In English terms if a secondary side protection device needs to be 100 amps at 240 volts you can omit it if the primary side OCPD is 50amps at 480 volts.