NEC Article 210.8 (ed. 2017)  Ground-fault circuit-interrupter protection for personnel shall be provided as required in 210.8(A) through (E).  The ground-fault circuit interrupter shall be installed in a readily accessible location. 

NEC Articles 215.10 (ed. 2017) (feeder circuit breakers), 210.13
(ed. 2017) (branch circuit breakers), and 240.13 (ed. 2017) (main
disconnecting means) detail requirements for when ground fault
protection is necessary. These clauses specify that ground fault
protection must be provided in accordance to the provisions in
NEC article 230.95 (ed. 2017) for wye system configurations
where the following conditions are met:
- The phase-to-ground greater than 150 VAC.
- The phase-to-phase voltage is 600 VAC, or less.
- The feeder circuit breaker is rated for 1000A, or greater.
NEC articles 215.10 (ed. 2017) and 240.13 (ed. 2017) contain
provisions for the exception to these requirements under the
following conditions:
- Ground fault protection is not required for industrial processes
where the hazards are increased by shutting down the process
- Ground fault protection is not desirable for fire pumps.
- Ground fault protection is not required on feeders where there
is up-stream ground fault protection.
NEC article 517.17 (ed. 2017) details the requirements for ground
fault protection within health care facilities. It is required that
two levels of ground fault protection should be supplied, with
protection both on the main circuit breaker, as well as the feeder
circuit breaker. The devices must be coordinated to ensure that
the feeder circuit breaker will trip prior to causing the main circuit
breaker to trip.
NEC article 700.31 (ed. 2017) states that ground fault tripping is
not required on emergency back-up systems, but it is required that
there be a sensing and alarm function for ground fault.
NEC article 701.26 (ed. 2017) states that ground fault protection
is not required, in any form, on legally required back-up systems.
Ground fault alarm is often a preferred indication, and in some
cases may be required (see NEC article 701.5(D); edition 2017).