682.15 Ground-Fault Circuit-Interrupter (GFCI) Protection.
Fifteen- and 20-ampere single-phase, 125-volt through 250-volt receptacles installed outdoors and in or on floating buildings or structures within the electrical datum plane area shall be provided with GFCI protection for personnel.
The GFCI requirements in this article, unless otherwise noted, shall be in addition to the requirements in 210.8. Ground-fault protection shall be provided in accordance with 682.15(A) and (B). The GFCI protection device shall be located not less than 300 mm (12 in.) above the established electrical datum plane.
(A) Outlets. Outlets supplied by branch circuits not exceeding 150 volts to ground and 60 amperes single-phase, shall be provided with ground-fault circuit-interrupter protection for personnel.
(B) Feeder and Branch Circuits on Piers. Feeder and branch-circuit conductors that are installed on piers shall be provided with ground-fault protection not exceeding 30 mA. Coordination with downstream ground-fault protection shall be permitted at the feeder overcurrent protective device.
Exception No. 1: Transformer secondary conductors of a separately derived ac system, operating at voltages exceeding 15 volts ac, that do not exceed 3 m (10 ft) and are installed in a raceway shall be permitted to be installed without ground-fault protection. This exception shall also apply to the supply terminals of the equipment supplied by the transformer secondary conductors.
Exception No. 2: Low-voltage circuits not requiring grounding, not exceeding the low-voltage contact limit as defined in 680.2, and supplied by listed transformers or power supplies that comply with 680.23(A)(2) shall be permitted to be installed without ground-fault protection.

Material taken from the National Electric Code® is reprinted with permission from NFPA 70®, 2020 edition.
National Electrical Code®, Copyright 2019, National Fire Protection Association, Quincy, MA. All rights reserved.