All temporary electrical installations on construction sites must comply with NFPA 70 (National Electrical Code) and applicable local electrical codes. Temporary electrical power must originate from an approved source such as a service panel, generator, or another properly installed electrical system. All temporary wiring must be approved for the locations where it is installed and must be protected from physical damage. Flexible cords and cables must be rated for wet locations if used outdoors or in wet environments. Ground fault circuit interrupter (GFCI) protection is mandatory for all temporary electrical receptacles on construction sites operating at 150 volts or less to ground. All temporary equipment used to supply power must have a ground fault protective device or equivalent ground-fault protection. Extension cords must be inspected before each use for damage, cuts in insulation, or missing ground pins. Cord sets must be three-wire types with a ground conductor to reduce shock hazard. Receptacles must be properly grounded and must not be altered or modified. All electrical equipment must be rated for the environment where it is used. Equipment in wet locations must be rated for wet or damp locations. All personnel working with electricity must be trained on electrical hazards and safe work practices. Lockout/tagout procedures must be used when servicing electrical equipment. Only qualified persons may perform electrical work.