What is the requirement for guarding of live parts over 600 volts?

Protect electrical installations as follows:

• Electrical installations in a vault, room, or closet or in an area surrounded by a wall, screen, or fence, access to which is controlled by lock and key or other approved means, are considered to be accessible to qualified persons only.
• Use a wall, screen, or fence to enclose an outdoor electrical installation to deter access by persons who are not qualified. A fence may not be less than 7 feet in height, or a combination of 6 foot or more of fence fabric and a 1-foot or more extension utilizing three or more strands of barbed wire or equivalent.
• Design nonmetallic or metal-enclosed equipment located outdoors and accessible to the general public so that exposed nuts or bolts cannot be readily removed, permitting access to live parts.
• Where nonmetallic or metal-enclosed equipment is accessible to the general public and the bottom of the enclosure is less than 2.44 m (8.0 ft) above the floor or grade level, the enclosure door or hinged cover shall be kept locked.
• Except for underground box covers that weigh over 100 lb, ensure doors and covers of enclosures used solely as pull boxes, splice boxes, or junction boxes are locked, bolted, or screwed on.