Pennsylvania Code › Title 34 - LABOR AND INDUSTRY › Part I - Department of Labor and Industry › Chapter 39 - SAFETY STANDARDS-GENERAL › Subchapter B - ELECTRIC SAFETY › METHODS OF PROTECTIVE GROUNDING › Section 39.66 - Nature of ground connection

Current through Register Vol. 54, No. 28, July 13, 2024
(a)
Permanence.
The ground connections shall be permanent and
					 effective and made as indicated in subsection (b), if possible, or else as
					 prescribed in subsection (c), (d) or (e). Reference should also be made to
					 §
											39.69 (relating to ground
					 resistance).
(b)
Piping
					 system.
For circuits, equipment, and arresters at supply stations,
					 connections shall be made to all available active continuous metallic
					 underground water piping systems between which no appreciable difference of
					 potential normally exists, and to one such system if appreciable differences of
					 potential do exist between them. At other places connections shall be made to
					 at least one such system, if available. Gas piping shall not be used.
					 References should be made to §§
											39.65 and
					 39.68 (relating to ground
					 conductor; methods of ground connection). The term "available," as used in this
					 rule, shall mean ordinarily within 500 feet for stations. The protective
					 grounding of electrical circuits and equipment to water pipe systems in
					 accordance with this Subchapter shall always be permitted, since such grounding
					 offers the most efficient protection to life and property and is not injurious
					 to the piping systems.
(c)
Alternate methods.
If underground metallic piping systems are
					 not available, other methods which will secure the desired permanence and
					 conductance may be permitted. Where available, metal well casings, local metal
					 drain pipes, and similar buried metal structures of considerable extent may be
					 used in lieu of extended buried water-piping systems. Ground connection may be
					 made to the steel frame of a building containing the grounded circuits or
					 equipment, to which frames of machines and other noncurrent-carrying surfaces
					 should also then be connected. In such cases the building frame shall be itself
					 well grounded by effective connection to the ground which may require
					 artificial grounding for steel frame buildings supported on masonry or
					 unreinforced concrete footings.
(d)
Artificial grounds.
If resort to artificial grounds is
					 necessary, their number shall be determined by the following requirements:
(1) No more than one artificial ground is
					 required for lightning arresters, except for large current capacity. At least
					 two grounds are required for low voltage alternating current distribution
					 circuits at transformers or elsewhere.
(2) If no part of the circuit or equipment
					 protected may be reached by persons while they are standing on the ground or
					 damp floors, or by persons while touching any metallic piping to which the
					 ground wire is not effectively connected, a single artificial ground may be
					 used even if its resistance exceeds that specified in §
												39.69. In such cases guards should
					 be provided for the ground conductor in accordance with §
												39.65(c) wherever
					 it is otherwise accessible, or to provide insulating mats or platforms so
					 located that persons cannot readily touch the ground conductor without standing
					 on such mats or platforms.