Original General Order 128

Section II

Definitions Of Terms As Used In These Rules

21.5    Grounded means connected to earth by an intentional ground connection or by an unintentional conducting path.

A.    Effectively Grounded (Effective Ground) means permanently connected to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to prevent the building up of voltages which may result in undue hazard to connected equipment or to persons.

If an impedance of less than 25 ohms is not obtained, the equivalent of a ground conductor not less than No.6 A WG copper connected to two corrosion resisting rods, not less than i inch in diameter and 8 feet in length and continuous throughout, driven to a minimum depth of 8 feet in the earth at not less than 6 foot centers, will be considered an effective ground for the purpose of these rules.