Original Version
Rule 59.4-B
59.4-B. Neutral Conductors
(1) Location: The common neutral grid system shall be grounded at intervals not greater than 1000 feet. On branch circuits extending from a grid, where return loop paths are not available, the common neutral line conductor shall be grounded at intervals not greater than 500 feet. Each transformer installation on a branch circuit without a loop return shall be so located that there will be not less than one grounds, each of a resistance not greater than 3 ½ ohms, on each side of the transformer installation.
(2)
Resistance: Where a common neutral
system is used the resistance of the continuous metallic neutral grid to ground
at any point shall not exceed 3 ½ ohms at any time.
If, after definite effort has
been made, it is found not practicable to meet the above requirement, the
following alternate requirement will be accepted:
The resistance between any point of said grid and the ground connection at the substation shall not exceed 1 ohm, and furthermore, the resistance of the ground connection at the substation either shall not exceed 1 ohm or, if in excess of 1 ohm, shall be lower than that that of any individual ground connection on the grid and in no case in excess of 2 ohms.
Measurement of resistance by any approved method is recognized. In lieu of measurements of resistance of the neutral conductor under the second alternative prescribed above, approved joints and demonstrable calculations will be accepted.
Strikeout and Underline Version
Rule 59.4-B
59.4-B. Neutral Conductors
(1)
Location: The common neutral grid system
shall be grounded at intervals not greater than 1000 feet. On branch circuits extending from a grid,
where return loop paths are not available, the common neutral line
conductor shall be grounded at intervals not greater than 500 feet. For Each transformer installation
installed on a branch circuit without a loop return, the transformer
shall be so located that there will be not less than one grounds, each
of a resistance not greater than 3 ½.5 ohms, on each side
of the transformer installation.
(2)
Resistance: Where a common neutral
system is used, the resistance of the continuous metallic neutral grid
to ground at any point shall not exceed 3 ½.5 ohms at any
time.
EXCEPTION: If, after a definite effort has been made, it is found not practicable to meet the above requirement, the following alternate requirement will be accepted:
The
resistance between any point of said the continuous metallic neutral
grid and the ground connection at the substation shall normally not exceed 1
ohm,. However, if and furthermore, the resistance exceeds
1 ohm, it of the ground connection at the substation either shall not
exceed 1 ohm or, if in excess of 1 ohm, shall be lower than that that of
any individual ground connection on the grid, but and in no case in
excess of shall it be greater than 2 ohms.
(3) Measurement of Resistance:
Measurement of resistance by any approved suitable method is
recognized.
Note:
Under the requirements of
Rule 59.4-B2. In lieu of
measurements of resistance of the neutral conductor under the second alternative
prescribed above, when the resistance exceeds 1 ohm but is to be less
than 2 ohms, approved suitable ground rod connections( joints)
and demonstrable calculations, instead of neutral conductor resistance
measurements, will be accepted.
Final Version
Rule 59.4-B
59.4-B. Neutral Conductors
(1) Location: The common neutral grid system shall be grounded at intervals not greater than 1000 feet. On branch circuits extending from a grid, where return loop paths are not available, the common neutral conductor shall be grounded at intervals not greater than 500 feet. For Each transformer installed on a branch circuit without a loop return, the transformer shall be so located that there will be not less than one grounds, each of a resistance not greater than 3.5 ohms.
(2) Resistance: Where a common neutral system is used, the resistance of the continuous metallic neutral grid to ground at any point shall not exceed 3.5 ohms at any time.
EXCEPTION: If, after a definite effort has been made, it is found not practicable to meet the above requirement, the following alternate requirement will be accepted:
The resistance between any point of said the continuous metallic neutral grid and the ground connection at the substation shall normally not exceed 1 ohm. However, if the resistance exceeds 1 ohm, it shall be lower than that that of any individual ground connection on the grid, but and in no case shall it be greater than 2 ohms.
(3) Measurement of Resistance: Measurement of resistance by any suitable method is recognized.
Note: Under the requirements of Rule 59.4-B2. when the resistance exceeds 1 ohm but is to be less than 2 ohms, suitable ground rod connections( joints) and demonstrable calculations, instead of neutral conductor resistance measurements, will be accepted.