Original Version

Rule 59.3-D

59.3-D.    Neutral Conductors

The arrangement and continuity of common neutral conductors shall conform to the following requirements:

Cross ties of the neutral conductor shall be made to form a continuous interconnected grid network and there shall be not less than two or more separate and continuous metallic return conductors from the grid network to the substation constituting the source of supply thereto.

If two return conductors only are used, each shall have a minimum conductivity of approximately 50 per cent of the conductivity of the primary phase conductor of the largest overhead feeder serving the area.  (See Table No. 14 of Rule 59.3-B for minimum sizes.)

If more than two return conductors are used, the current-carrying capacity of the return system shall be such that a break in any one path shall leave two or more return paths which, combined, shall have a minimum area of approximately 50 per cent of the area of the primary phase conductor of the largest overhead feeder serving the area, thus providing adequate current-carrying capacity for full load current.  (see Table No. 14 of Rule 59.3-B for minimum sizes.)

Primary neutral conductors or secondary neutral conductors, where continuous, may be used as a return loop from a common neutral provided they are of sufficient current-carrying capacity as specified in Rule 59.3-B and provided that they are grounded throughout in accordance with the requirements for common neutral line conductors as specified in Rule 59.4-B. Primary or secondary neutral line conductors so used shall be carried in their normal primary or secondary positions respectively.

Strikeout and Underline Version

Rule 59.3-D

59.3-D.    Neutral Conductors Arrangement And Continuity

The arrangement and continuity of common neutral conductors shall conform to the following requirements:

(1)    Continuity: Cross ties of the common neutral conductor shall be made to form a continuous interconnected grid network. and

(2)    Minimum Number of Return Paths: there shall be not not be less than two or more separate and continuous metallic return conductors from the grid network to the substation constituting the source of supply thereto.

(3)    Two Return Conductor Paths: If only two return common neutral conductors paths only are used, each path shall have a minimum conductivity of approximately 50 per cent of the conductivity ampacity of not less than one-quarter (25%) that of the largest related primary phase conductor, provided that the short time ampacity of the common neutral conductor is maintained of the largest overhead feeder serving the area.  (See Table No. 14 of Rule 59.3-B for minimum sizes.).

(4)    More Than Two Return Conductor Paths: If more than two return common neutral conductors paths are used, the current-carrying capacity ampacity of the return system shall be such that a break in any one path shall leave two or more return common neutral paths. which,  These combined paths, shall have a minimum conductivity ampacity of not less than one-quarter (25%) that of approximately 50 per cent of the conductivity of the largest primary phase conductor of the largest overhead feeder serving the area, provided that the short time ampacity of the common neutral conductor is maintained thus providing adequate current-carrying capacity for full load current.  (see Table No. 14 of Rule 59.3-B for minimum sizes.).

(5)    Primary and Secondary Neutral Conductors: Primary neutral conductors or secondary neutral conductors, where continuous, may be used as a return loop from a common neutral provided they are of have sufficient current-carrying capacity ampacity as specified in Rule 59.3-B and provided that they are grounded throughout in accordance with the requirements for common neutral line conductors as specified in Rule 59.4-B. Primary or secondary neutral line conductors so used shall be carried in their normal primary or secondary positions respectively.

Final Version

Rule 59.3-D

59.3-D.    Arrangement And Continuity

The arrangement and continuity of common neutral conductors shall conform to the following requirements:

(1)    Continuity: Cross ties of the common neutral conductor shall be made to form a continuous interconnected grid network.

(2)    Minimum Number of Return Paths: there shall not be less than two or more separate and continuous metallic return conductors from the grid network to the substation constituting the source of supply thereto.

(3)    Two Return Conductor Paths: If only two return common neutral conductors paths only are used, each path shall have a ampacity of not less than one-quarter (25%) that of the largest related primary phase conductor, provided that the short time ampacity of the common neutral conductor is maintained.

(4)    More Than Two Return Conductor Paths: If more than two return common neutral conductors paths are used, the ampacity of the return system shall be such that a break in any one path shall leave two or more return common neutral paths. These combined paths, shall have a minimum ampacity of not less than one-quarter (25%) that of the largest primary phase conductor of the overhead feeder serving the area, provided that the short time ampacity of the common neutral conductor is maintained.

(5)    Primary and Secondary Neutral Conductors: Primary neutral conductors or secondary neutral conductors, where continuous, may be used as a return loop from a common neutral provided they have sufficient ampacity as specified in Rule 59.3-B and are grounded throughout in accordance with the requirements for common neutral conductors as specified in Rule 59.4-B. Primary or secondary neutral line conductors so used shall be carried in their normal primary or secondary positions respectively.