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General Order 64-A


Section V


Detailed Construction Requirements For Supply Lines

(Class H, L and T Circuits)


57.4    Clearances.


A.    General.

The normal clearances of Tables 1 and 2, for open wire conductors, apply except where modified herein.

Cables treated as in Rule 57.8, attached directly to one side of poles, may have the clearances specified in Table 2, Cases 9, 10 and 11, and Columns D, E and F, reduced to 2 feet where applied between cables if all cables are of one ownership.


B.    From Open Wire Conductors

Cables and messengers attached to surface of poles may be installed at a minimum 4 foot vertical separation from open wire supply conductors installed on cross arms, provided they are protected as required in Rule 57.7-A.


C.    Between Cable Conductors and Cables.

Properly insulated cables, duplex, triplex or paired conductors, whether single or grouped, are considered single conductors and , therefore, no clearance is required between the conductors which comprise them.  The clearances of Table 2, Case 15 do not apply in this instance, nor do they apply to wires of the same phase or polarity between which there is no difference in potential.


D.    Between Cables and Messengers.

Cables supported by messengers are not required to be any specified distance from the messenger.  Table 2, Case 1 does not apply in this instance, nor does it apply where messengers of one system intersect, branch or cross.


E.    Above Trolley Contact Conductors.

Cables and messengers which are suitably protected may have a clearance of not less than 4 feet above the trolley contact conductor, provided they are not less than 23 feet above tracks on which standard freight cars are not transported or proposed to be transported.


F.    From Poles

Cables and messengers, grounded and bonded as specified in Rule 57.8, are considered as conductors of 0-750 volts and may be attached directly to the supporting poles or structures at lesser clearances than specified in Table 1, Cases 7 and 9.


G.    From Buildings and Other Structures.

Cables and messengers installed in accordance with Rule 57.8 are not required to clear sides of buildings or other structures any specified distance, but they shall be installed so that they do not interfere with the free use of fire escapes, exits, etc., and shall be so arranged as to hamper and endanger fireman as little as possible in the performance of their duties.