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General Order 64-A

 

Section IV

 

Strength Requirements For All Classes Of Lines

 

49.4    Conductors

 

A.    Material

Open wire conductors shall be of copper, copper covered steel galvanized iron or steel or other corrosion-resisting metal, not subject to rapid deterioration.

 

B.    Size

The minimum sizes of wires of various materials which shall be used for the several classes of construction and loading are listed below.  These minimum sizes shall obtain in both urban and rural districts.  Larger sizes of wire than those shown in table will often be necessary to maintain reasonable sag and at the same time provide the required safety factors of Rule 44, ground clearances of Table 1, and wire clearances of Table 2.

The minimum size of wire given in Table 7 is dependent upon spans not in excess of 150 feet.
  Longer spans except when specifically designated, may be employed without increasing the size of wire, provided the sags and conductor separations are so increased that the allowable working tensions and conductor clearances of this order are not violated.

 

Table 7

Minimum Allowable Conductor Sizes (150ft. span)

Loading and Construction grade

Material or Type of Conductor

Soft drawn copper

Hard-drawn copper

Standard Aluminum wire

Reinforced stranded Aluminum

Copper-covered steel or

Galvanized iron or steel wire

A.W.G

A.W.G

A.W.G

A.W.G

A.W.G

 

Heavy Loading, Grade A

No. 4

No. 6

No. 1

No. 4

No. 6

in diam. strand

Heavy Loading, Grade B

4

6

1

6

8

No. 9 Steel W.G.

Heavy Loading, Grade C

4

6

1

6

8

No. 9 Steel W.G.

Light Loading, Grade A

4

6

1

4

8

* in diam. strand

Light Loading, Grade B

6

6

1

6

8

No. 9 Steel W.G.

Light Loading, Grade C

6

8

1

6

40

No. 9 Steel W.G.

Other supply service drops

10

10

-------

-------

12

-------

Supply service drops crossing trolley wires

8

10

-------

-------

12

-------

All Loadings Grade F

-------

12

-------

-------

12

No. 14 Steel W.G.

All loadings of communication service drops, paired wires or bronze conductors

-------

14

-------

-------

17

-------

 

* Three-sixteenth-inch strand may be used upon special permission of the Railroad Commission

 

C.    Strength

 

(1)    Heavy Loading Districts: Conductors in Grade A construction and in spans exceeding 150 feet shall have a tensile strength not less than that of No. 4 A.W.G hard-drawn copper, and said conductors shall preferably be stranded.

 

(2)    Light Loading Districts: The following requirements apply for various grades of construction and span lengths.

Conductors of Grade A construction in spans not exceeding 300 feet in length shall have a tensile strength not less than No. 6 A.W.G. hard drawn copper.

Conductors of Grade B or C construction in spans not exceeding 150 feet in length shall have a tensile strength not less than No. 6 A.W.G. soft drawn copper.

Conductors of Grade B or C construction in spans not exceeding 150 feet in length shall have a tensile strength not less than No. 8 A.W.G. soft drawn copper, provided the voltage is less than 750.

 

(3)    Heavy or Light Loading Districts: Where signal or communication lines take Grade B or C classification other than at railroad crossings, a minimum size of No. 8 AWG hard-drawn copper or its equivalent in tensile strength may be used.  In crossing over supply cables where Grade C construction is required No. 10 A.W.G. hard drawn copper or its equivalent may be used in spans not exceeding 150 feet.

 

(4)    Conductors of Voltage Exceeding 17,000 Volts: Conductors of voltages exceeding 17,000 volts crossing conductors of less than 17,000 volts, crossing a public highway shall have a strength at least equal to No. 4 A.W.G. stranded hard-drawn copper.  In lieu of this conductors carrying more than 17,000 volts shall, at the point of crossing, be supported on poles of such height and so placed that under no circumstance can the conductor of over 17,000 volts, or fall within a distance of ten feet from the surface of any public highway.

 

(5)    Sags and Tensions: Conductor sags shall be such that under the assumed loading conditions the tension in the conductors shall not be more than one-half the breaking strength of the conductor, other than communication circuits.  The minimum allowable sags for conductors calculated on this basis are given in Appendix C.  The use of sags greater than allowable minimum may be desirable in order to reduce working tensions.  Where sags greater than those indicated are used adequate clearance shall be provided.  (See Rule 47.)  Where the minimum size pins are used the conductor tensions shall be limited to 2000 pounds when applying the double arm, pin and conductor fastening provisions of Rules 49.2 and 49.3.

 

(6)    Splices: Splices in line conductors shall be of equal or greater strength than the conductors in which they are made.

 

(7)    Service Drops

 

a)    Supply: The minimum sizes shall apply only where the span does not exceed 150 feet.  The minimum for supply lines of like voltage and grade shall apply when the service drop is in excess of 150 feet.  Supply service drops of 0-750 volts shall, in all cases, have an insulating covering equivalent to standard double braid weatherproofing.

 

b)     Communication: Communication service drops of No. 16 AWG paired copper wire may be used provided they do not cross over supply lines, trolley contact or feeder conductors or railways.

 

D.    Replacements (see Rule 44.2)

 

Note    This Rule was modified by Supplement 1.  To see the changes made by supplement 1 click here.  This page contains the wording of the rule prior to Supplement 1.