General Order 95

Detailed Construction Requirements for Supply Lines
(Class H, L and T Circuits)

54.9    Low Voltage Racks, 0 - 750 Volts (Conductors Less than 15 Inches from Centerline of Pole, But Not Less than 2–1/2 Inches from The Surface of Pole).

A.    General

Conductors of 0 - 750 volts may be attached to poles by means of vertical racks of insulators or individual supports in vertical rack configuration. Such construction is hereinafter termed “rack construction.” Where rack construction is employed, the following rules shall apply.

Note:    For low voltage extended rack construction (conductors 15 inches or more from centerline of pole, but not less than 3 inches from the surface of pole) see Rule 54.12 .

Note:    Revised January 21, 1992, by Resolution SU–10.

B.    Pole Arrangement and Clearance

(1)    Clearance from Poles: Conductors of 0 - 750 volts in rack construction may have clearances less than 15 inches from centerline and 3 inches from surface of pole, as specified in Table 1, Column D, Cases 8 and 9 , respectively, but shall have a clearance of not less than 2.5 inches from the surface of pole (for interpretation of this 2.5 inch clearance see Figure 54–20 ).

(2)    Conductor Arrangement: Not more than 7 conductors of not more than 2 circuits shall be attached to any pole in a continuous rack group. In a rack group the conductors shall be of one ownership and the vertical separations between line conductor attachments shall be uniform.

Conductors, both line and service drop, in rack configuration shall not be attached to more than 3 sides of any pole at the level of any one rack group. Climbing space in conjunction with these attachments shall be maintained as specified in Rule 54.9–F .

C.    Conductor Material

All conductors of a rack group in the same vertical plane shall be of the same material.

(1)    Urban Districts: Conductors in rack construction in urban districts shall have a covering not less than the equivalent of weather–resistant covering.

(2)    Rural Districts: Line conductors in rack construction in rural districts may be bare conductors provided the vertical separation between conductors is not less than 12 inches and conforms to the requirements of Rule 54.9–D where greater separation is specified

D.    Conductor Spacing and Span Length

The vertical separation between conductors supported as a group in rack construction shall be not less than the following for span lengths as indicated:

E.    Vertical Clearance between Conductor Levels

A vertical clearance of not less than 6 feet shall be maintained between the top conductor supported in rack construction at one level and conductors supported on the same pole at the next level above except as provided in Rule 54.4–C6 for lead wires and as modified below:

(1)    With Guard Arm below Conductors of 750 - 22,500 Volts: The vertical clearance between the top conductor in a rack group and conductors of 750 - 22,500 volts at the next conductor level above, may be less than 6 feet but shall not be less than 4 feet. If a clearance of less than 6 feet is used, all of the following requirements shall be met:

a)    In tangent construction, a guard arm shall be installed directly above and approximately parallel to the top line conductor of such a rack group. Service drop conductors supported on a rack with the guard arm installed directly above and approximately parallel to the top line conductor of a rack group shall not pass between the surface of pole and the vertical plane of the line conductors.

b)    In deadend construction, the guard arm shall be placed above the rack at a right angle to the line conductor, provided that no service drop conductor attached to a rack so guarded makes a horizontal angle greater than 90 degrees with the vertical plane of the line conductors.

c)    Conductors in such a rack group, which are so guarded shall not be attached to more than one side of any pole.
  

d)    Any service drop conductors attached to and supported by the line conductors shall have a clearance of not less than 15 inches from surface of pole (see Figure 54–21 ).

Note:    Revised March 29, 1966 by Decision No. 70489; August 9, 1966 by Decision No. 71094,   September 18, 1967 by Decision No. 72984 and October 9, 1996 by Resolution SU–40.

(2)    Conductors Deadended Under Equipment: No guard arm will be required over conductors in rack configuration deadended on the surface of a pole directly below equipment (e.g., transformer, capacitor and other similar apparatus). Such conductors shall have a vertical clearance of not less than:

a)    4 Feet below unprotected line conductors; and

b)    As specified in Rule 54.4–C6 below the lowest point of the drip loop of the primary leads to the transformer(s); and

c)    10 Inches below the lowest part of the equipment case(s) or hanger(s).

(See Figure 54–22 )

(3)    Related Rack and Crossarm or Extended Rack: Where conductors supported in rack construction are connected to conductors supported on a crossarm or extended rack on the same pole, the vertical clearance between the level of conductors of 0 - 750 volts on the crossarm or extended rack and the nearest conductor in rack construction shall not be less than 2 feet and climbing space shall be maintained in the same quadrant or on the same side of pole through both conductor levels in accordance with climbing space requirements in Rules 54.7 and 54.9–F . This provision is not applicable where the crossarm is a combination arm.

(4)    Multiconductor Cable with a Bare Neutral: Multiconductor Cable with a Bare Neutral. 0 - 750 volts (Rule 54.10 ) may be installed with a  minimum vertical separation above or below conductors in rack configuration of 10 inches for spans not to exceed 200 feet and 12 inches for spans in excess of 200 feet.

EXCEPTION:    When rack construction is present, the most stringent climbing space requirements of Rule 54.9–F shall be maintained through both levels.

F.    Climbing Space in Rack Construction (See Figure 54–23 )

Climbing space shall be maintained through the levels of conductors supported in rack construction, for a vertical distance of not less than 4 feet above the top conductor and not less than 4 feet below the bottom conductor so supported. Where conductors in rack construction are installed at pole top, the climbing space shall extend up to the level of the lowest conductor of the rack group, and need not be provided through and above such levels.

The width of the climbing space measured horizontally through the centerline of the pole shall not be less than 5 inches plus the diameter of the pole and the extremities of such width shall be equidistant from the centerline of pole. The depth of the climbing space shall not be less than 30 inches measured perpendicularly to this climbing space boundary through the centerline of pole. The width of the climbing space, perpendicular to and at the extremity of this 30 inch–depth dimension, shall not be less than 38 inches and neither of the other two side boundaries shall make an angle of less than 90 degrees with the boundary through the centerline of pole (see Figure 54–23 .)

The position of the climbing space through the levels of conductors in rack construction shall be related to climbing spaces through the levels of conductors on crossarms in accordance with the requirements of Rule 54.7–A , Extended Rack Rule 54.12–F and Multiconductor Cable with Bare Neutral Rule 54.10–F . The climbing spaces through the levels of conductors of two or more rack groups which are separated less than 6 feet shall be maintained in the same quadrant or on the same side of pole.

Guys, vertical conductors attached to the surfaces of poles, and terminals are not permitted in climbing spaces through conductors in rack construction.

Note:    Revised October 9, 1996 by Resolution SU–40.