General Order 95

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

54.4    Clearances

Allowable variations in clearances due to side swing of suspension insulators, temperature, loading, etc., are given in Rules 37 and 38.

A.    Above Ground

The minimum vertical clearances shall be those specified in Rule 37 , Table 1 , with the following modifications:

(1)    Across Arid or Mountainous Areas: Across arid or mountainous areas supply circuits carrying 22,500 - 30,000 volts, inclusive, may have a clearance of less than 30 feet (Table 1, Case 4, Column F ) but not less than 25 feet above ground subject to a reduction of not more than 10 percent because of temperature and loading as specified in Rule 43 . Upon special permission from this Commission, a minimum clearance of 25 feet above ground may be applied in similar areas to circuits in excess of 30,000 volts, however, not including Class E circuits. For circuits in excess of 30,000 volts, no reduction of the 25 feet will be permitted for conditions less than maximum loadings or temperature specified in Rules 43.1 and 43.2 .

Note:    Revised March 29, 1966 by Decision No. 70489; August 9, 1966 by Decision No. 71094; and March 30, 1968 by Decision No. 73813.

(2)    Lead Wires for Transformers: Transformer lead wires shall have clearances above ground as specified in Table 1 except as modified by the provisions of Rule 58.1–B .

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

(3)    Over Swimming Pools: (See Figure 54–1 ) Installations of conductors, s ervice drops and guys over swimming pools shall be avoided where practicable. Where line conductors, service drop conductors or guys are installed over swimming pools the following rules apply:

a)    Line Conductors: Where unpr otected line conductors are installed over a swimming pool they shall have radial clearances from the top edge of the swimming pool walls and vertical clearances above the highest water level of the pool surface not less than the following:

1)    0 - 750 Volts - - 20 feet

2)    750 - 22,500 Volts - - 25 feet

3)    22.5 - 300 kV - - 30 feet

(See Table 1, Case 3, Columns D, E and F )

b)    Service Drops 0 - 750 Volts: Where service drop con ductors are installed over a swimming pool:

1)    Phase conductors shall be suitably insulated (see Rule 20.9–G ).

2)    Vertical clearances above the highest water level of the pool surface and radial clearances from the top edge of the pool wall shall be:

a)    16 feet for public and commercially operated pools.

b)    12 feet for residential pools.

3)    No service drop may be installed less than 16 feet vertically above the horizontal plane through a diving board or platform, such plane being the area within 8 feet radially of the diving board or platform that is over the water surface of the pool.

4)    No service drop may be installed less than 12 feet vertically above the horizontal plane through a diving board or platform, such plane being the area within 3 feet radially of the diving board or platform that is not over the water surface of the pool.

c)    Ungrounded Portions of Guys:

1)    Shall have radial clearances from the top edge of the swimming pool wall of not less than 18 feet.

2)    Shall have vertical clearances above the highest water level of the pool surface of not less than 18 feet.

3)    Shall not be installed less than 18 feet vertically above the horizontal plane through a diving board or platform, such plane being the area within 8 feet radially of the diving board or platform that is over the water surface of the pool.

4)    Shall not be installed less than 12 feet vertically above the horizontal plane through a diving board or platform, such plane being the area within 6 feet radially of the diving board or platform that is not over the water surface of the pool.

d)    Grounded Portions of Guys:

1)    Shall have vertical clearances above the highest water level of the pool surface of not less than 16 feet.

2)    Shall not be installed less than 16 feet vertically above the horizontal plane through a diving board or platform, such plane being the area within 8 feet radially of the diving board or platform that is over the water surface of the pool.

3)    Shall not be installed less than 8 feet vertically above the horizontal plane through a diving board or platform, such plane being the area within 3 feet radially of the diving board or platform that is not over the water surface of the pool.

Note:    Added January 2, 1962 by Resolution E–1109 and revised November 21, 1990 by Resolution No. SU–6.

B.    Above Railways and Trolley Lines

(1)    Which Transport Freight Cars: The clearances specified in Table 1, Case 1 , are based upon a maximum height of standard freight cars of 15 feet 6 inches from top of rail to top of running board. The clearance specified in Table 1, Case 1, Column C shall not be reduced because of temperature or loading. The clearance specified in Table 1, Case 1, Columns A, B, D, E and F , shall not be reduced more than 5% because of temperature or loading.

Note:    Revised February 1, 1948 by Supplement No. 1, Decision No. 41134, Case No. 4324.

(2)    Operated by Overhead Trolley: The clearances specified in Table, 1, Case 2, Columns D, E, and F are based upon a trolley pole throw of 26 feet, the usual maximum height of a free trolley pole above the top of rails or surface of streets used by trolley cars or coaches. Above trolley lines having a maximum trolley pole throw at variance of 26 feet, the specified clearances shall be increased or may be reduced accordingly provided that the clearances specified in Column F shall not be reduced to less than 30 feet and the clearances specified in Columns D and E shall not be reduced to less than 25 feet. See Rule 57.4–B2 for the clearances required for grounded cables and messengers.

Where railways operated by overhead trolley transport freight cars, the clearance requirements of Rule 54.4–B1 also apply.

C.    Between Conductors

The minimum allowable clearances between conductors are specified in Rule 38 , Table 2 , with the following modifications for supply conductors. (These modifications, like the tabular values, are also subject to the allowable variations specified in Rule 38 ):

(1)    On Different Crossarms on the Same Pole:

a)    Conductors of 750 - 7,500 volts: The 4 foot vertical clearance between conductors of 750 - 7,500 volts, as specified in Table 2, Case 10, Column E, may be reduced to not less than 2 feet provided all the following conditions are met:

The conductors involved are of one ownership and the circuits are operated and maintained by the same crews of workmen;

Under no conditions is this reduced clearance to be applied in new construction involving new poles;

Buck arm construction, transformers or capacitors are not involved;

More than one reduced clearance of 2 feet shall not be used on any pole; and

It is not practicable to obtain the normally required 4 foot clearance.

b)    Conductors of 7,500 - 20,000 volts: The 4 foot vertical clearance between conductors of 7,500 - 20,000 volts, as specified in Table 2, Case 11, Column F , may be reduced to not less than 3 feet, provided all of the following conditions are met:

The conductors involved are of one ownership and the circuits are operated and maintained by the same crews of workmen;

Under no condition is this reduced clearance to be applied in new construction involving new poles;

Buck arm construction, transformers or capacitors are not involved;

More than one reduced clearance of 3 feet shall not be used on any pole; and

It is not practicable to obtain the normally required 4 foot clearance.

c)    Triangular and Vertical Configuration on Different Crossarms on the Same Pole: When crossarms are used to support conductors of the same circuit at different levels (as in triangular or vertical configuration), the crossarms may be arranged so that the vertical separation of the conductors of the same circuit shall not be less than the pin spacings of Table 2, Case 15.

Where circuits are installed on crossarms in vertical or triangular configuration with vertical conductor separations less than as specified in Table 2, Cases 9 to 13 , not more than two circuits shall be installed on the same crossarms and the conductors of both circuits shall be arranged in identical physical configuration on opposite sides of the pole except at points of transposition. When different voltage classifications are involved, the vertical separation of the conductors shall not be less than the pin spacing for the higher voltage.

For pole–top triangular construction with crossarms involving a single circuit see Rule 54.4–D8.

For pole–top triangular and vertical construction without the use of wood crossarms see Rule 54.11 .

Note:    Revised May 22, 1990 by Resolution No. SU–5.

(2)    On Related Line and Buck Arms:

a)    One voltage Classification*: The clearances of Table 2, Case 14 (and clearances less than as specified in Cases 9 to 13 ) shall not be applied consecutively both above and below the same conductor. The foregoing provisions of this rule do not apply to conductors in triangular or vertical configuration, the clearances of Table 2, Case 14 being directly applicable.

Where conductors of one voltage classification only are supported on the same crossarms, the vertical clearances specified in Table 2, Case 14 , are not required between conductors on line arm and conductors on related buck arm provided no conductors on the line arm cross conductors of different phase or polarity on the buck arm.

*Voltage classifications for this purpose are:

Note:    Revised March 30, 1968 by Decision No. 73813.

b)    Combination Arms: Where conductors of 0 - 750 volts and conductors of 750 - 7,500 volts are supported on the same crossarms with the nearest conductors of the two classifications separated a horizontal distance of not less than 36 inches (plus any necessary vacant pin spaces required by Rule 54.7–A3c ) the vertical separation between conductors on such a line arm and conductors on a related buck arm shall be not less than 4 feet. This vertical separation may be less than 4 feet but not less than 2 feet provided the horizontal separation of conductors of the two classifications is not less than 42 inches (plus any necessary vacant pin spaces required by Rule 54.7–A3c ) and all conductors of the same voltage classification are supported on the same ends of the crossarms.

Where this vertical separation of 2 feet (or less than 4 feet but more than 2 feet) between conductors on a line arm and related buck arm is utilized, any conductor on such line or buckarm shall have a vertical clearance from any other conductor level of not less than clearances specified in Table 2, Cases 8 to 13 .

(3)    On the Same Crossarms:

a)    Different Voltage Classifications: Supply conductors of different voltage classifications may be supported on the same crossarms in conformity with the requirements of Rule 32.4 .

b)    On Brackets Attached to Crossarms: Line conductors supported on brackets or extensions attached to crossarms shall be maintained outside of the outer pin position on the crossarm with a radial separation not less than the minimum pin spacing specified in Table 2, Case 15 , from any other line conductors supported by the same arm. Line conductors supported on such brackets or crossarm extensions shall be of the same voltage classification as the conductors supported on the same side of pole by the crossarm to which the bracket or arm extension is attached. The vertical clearances specified in Table 2, Cases 1 to 14 shall be provided between the conductor on the bracket and the conductor level of any other conductors not supported on the crossarm to which the bracket is attached.

c)    Same Phase or Polarity: The clearances specified in Table 2, Cases 15 and 17 , are not required between conductors of both the same potential and the same phase or polarity.

(4)    Deadended on Pole in Vertical Configuration:

a)    Conductors of 750 Volts or Less: Where conductors of 750 volts or less are supported in vertical configuration directly on a pole without the use of crossarms, the requirements for rack construction, Rule 54.9 , shall apply.

b)    Conductors of More than 750 Volts Supported on Climbable Poles: Where conductors of more than 750 volts are supported in vertical configuration directly on a climbable pole without the use of crossarms at line terminations, angles or corners, the following requirements apply:

The vertical separation between conductors of the same circuit shall not be less than the clearances specified in Table 2, Cases 15 and 20;

The vertical separation of different circuits shall not be less than the clearances specified in Table 2, Cases 8 to 13 , inclusive;

Not more than four conductors of a circuit of more than 750 volts shall be supported directly on a pole in vertical configuration without the use of crossarms. Branch circuits may be taken from such construction without the use of crossarms provided a climbing and working space as specified in Rule 54.7 and 54.11 is maintained; and

The clearance of conductors from surface of pole shall not be less than as specified in Rule 54.4–D6b .

See Rule 54.11–F for climbing space requirements for conductors dead ended on poles in vertical configuration.

Note:    Revised February 7, 1964 by Decision No. 66707; January 6, 1968 by Decision No. 73455; and January 21, 1992, by Resolution SU–10.

c)    Conductors of More than 750 Volts Supported on Nonclimbable Poles: Where conductors of more than 750 volts are supported in vertical configuration on nonclimbable poles in partial underground distribution at line terminations, angles, or corners, the following requirements apply:

Not more than four conductors of a single circuit of 750 - 22,500 volts shall be supported directly on the pole in vertical configuration without the use of crossarms. Branch circuits may be taken from such construction without the use of crossarms provided that conductors are supported on not more than three sides of the pole, there being four sides;

The vertical separation between conductors shall not be less than the pin spacings specified in Table 2, Case 15 ; and

The clearance of conductors from surface of pole shall not be less than as specified in Rule 54.4–D2 .

Note:    Added February 7, 1964 by Decision No. 66707; Amended March 29, 1966 by Decision No.70489; Revised August 9, 1966 by Decision No. 71094 and November 21, 1990 by Resolution No. SU–6.

(5)    Rack Construction (See Rule 54.9 )

Extended Rack Construction (See Rule 54.12 )

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

(6)    From Lead Wires and Drip Loops to Other Conductors:

The vertical clearances between the lowest point of lead wires (to conduit runs, transformers or other equipment), excepting drop wires to street lights, and the next supply conductor level below such lead wires may be less than the clearances specified in Table 2, Cases 9 to 12, Columns D, E, F and G, provided the vertical separation is maintained as great as practicable and in no case less than the following (see Figure 54–22 ):

(7)    Vertically at Crossings in Spans:

The Vertical clearance required at crossings in spans by Table 2, Cases 4, 5, 6 and 7 , may be reduced when:

1)    All conductors are of the same circuit, and

2)    Vertical taps are installed between related crossing conductors.

The minimum vertical clearance shall be the following:

EXCEPTIONS:

a)    In vertical configuration, there is no specific vertical clearance required between conductors that are mechanically and electrically connected at the crossing.
 

b)    There is no specific clearance required for 0 - 750 volt multiconductor cable having a bare neutral (Rule 54.10 ) provided the messengers are mechanically connected.

Note:    Rule 54.4–C7 deleted March 30, 1967 by Decision No. 73813. Added again on November 6, 1992 by Resolution SU–15.

D.    From Poles

The basic minimum clearances of conductors from centerline and surface of poles are specified in Table 1, Cases 8 and 9. Modifications of these basic clearances are specified in Rule 37 and by the following provisions:

(1)    Center Line Clearance at Angles in Lines: The clearance specified in Table 1, Case 8 may be reduced at angles in lines where it is necessary to support conductors on the side of insulators placed on pole–pins, provided the distance between the center of any such pole–pin and the centerline of the crossarm through bolt is not less than the distance specified in Table 1, Case 8 . This Rule 54.4–D1 shall not be held to permit any greater reduction of climbing space widths than that specified in Rule 54.7–A for line angles.

Note:    Revised May 22, 1990, by Resolution SU–5.

(2)    Center Line Clearances for 750 Volts and above: The clearances referred to in Table 1, Case 8, Columns E and F , apply as follows with respect to voltage:

These clearances from centerline of pole need not apply to conductors of 750 - 7,500 volts and 7,500 - 22,500 volts supported in vertical configuration in partial underground distribution provided: a) such conductors have clearances from surface of pole of not less than 6 inches, b) in tangent construction, conductors so supported are not attached to more than one side of pole, and c) in deadend construction conductors so supported are not attached to more than three sides of a pole (there being four sides, see Figure 54-3 ).

Note:    Revised February 7, 1964 by Decision No. 66707; March 29, 1966 by Decision No. 70489 and August 9, 1966 by Decision No. 71094.

(3)    Conductors Passing and Unattached: The centerline clearance between poles and conductors which pass unattached shall be not less than 1–1/2 times the clearance specified in Table 1, Case 8 , except where the interset pole is within 10 feet of a pole to which the passing conductors are attached or where the provisions of Table 1, Case 10, Columns D, E, F, and G can be applied. Where poles of the two lines are less than 10 feet apart, clearances not less than as specified in Table 1, Case 8 , shall be maintained between the center line of any pole and conductors which pass unattached.

Note:    Revised January 8, 1980 by Decision No. 91186.

This rule will often necessitate the use of clearance crossarms with conductor clearances as specified in Table 1, Case 8 , or the alternate increased clearances for service drops as provided in Rule 54.8–C3 .

(4)    Longitudinal Cables and Messengers: Messengers and longitudinal supply cables, treated as required in Rule 57.4–F , may be attached to the surface of pole and thus have clearances less than as specified in Table 1, Cases 8 and 9, Column D.

(5)    Rack Construction for 0 - 750 Volts: Conductors of 0 - 750 volts in rack construction may be attached to poles with clearances less than 15 inches and 3 inches as specified in Table 1, Cases 8 and 9 respectively, provided such construction complies with the provisions of Rule 54.9 and such conductors, not including their tie wires, shall have a clearance of not less than 2 1/2 inches from surface of pole.

(6)    Deadended on Pole:

a)    0 - 750 Volts: Where conductors of 0 - 750 volts are dead ended on a pole in vertical configuration, the clearances specified for rack construction, Rule 54.9–B1 , shall apply.

b)    More than 750 Volts Supported on Climbable Poles: Where conductors are supported on a climbable pole in vertical configuration, the energized portions of such conductors shall have clearances of not less than 15 inches from the surface of the pole for voltages between 750 and 7,500 volts and 18 inches from the surface of pole for voltages in excess of 7,500 volts.

Not more than four conductors of a circuit of more than 750 volts shall be attached directly to a pole in vertical configuration without the use of crossarms. Branch circuits may be taken from such construction without the use of crossarms provided a climbing and working space as specified in Rules 54.7 and 54.11 is maintained.

Note:    Revised February 7, 1964 by Decision No. 66707; January 6, 1968 by Decision No. 73455; July 22, 1968 by Decision No. 74342;and January 21, 1992, by Resolution SU–10.

c)    More than 750 Volts Supported on Nonclimbable Poles: Where conductors are deadended on a nonclimbable pole in partial underground distribution, the energized portions of such conductors shall be not less than 6 inches from surface of pole (see Rule 54.4–D2 ).

Note:    Added February 7, 1964 by Decision No. 66707.

(7)    This space is intentionally left blank.

Note:    Rule 54.4–D(7) was deleted March 9, 1988 by Resolution No. E–3076. Subsequent Rules 54.4–D8 and 9 are not renumbered.

(8)    At Top of Pole:

Clearance between a Single Conductor and Center Line of Pole: A single conductor of a circuit may be attached directly to the top of a pole or to a crossarm at the top of a pole at a distance less than as specified in Table 1, Case 8 . Where a transformer(s) or similar apparatus is connected to a circuit so arranged, a vertical clearance of not less than 30 inches shall be maintained between its unenergized metal parts and the lowest primary line conductor of the circuit directly above.
For pole–top triangular and vertical construction without the use of wood crossarms see Rule 54.11 .

Note:    Revised March 29, 1966 by Decision No. 70489; August 9, 1966 by Decision No. 71094;March 9, 1988 by Resolution E–3076, May 22, 1990 by Resolution SU–5 and October 9, 1996 by Resolution SU–40.

(9)    Lateral and Vertical Conductors: Unprotected lateral and vertical conductors (excepting ground wires installed as specified in Rule 54.6–B , bond wires installed as specified in Rule 53.4 , and suitable insulated conductors of 0 - 750 volts entering terminal fittings mounted on the surface of poles as specified in Rule 54.6–F ) shall not be attached to the surface of poles, but shall be supported on crossarms or other supports and arranged to maintain the specified clearances from poles, towers or structures and other conductors ( Table 1, Cases 8 and 9, and Table 2, Cases 15, 16 and 17 ), and to maintain the climbing and working spaces as required in Rule 54.7 . In lieu of the foregoing, lateral and vertical conductors may be installed on the surface of poles provided the conductors are suitably insulated and protected as specified in Rule 54.6 .

E.    From Crossarms

The minimum distances of unprotected conductors from the surface of crossarms are specified in Table 1, Case 9. These clearances from the surface of crossarms are not required for suitably insulated conductors in runs which are protected as specified in Rule 54.6–C or for suitably insulated conductors where entering such protected runs.

Lead wires of 0 - 5,000 volts may be less than 3 inches, but shall be not less than 1 inch, from the surface of crossarms where equipment (cutouts, switches, etc.) mounted on the crossarms is so constructed that clearances of less than 3 inches are necessary for the entrance of such leads to the equipment.

F.    From Guys and Messengers (See Table 2, Column A , Rule 56.4–C and Rule 57.4 )

G.    From Grounded Metal Boxes, Hardware and Equipment

All grounded metal boxes, hardware and grounded metal cases for equipment, on non–metallic poles or non–metallic structures shall be a minimum of 36 inches above and 30 inches below the next level of unprotected conductors. Such equipment shall have a minimum clearance of 48 inches above or 72 inches below communication line conductors, cables and messengers of different ownership. See Figure 54–4 .

EXCEPTIONS:

(1)    0 - 750 volt line conductors (not including incidental pole wiring, e.g. jumpers) a 10 inch radial clearance is required.
   

(2)    Equipment (e.g. in Rule 58.6) operated at 0 - 750 volts and mounted not less than 15 inches from the surface of the pole. These clearances shall not be less than the radial clearances required for incidental pole wiring by Table 2, Cases 16 and 17 .
 

(3)    Grounded portions of risers and their associated terminal fittings, brackets and hardware. These clearances shall not be less than the radial clearances required for incidental pole wiring by Table 2, Cases 16 and 17 .
   

(4)    Lightning arresters, grounded insulator pins and insulators with grounded bases and their associated supports. These clearances shall not be less than the radial clearances required for incidental pole wiring by Table 2, Cases 16 and 17 .
   

(5)    The 72 inches may be reduced to not less than 48 inches where a communication cable does not have a pole mounted drop distribution terminal located above the grounded metal box, hardware or metal case for equipment, or where the grounded metal box, hardware or metal case for equipment is securely bonded to the communication cable and/or messenger.
   

(6)    The 72 inches may also be reduced to 48 inches when the grounded metal box, hardware or metal case for equipment is on the opposite side of a pole from a pole mounted communication drop distribution terminal.

Any item grounded in accordance with this rule shall be effectively grounded (see Rule 33.3 ).

Note:    Revised January 19, 1994 by Resolution SU–25 and October 9, 1996 by Resolution SU–40.

H.    Above, alongside, or in Immediate Proximity to Buildings, Bridges and Other Structures

(1)    Unattached Conductors: Conductors should be arranged so as not to hamper or endanger workers and firefighters while performing their duties. The basic clearances of conductors from buildings are specified in Table 1, Cases 6 and 7 . The horizontal clearance ( Table 1, Case 7 ) shall be maintained until the vertical clearance ( Table 1, Case 6 ) is attained (see Figure 54–24 ). The requirements of Table 1, Case 7 , also apply at fire escapes, exits, windows, etc., at which human contact may be reasonably expected.

EXCEPTION:    The horizontal conductor clearance from buildings may be reduced from 6 feet to 4 feet ( Table 1, Case 7, Column E ) if all of the following criteria are met:

a)    The conductor voltage is 7,500 volts or less; and

b)    The conductor vertical clearance above ground is more than 35 feet; and

c)    The building height next to the conductors exceeds the conductor height by 6 feet or more; and

d)    There are no fire escapes, exits, or windows at which human contact may be reasonably expected.

Note:    See Rule 54.8–B4 for service drop clearance requirements and Table 58–1 for special treatment of bus and lead wires of transformer installations in alleys.

(2)    Attached Conductors: Unprotected conductors not exceeding 22,500 volts may be supported by attachments to buildings, bridges and other structures. To conductors of 0 - 750 volts so supported, the clearances of Table 1, Case 7, Columns B, C and D shall apply. To conductors of 750 - 22,500 volts so supported a minimum horizontal clearance of 8 feet shall apply.

In lieu of these requirements for unprotected conductors, supply conductors may be installed on the surface of buildings, bridges and other structures in grounded metal conduit or other grounded sheath or grounded shield suitably protected from mechanical injury.

Note:    Revised March 29, 1966 by Decision No. 70489; August 9, 1966 by Decision No. 71094; November 6, 1992 by Resolution SU–15 and January 19,1994 by Resolution SU–25.

I.    Below, alongside, through or in Immediate Proximity to Bridges, Viaducts or Similar Structures

Unprotected supply conductors which pass unattached below or in immediate proximity to bridges, viaducts or similar structures shall be maintained at clearances above ground and walkways as specified in Table 1, Cases 1 to 6 inclusive; at clearances from walls and underneath parts of such structures as specified in Table 1, Case 7 ; and at clearances from conductors of other classifications as specified in Table 2, Case 3 . The horizontal clearance ( Table 1, Case 7 ) shall be maintained until the vertical clearance ( Table 1, Case 6 ) is attained (see Figure 54–24 ).

Conductors of 0 - 22,500 volts, passing under or through bridges, viaducts or similar structures may be attached thereto in accordance with the provisions of Rule 54.4–H2 . Warning signs of a substantial character with letters not less than 3 inches in height reading “High Voltage” for voltages in excess of 750 volts shall be placed conspicuously on each crossarm or structural member supporting the conductors.

In lieu of these requirements for unprotected conductors, supply conductors which cross below bridges, viaducts or similar structures shall be enclosed in grounded metal conduit or in other effectively grounded sheath or grounded shield suitably protected from mechanical injury.

Note:    Revised March 29, 1966 by Decision No. 70489 and August 9, 1966 by Decision No. 71094 and November 6, 1992 by Resolution SU–15.