Original General Order 95

Section V

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 20,000-30,000 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 per cent because of temperature and loading as specified in Rule 43.  Upon special permission from the Rail Road Commission, a minimum clearance of 25 feet above ground may be applied in similar areas to circuits in excess of 30,000 volts, in which case 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.

(2)    In Rural Districts, Conductors of 750-20,000 Volts:

a)    Crossing Roads or Driveways: In rural districts the minimum clearance of 25 feet specified in Table 1, Case 3 Column E may be reduced to 22 feet above ground for conductors crossing or overhanging traversable portions of public or private roads or driveways.  This modified minimum clearance of 22 feet shall in no case be reduced because of temperature or loading at conditions less than the maximum loading or temperature specified in Rules 43.1 and 43.2.

b)    Above Agricultural Areas Along Roads:  In rural districts the minimum clearance of 25 feet specified in Table 1, Case 4 Column E may be reduced to 18 feet above ground lines across areas capable of being traversed by agricultural equipment and along roads where no part of the line overhangs any traversable portion of a public or private roadway.  This modified minimum clearance of 18 feet shall in no case be reduced because of temperature or loading at conditions less than maximum loadings or temperature specified in Rules 43.1 and 43.2.  Care should be exercised in using this minimum clearance along roads, above or along ditches where mechanical devices are used for maintenance, near trees in orchards, near trees or structures which can be climbed and in other similar situations.

(3)    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 58.3-B1a.

B.    Above Railways and Trolley Lines

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

(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 to 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 Column 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 750-7500 volts: The 4 foot vertical clearance between conductors of 750-7500 volts, as specified in Table 2, Case 10, Column E, may be reduced to not less than 2 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 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 750-20,000 Volts: The 4 foot vertical clearance between conductors of 7500-20,000 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 conditions is the 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: Crossarms used to support conductors of a circuit at different levels (as in triangular or vertical configuration) need not be spaced as in Table 2, Cases 9 to 13, but may be arranged so that the vertical separation of conductors of the same circuit shall be not less than the pin spacing of Table 2, Case 15

Rule 54.4-D8 applies for pole-top triangular construction involving one circuit.

Where circuits are installed 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 pole except at points of transportation.  In the event different voltage classifications are involved, the vertical separation of the conductors shall be not less than the pin spacing for the highest voltage concerned.

(2)    On Related Line and Buck Arms:

a)    One Voltage Classification*: The clearance 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 arms.

b)    Combination Arms: Where conductors of 0-750 volts and conductors of 750-7500 volts are supported on the same crossarm with the nearest conductors of the two classifications 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 buck arm 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 the pole by the crossarm to which the bracket or arm extensions 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)    Dead Ended 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 the rack construction, Rule 54.9, shall apply.

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

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

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

Not more than two conductors of a circuit of 750-5000 volts shall be supported directly on a pole in vertical configuration without the use of crossarms.  The number of conductors of a circuit of more than 5000 volts so supported is not limited.  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 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 54.7-A1 for climbing space requirements for conductors dead ended on poles in vertical configuration.

(5)    Rack Construction: See Rule 54.9

(6)    From Lead Wires and Drip Loops to Other Conductors: The vertical clearances between 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:

(7)    Voltages of More Than 68,000 Volts:

a)    Crossing or Colinear with Wires or Cables of Other Lines:  The clearances specified in Table 2, Column I, Cases 1 to 7 inclusive, for conductors of more than 68,000 volts crossing or collinear with conductors, guys and messengers which are not supported on the same poles, shall be increased by ˝ inch for each kilovolt above 68kv.

b)    Supported on the same Structure: The vertical separation between conductors on line arms and conductors on line arms and conductors on related buck arms (Table 2, Column I, Case 14) and the horizontal separation of conductors on crossarms (Table 2, Column I, Case 15) shall be increased ˝ inch for each kilovolt above 68kv.

D.    From Poles

The basic minimum clearances of conductors from center line 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 clearances 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 center line 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-A2 for line angles.

(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.

(3)    Conductors Passing and Unattached: The centerline clearance between poles and conductors which pass unattached shall not be less than 1 ˝ times the clearances specified in Table 1, Case 8, except where the interest pole is within 10 feet of a pole to which the passing conductors are attached.  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.

This rule will often necessitate the use of clearance crossarms with conductor clearance 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 ˝ inches from surface of pole.

(6)    Dead Ended on Poles:

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:  Where conductors are dead ended on a pole in vertical configuration, the energized portions of such conductors shall have clearances of not less than 15 inches from the surface of pole for voltages between 750 and 7500 volts and 18 inches from the surface of pole for voltages in excess of 7500 volts.  Where conductors of more than one circuit are dead ended on a pole in vertical configuration, increased pole clearances are required as follows:

All energized portions of conductors of a circuit dead ended in vertical configuration below any other circuit on a pole shall be maintained at a clearance of not less than 3 feet from the surface of the pole for conductors of more than 7500 volts; and

Not more than two conductors of a circuit of 750-5000 volts shall be attached directly to a pole in vertical configuration without the use of crossarms.  The number of conductors of a circuit of more than 5000 volts so supported on a pole is not limited.  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 is maintained.

(7)    Dead Ended in Horizontal Configuration:

a)    0-7500 Volts (see App. G, Figs 13 and 14): A conductor of a circuit of 0-7500 Volts in horizontal configuration on a crossarm may be dead ended (at conductor terminations, angles, corners and for change in conductor size) in line with the center line of pole or in line with a distance from center line of pole less than 15 inches specified in Table 1, Case 8 provided:

Where the circuit concerned is supported on a line arm only (with no related buck arm present) a conductor is so dead ended in one direction only with climbing space maintained on the opposite side of the pole and with the energized portions of the conductor so dead ended maintained at a clearance of not less than 20 inches from center line of pole;

In corner construction a conductor is so dead ended in one direction only from the line arm and one direction only from the buck arm with the energized portions of conductors so dead ended maintained at a clearance of not less than 30 inches from the surface of the pole and required climbing space maintained (see Rule 54.7); and

Where a conductor is so dead ended with a line arm and related buck arm present, no transformer or other apparatus carried on the pole is connected to the circuit concerned.

b)    More than 7500 Volts (see App. G, Fig 14): A conductor of a circuit of more than 7500 volts in horizontal configuration on a crossarm may be dead ended (at conductor terminations, angles, corners and for change in conductor size) in line with the center line of pole or in line with a distance from center line of pole less than 18 inches specified in Table 1, Case 8 provided:

Where the circuit concerned is supported on a line arm only, except at the top of a pole under the provisions of Rule 54.4-D8b, a conductor is so dead ended in one direction only with climbing space maintained on the opposite side of the pole and with the energized portions of the conductor so dead ended maintained at a clearance of not less than 24 inches from the center line of pole;

In corner construction a conductor is so dead ended in one direction only from the line arm and one direction only from the buck arm with the energized portions of conductors so dead ended maintained at a clearance of not less than 30 inches from the surface of the pole and required climbing space maintained (see Rule 54.7); and

Where a conductor is so dead ended with a line arm and related buck arm present, no transformer or other apparatus carried on the pole is connected to the circuit concerned.

(8)    At Top of Pole:

a)    0-7500 Volts in Triangular Configuration: A single conductor of a circuit of 0-7500 volts may be attached at the top of the pole provided the other conductors of the same circuit are on a crossarm and are not less than 2 feet vertically below the level of such single conductor, except that such a 2-foot vertical separation is not required for dead-ended conductors conforming to provisions of Rule 54.4-D7a.

Where this triangular configuration is used, all conductors of other circuits on crossarms on the pole shall be not less than 4 feet below the level of the lower conductors of the pole-top circuit and conductors of 0-750 volts in rack construction shall conform to the requirements of Rule 54.9-E.

b)    More than 7500 Volts: A single conductor of a circuit of more than 7500 volts 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, provided no transformer or other apparatus (excepting pole-top switches or lighting arresters) carried on the pole is connected to the circuit so arranged.

Where this construction is used, all conductors of other circuits on the pole shall be not less than 6 feet below the pole-top conductor except that in rural districts the conductors of a 0-750 volt secondary circuit may be not less than 4 feet below the conductor level of such a primary circuit by means of which the secondary is supplied.

Dead ending of a conductor at top of pole under these provisions is optional with dead ending under the requirements of Rule 54.4-D7b.

(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 suitably 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 arranges 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 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 0-5000 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 and Equipment

On Wood poles or structures, all grounded metal boxes and grounded metal cases for equipment shall not be less than 3 feet above or 6 feet below the level of unprotected supply conductors, excepting street light drop wires which are not less than the distances specified in Rule 92.1-F5 from the messengers, conductors or metal boxes therein mentioned.  Where it is impracticable to obtain a clearance of at least 6 feet below unprotected supply conductors of 750 volts or less, a clearance of not less than 4 feet below such conductors will be permitted if a protective covering or guard is provided above such metal box or case.

This requirement does not apply to bends and terminals of risers or runs , which shall be treated as specified in Rule 54.6-F, nor to certain transformer cases as provided in Rule 58.3-C3, nor to the cases of oil switches treated as specified in Rule 52.7-F2.

Metal Conduit boxes and fittings of runs or risers shall be treated in accordance with the provisions of Rules 54.6-D, E and F.

H.    Above or Along the Sides of Buildings, Bridges and Other Structures

(1)    Unattached Conductors: Conductors shall be so arranged as to hamper and endanger fireman and workmen as little as possible in the performance of their duties.  The basic clearances of conductors from buildings are specified in Table 1, Cases 6 and 7.  The requirements of Table 1, Cases 7 also apply at fire escapes, exits, windows, etc., at which human contact may be expected.

Where the vertical distance above ground of conductors of 7500 volts less is in excess of 35 feet, the horizontal clearances front eh buildings may be less than 6 feet (Table 1, Case 7, Column E) but shall be not less than 4 feet.  See Rule 54.8-B4 for service drop clearance requirements.

For special treatment of bus and lead wires of transformer installations in alleys, etc., see Rule 58.3-B2.

(2)    Attached Conductors: Unprotected conductors not exceeding 20,000 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 750-20,000 volts so supported a minimum horizontal clearance of 8 feet shall apply.

In lieu of theses requirements for unprotected conductors, supply conductors may 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.

I.    Under or Through Bridges, Viaducts or Similar Structures

Unprotected supply conductors which pass unattached under bridges, viaducts or other structures shall be maintained at clearances above ground and walkways as specified in Table 1, Cases 1 to 6 incl.; 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.

Conductors of 0-20,000 volts, passing under or through bridges, viaducts or similar structures, may be attached thereto in accordance with the provision 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 under bridges, viaducts or other structures shall be enclosed in grounded metal conduit or in other effectively grounded sheath or grounded shield suitably protected from mechanical injury.