Change List for this Rule

 

General Order 95

 

Section VIII

 

Detailed Construction Requirements for Communication Lines
(Class C Circuits)

 

87.4    Clearances

 

The clearances for conductors as specified in Rule 84.4 shall apply to cables and their messengers except where modified herein and shall be measured to the nearest surfaces of the cable and messenger assembly, including cable rings and messenger supports.

 

A.    Above Ground (See Rule 84.4–A )

 

B.    Above Railways and Trolley Lines

 

(1)    Which Transport Freight Cars (See Rule 84.4–B1 )

 

(2)    Operated by Overhead Trolley:

The clearances specified in Table 1, Case 2, Columns A and B are based upon a maximum trolley pole throw of 26 feet.

Messengers and cables may have clearances above the rails or running surfaces used by trolley cars or coaches less than the distance specified in
Table 1, Case 2, Columns A and B (26 feet) for trolley–throw clearance, provided the messengers and cables are not less than 4 feet above the trolley contact conductor and are encased in wood boxing or moulding 7/8 inch or more in thickness for distances of at least 2 feet horizontally from the vertical plane of each trolley contact conductor.

Where railways operated by overhead trolleys transport freight cars, the provisions of
Rule 84.4–B1 also apply.

 

C.    Between Conductors and Cables

The minimum horizontal and vertical clearances shall be those specified in
Rule 38 , Table 2 (see also, Rule 32.2–D ) with the following modifications.

 

(1)    Cable Conductors: Insulated cables (including rubber–insulated single conductors, duplex, triplex, and paired conductors, whether single or grouped, and whether with or without supporting messengers) are treated as single conductors, and therefore no specified clearance is required between the individual conductors which comprise them. The clearance of 3 inches required by Table 2, Case 15, Column C, likewise does not apply between different cables.

 

(2)    Between Separate Cables: The horizontal separation of 3 inches specified in Table 2, Case 15, Column C , is not intended to apply between separate cables on crossarms.

 

(3)    Attached to Poles: On poles which carry no supply conductors or crossarms, communication cables or messengers may be attached to the sides of poles in any position within 3 feet of the top of the pole provided metal–sheathed cables or messengers are separated from open wire conductors in this section of the pole by a vertical distance of not less than 12 inches.

On poles where communication conductors are supported on crossarms and no supply conductors (except supply service drop clearance attachments) are attached, apply the provisions of
Rule 84.4–D1 and Figure 84–2 .

Cables or messengers where attached to the surface of poles which support supply conductors, shall not be less than 6 feet vertically below the level of supply conductors.

 

EXCEPTION:    This minimum clearance of 6 feet may be reduced to not less than 4 feet below supply conductors of 0 - 750 volts provided a guard arm is placed above the messenger and cable (or self–supporting cable) in accordance with the provision of Rule 87.7–B (see Rule 21.0–D for guard arm definition). No cable or messenger shall be attached to the surface of such a pole less than 2 feet below the lowest level of communication conductors on crossarms unless a minimum horizontal separation of 30 inches is maintained between the messenger or cable and the communication conductors on the opposite side of pole.

Note:    Revised November 21, 1990 by Resolution SU–6.

 

D.    From Poles

 

(1)    Cables or Messengers Supported on Crossarms: Cables on messengers supported on crossarms shall have a clearance of not less than 15 inches from the center line of poles which support supply conductors.

Cables or messengers supported on crossarms shall have a clearance of not less than 9 inches from the center line of poles which support only communication conductors.

 

(2)    Cables or Messengers Not Supported on Crossarms: Cables or messengers may be attached directly to the surface of poles and the clearance specified in Table 1, Cases 8 and 9 , shall not be held to apply provided all vertical clearances between conductors are maintained as specified throughout these rules.

 

(3)    Colinear Lines (See Rule 84.4–D3 )

 

(4)    Cables or Messengers Passing Supply Poles and Unattached Thereto (See Rule 84.4–D4 )

 

(5)    Cables or Messengers Passing and Unattached from Nonclimbable Street Lighting and Traffic Signal Poles or Standards (See Rule 84.4–D4a ).

 

Note:    Added January 8, 1980 by Decision No. 91186 and Revised March 9, 1988 by Resolution E–3076.

 

E.    Above or beside Buildings, Bridges and Other Structures (See Rule 84.4–E )

 

F.    Between Cables and Messengers

Cables supported by messengers are not required to be any specified distance from their supporting messengers.

 

G.    Between Messengers

No clearance between messengers is required where messengers of the same system branch or cross and the clearance specified in
Table 2, Case 1, Column A , does not apply in such instances.

 

H.    From Grounded Metal Boxes, Hardware and Equipment Associated with Supply Lines

Cables and messengers installed on non–metallic poles or non–metallic structures shall have a minimum clearance of 48 inches below or 72 inches above grounded metal boxes, hardware or metal cases for equipment associated with supply lines.

 

EXCEPTIONS:

 

(1)    The 72 inches above may be reduced to 48 inches where there is not a pole mounted communication drop distribution terminal 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 (see Figure 54–4 ).

 

(2)    The 72 inches above may 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.

 

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