Decision Number 73813 GO 95 Section VI

The following rules cover certain special details for the construction of tower lines. These rules are supplemental to the rules given for supply lines in general and to the detailed construction requirements for supply lines, which rules must be observed in tower line construction, except as modified herein, or where clearly inapplicable.

Where steel supports or towers are used which are not capable of withstanding practically as great a stress longitudinally as transversely, longitudinal guying shall be used (see Rule 47.2) or anchor towers shall be placed at intervals not greater than 10 spans. Such anchor towers shall be capable of withstanding the combined longitudinal tension under the loadings of Section IV of all conductors up to 10,000 pounds plus one half the excess above 10,000 pounds.

All iron or steel of towers and all hardware subject to injurious corrosion under the prevailing conditions shall be protected by galvanizing, painting or other treatment which will effectively retard corrosion.

Overhead ground wires or lighting protection wires shall be galvanized steel cable not less than � inch in diameter, or other corrosion resistant material equal tensile strength. Where overhead ground wire are not used, effort shall be made to secure an effectively grounded structure.

Guys shall be galvanized steel strand not less than 5/16 inch in diameter, or other corrosion resistant material of equal tensile strength, or they shall be rolled rods of galvanized steel or other corrosion resistant material, with a tensile strength at least equivalent to 5/16-inch steel cable.

Anchor rods shall be galvanized steel not less than 5/8 inch in diameter or shall be of other material of equal strength and durability.

All metal towers shall be provided with steps or ladders, which shall start at not less than 7 feet 6 inches from the ground line and the spacings between steps on the same side of the tower legs shall not exceed 36 inches.

Where the members of the tower structure are so arranged that the tower may be climbed with safety or ladder need be provided.

All fabricated steel towers and similar structures which are of a design easily climbed and which are located in urban districts or in cultivated agricultural areas near roads or trails which are frequently traveled, shall be equipped with a sign so worded as to warn the public of the danger of climbing same. Such sign shall be placed and arranged so that it may be read from the four corners of the structure. Such signs shall be neither less than 8 feet nor more than 20 feet above ground except where the lowest horizontal member of the tower is more than 20 feet above the ground in which case the sign shall be not more than 30 feet above the ground.

Where lines supported by towers cross over major railroads (see Rules 22.3-B), or major communication lines (see Rule 20.5-A1), or other tower lines of voltage exceeding 30,000 volts, the towers supporting the crossing spans shall be designed to withstand, with safety factors as specified in Rule 44, the most severe conditions of temperature and loading specified in Rule 43 combined with the unbalanced pull which would be caused by any two conductors dead-ended or any two conductors broken in the span adjacent to the crossing.

~~The following rules cover certain special details for the construction of tower lines.~~ These rules are supplemental to the rules given for supply lines in general and to the detailed construction requirements for supply lines, which rules must be observed in tower line construction, except as modified herein, or where clearly inapplicable.

The following rules cover certain special details for the construction of tower lines and extra high voltage lines.

These rules are supplemented, in certain cases, by rules in other sections. See Section X for special rules applicable to line crossings or conflicts; see Section XI for special rules applicable to lines crossing railways.

61 ~~Maintenance and Inspection~~ ~~(See rules 31.1 and 31.2)~~ Towers and Structures

1) Tower Members: Tower members shall have a thickness of metal equivalent to the following:

Painted steel: Main corner members, 1/4 inch; other members, 3/16 inch. All iron or steel members of towers and all hardware subject to injurious corrosion under the prevailing conditions shall be protected by galvanizing, painting or other treatment which will effectively retard corrosion.

3) Overhead Ground Wires or Lightning Protection Wires: Overhead ground wires or lightning protection wires shall be galvanized steel cable not less than 1/4 inch in diameter, or other corrosion resistant material of equal tensile strength. Where overhead ground wires are not used, effort shall be made to secure an effectively grounded structure.

a) Guys: Guys shall be galvanized steel strand not less than 5/16 inch in diameter, or other corrosion resistant material of equal tensile strength, or they shall be rolled rods of galvanized steel or other corrosion resistant material with tensile strength not less than the tensile strength of 5/16 inch diameter galvanized steel strand.

b) Anchor Rods: Anchor rods shall be galvanized steel not less than 5/8 inch in diameter or shall be of equal strength and durability.

Where support structures are used which are not capable of withstanding substantially as great a stress longitudinally as transversely, longitudinal guying shall be used. The line as a whole shall be designed so that a failure of an individual support structure shall not cause successive failures of more than ten additional support structures.

All towers or structures which are of a design easily climbed and which are located in urban districts or in cultivated agricultural areas or near roads or trails which are frequently traveled shall be equipped with signs so worded as to warn the public of the danger of climbing same. Such signs shall be placed and arranged so that they may be read from the four corners of the structure. Such signs shall be neither less than 8 feet nor more than 20 feet above the ground except where the lowest horizontal member of the tower or structure is more than 20 feet above the ground in which case the sign shall be not more than 30 feet above the ground.

Where a tower or a design which can be easily climbed supports supply conductors and is located in urban districts, or in rural areas adjacent to schools, dwellings, permanent or seasonal camps, or in orchards, or near roads or trails which are frequently traveled, a barrier or other provisions shall be made to prevent easy climbing.

The provisions of this rule shall not apply to towers or structures on which all conductors have a 5 feet or more horizontal clearance from the supporting structure, nor to towers or structures within fenced substation yards.

Note: It is the intent of Rule 61.6-B to require such guarding as will prevent easy climbing of these towers by young persons who do not realize the danger of contact with live conductors supported thereon. It is not intended that such guarding will be required in sparsely settled districts, mountainous and desert areas, and similar locations.

All towers upon which it may be necessary for workmen to climb shall be provided with steps or ladders, which shall start at not less than 7 feet 6 inches from the ground line. The spacing between steps on the same side of the tower legs shall not exceed 36 inches.

Where the members of the tower are so arranged that the tower may be climbed with safety, no steps or ladders need be provided.

63.1 ~~Tower Members~~ Maintenance and Inspection (See Rules 31.1 and 31.2)

63.2 ~~Overhead Ground Wires~~ Material and Strength (See Rule 49.5)

~~Overhead ground wires or lighting protection wires shall be galvanized steel cable not less than � inch in diameter, or other corrosion resistant material equal tensile strength.~~ ~~Where overhead ground wire are not used, effort shall be made to secure an effectively grounded structure.~~

63.3 ~~Guys and Anchors~~ Deadend and Suspension Spacing (See Table 1 and Table 2)

~~Anchor rods shall be galvanized steel not less than 5/8 inch in diameter or shall be of other material of equal strength and durability.~~

Bonding is not required by these rules. It is recognized that under certain conditions it may be deemed necessary. Where phase-to-phase bonding is used, the bond wire or strap shall have a conductivity of not less than No. 10 AWG copper wire.

~~Where the members of the tower structure are so arranged that the tower may be climbed with safety or ladder need be provided.~~

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

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 Structure, 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.

2) On the Same Crossarms, Same Phase or Polarity: The clearance specified in Table 2, Cases 15 and 17, are not required between conductors of both the same potential and the same phase or polarity, such as bundle conductors.

All fabricated steel towers and similar structures which are of a design easily climbed and which are located in urban districts or in cultivated agricultural areas near roads or trails which are frequently traveled, shall be equipped with a sign so worded as to warn the public of the danger of climbing same. ~~Such sign shall be placed and arranged so that it may be read from the four corners of the structure.~~ Such signs shall be neither less than 8 feet nor more than 20 feet above ground except where the lowest horizontal member of the tower is more than 20 feet above the ground in which case the sign shall be not more than 30 feet above the ground.

Insulators used on high voltage supply lines shall be porcelain or other equally suitable material to withstand the applied voltage.

Where mechanical loads imposed on towers or structures are greater than can be supported with safety factors as specified in rule 44 or the design of such towers and structures requires it, additional strength shall be provided by the use of guys or other suitable construction.

Where guys are used with structures capable of considerable deflection before failure, the guys shall be able to support the entire load, the structure below the point of guy attachment acting merely as a strut.

Guys shall be attached to structures, as nearly as practicable, at the center of load. They shall be maintained taut and of such strength as to meet safety factors of rule 44.

The basic minimum clearances of overhead guys above the ground and from other wires or cables are specified in tables 1 and 2. Modifications of these basic clearances are specified in rules 37 and 38. the minimum clearance of 18 feet for overhead guys of high voltage supply lines shall not be decreased along public thoroughfares or railways.

For clearances of anchor guys from overhead guys, span wires and conductors supported on other poles or structures, see Rule 56.4.

Anchor guys shall be protected by the use of guy thimbles or their equivalent where attached to anchor rods or through bolts.

Anchor guys exposed to high voltage supply lines shall be securely grounded but may be sectionalized. Anchor guys which are attached to grounded towers or structures need not be provided with a separate ground.

The following rules cover certain special details for the construction of tower lines and extra high voltage lines.

1) Tower Members: Tower members shall have a thickness of metal equivalent to the following:

2) Overhead Ground Wires or Lightning Protection Wires: Overhead ground wires or lightning protection wires shall be galvanized steel cable not less than 1/4 inch in diameter, or other corrosion resistant material of equal tensile strength. Where overhead ground wires are not used, effort shall be made to secure an effectively grounded structure.

b) Anchor Rods: Anchor rods shall be galvanized steel not less than 5/8 inch in diameter or shall be of equal strength and durability.

Where support structures are used which are not capable of withstanding substantially as great a stress lon3gitudinally as transversely, longitudinal guying shall be used. The line as a whole shall be designed so that a failure of an individual support structure shall not cause successive failures of more than ten additional support structures.

Where a tower of a design which can be easily climbed supports supply conductors and is located in urban districts, or in rural areas adjacent to schools, dwellings, permanent or seasonal camps, or in orchards, or near roads or trails which are frequently traveled, a barrier or other provisions shall be made to prevent easy climbing.