General Order 64-A
Section VII
Detailed Construction Requirements For Trolley Lines
(Class T Circuits)
76.6 Insulation.
Where insulators are used in guys, their values shall be calculated on the highest voltage carried at the level on the pole, tower or structure or cross arm nearest which the guy is attached and shall conform to the following specifications:
A.
Material
Insulators used on trolley lines
shall be of porcelain, glass or other equally suitable material as regards
electrical and mechanical properties.
B. Strength. (See Rule 49.5-B.)
C. Voltage Requirements.
Insulators used on trolley lines
shall be so designed that their dry flash-over voltage is not more that 75 per
cent of their puncture voltage.
Insulators shall be capable of
withstanding the flash-over voltages given in the following table when under
mechanical loadings to which they are subjected.
Insulators shall be tested under
American Institute of Electrical Engineer’s specifications as a minimum and
shall be cable of withstanding without flash-over, the voltages given in the
following table:
Table 12 Insulator Minimum Flash-Over Voltages |
|
| Nominal voltage of circuit nearest point of attachment |
Minimum test dry flash-over voltage of insulators |
| 0-17,000 volts |
Double the circuit voltage |
| 17,0000 volts and above |
35,000 volts |
D. Location
(1) Anchors: Each anchor guy shall be equipped with an insulator so located that it shall at all times, be at least 8 feet vertically below the nearest supply or communication conductor and at least 8 feet vertically above the ground. Excepted from this rule are:
Guys attached to permanently grounded metal poles or structures or permanently grounded guys or poles or structures (not permanently grounded) from the conductor levels of 17,000 volts or more, provided, such guys are maintained a distance of at least 8 feet vertically from the nearest supply conductor of less than 17,000 volts on poles or structures not permanently grounded or 8 feet radially from the center line of any pole (other than those to which the guys are attached) carrying supply conductors of less than 17,000 volts on poles or structures not permanently grounded.
Guys from the level of conductors less than 16 feet above ground requiring insulators shall have same located at not less than 8 feet or more than 10 feet vertically above the ground. (See App. G, Figs. 18, 19, 20.)
(2) Overhead: Each overhead guy shall be equipped with two insulators so located that one shall be at a distance of 6 feet to 9 feet measured along the line of guy from each point of attachment to pole or structure and both shall be at least 8 feet vertically above the ground. Excepted from this rule are:
Guys between permanently grounded metal poles or structures or permanently grounded guys between poles or structures (not permanently grounded) from conductor levels of 17,000 volts or more, provided, such guys are maintained a distance of at least 8 feet vertically from the center line of any pole (other than those to which such guys are attached) carrying supply conductors of less than 17,000 volts on poles or structures not permanently grounded.
Guys from the level of conductors of any voltage between permanently grounded metal poles or structures and poles or structures not permanently grounded where said guys are in metallic contact with permanently grounded anchor guys, provided, such guys are maintained a distance of at least 8 feet vertically from the nearest supply conductor of less than 17,000 volts on poles or structures not permanently grounded or 8 feet radially from the center line of any pole (other than those to which such guys are attached) carrying supply conductors of less than 17,000 volts on poles or structures not permanently grounded.
Guys from the level of conductors of less than 17,000 volts between poles or structures not permanently grounded where said guys are in metallic contact with permanently grounded anchor guys. Said guys shall be equipped with one insulator located 6 feet to 9 feet measured along the line of the guy from the upper point of attachment, provided all permanently grounded sections of such guys are maintained a distance of at least 8 feet vertically from the nearest supply conductors of less than 17,000 volts on poles or structures not permanently grounded or 8 feet radially from the center line of any pole (other than those to which such guys are attached) carrying supply conductors of less than 17,000 volts on poles or structures not permanently grounded.
Guys less than 17 feet in length, requiring insulators between poles or structures not permanently grounded, in which case one insulator equidistant from each support will be sufficient. (See App. G, Figs. 22 to 25.)
(3) Truss: Each truss guy, the lower end of which is not grounded, shall be equipped with two insulators, one of which shall be located at least 8 feet below the lowest conductor and the other at least 8 feet vertically above the ground. Where the lower end is grounded the bottom insulator may be omitted. (See App. G, Fig 21.)