General Order 64-A
Section V
Detailed Construction Requirements For Supply Lines
(Class H, L and T Circuits)
56.6 Insulation.
Where insulators are use in guys,
their values shall be calculated on the highest voltage carried at the level on
the pole, tower, structure or cross arm nearest which guy is attached and they
shall conform to the following specifications:
A. Material.
Insulators used on supply 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 supply lines
shall be so designed that their dry flash-over voltage is not more than 75% of
their puncture voltage at operating frequencies.
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 Engineers’ specifications as a minimum and
shall be capable of withstanding without flash-over at operating frequencies,
the voltages given in the following table:
|
Table 10 |
|
| Nominal voltage of circuits nearest point of attachments |
Minimum test dry flash-over voltage of insulator |
| 0-17,000 volts |
Double the circuit voltage |
| 17,000 volts and above |
35,000 volts |
D. Location.
(1)
Anchor: 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 on 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 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
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 the 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 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 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 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 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 )