under normal conditions. Number followed by
diagonal slash indicates quantity of insulators when
other than one. Environments with unusual
contaminant conditions would require special
treatment. Spool insulators for use with brackets,
or devices to support the neutral-messenger of
triplex or quadruplex, secondary or service cables
should conform to NEMA C29.3 Class 53-2. Use the
values in Table II for LANTNAVFACENGCOM projects.
TABLE I
NESC min.
ANSI
C29.7
NEMA
ANSI
Voltage
dry flashover
C29.5
Post
C29.2
C29.4
kV
kV
Pin
("L" or "S")
Suspension
Guy Strain
5. or less
20
55-1
57-1
52-1
54-1
7.2
39
55-3
57-1
2/52-1 or 2-52-9
54-1
13.2
55
55-3
57-1
2/52-1 or 2/52-9
54-2
23
75
55-6
57-2
2/52-4
54-3
C29.6
34.5
100
56-3
57-2
3/52-4
54-3
TABLE II
ANSI
ANSI
C29.7
NEMA
ANSI
Voltage
C29.3
C29.5
Post
C29.2
C29.4
kV
Spool
Pin
("L" or "S")
Suspension
Guy Strain
5. or less
53-2
55-3
57-1
52-1
54-4
15.
53-2
55-5
57-1
2/52-1
54-4
34.5
53-2
---
57-4
3/52-4
54-4
When specifying or indicating post insulators, add
the appropriate "L" or "S" designation indicating
"L" long studs or "S" short. Example: "57-1L"
would indicate an insulator for wood crossarms and
"57-1S" would indicate an insulator for use on steel
members. When the engineer determines that station
policy differs from these requirements, insulators
which match the policy in effect at the station
shall be specified by ANSI reference and class.
Insulator flashover values shall be determined from
Table 273-1, IEEE C2. In areas with severe
lightning problems, transmission line corners and
dead ends should be provided with special
pressure-treated wood-guy insulators having arcing
horns for lighting discharge. In addition to being
used with underground terminals, fiberglass guy
strain insulators shall be used where other
interference problems exist.
**************************************************************************
Provide wet-process porcelain insulators which are radio interference free.
[a. Line post type insulators:
NEMA C29.7, Class [_____].]
[b. Suspension insulators: NEMA C29.2 [4/52-4 for 34.5 kV on NAVSTA
NORVA], Quantity per Phase, [_____], Class [_____].]
SECTION 16301N
Page 17
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