Original General Order
95
Section
V
Detailed Construction Requirements for Supply Lines
(Class H, L
and T Circuits)
55.3 Voltage Requirements
Insulators used on Supply lines shall be so designed that their dry flashover voltage is not more than 75% of their puncture voltage at operating frequencies.
A. Pin Type
All pin type insulators used on supply lines shall have a dry flashover voltage as specified in Rule 55.3-C for the nominal line voltage at which they are used.
B. Suspension and Strain Types
Suspension and strain type insulators used on supply lines shall have a dry flashover voltage as specified in Rule 55.3-C for the nominal line voltage at which they are used when tested with their attaching fittings or harness and under the mechanical loading to which they are to be subjected.
C. Flashover Voltage
The insulator flashover voltages required by Rules 55.3-A and 55.3-B shall be not less than as shown in Table 12 and shall be determined in accordance with Standards of the American Institute of Electrical Engineers for Insulator Tests, Standard Number 41 dated March 1930.
Table 12 Insulator Flashover Voltages |
|
| Nominal Line Voltage |
Dry flashover voltage |
|
750 |
5,000 |
|
2,300 |
20,000 |
|
4,000 |
30,000 |
|
6,600 |
40,000 |
|
11,000 |
50,000 |
|
22,000 |
75,000 |
|
33,000 |
100,000 |
|
44,000 |
125,000 |
|
55,000 |
140,000 |
|
66,000 |
170,000 |
|
88,000 |
220,000 |
|
110,000 |
315,000 |
|
132,000 |
390,000 |
|
150,000 |
420,000 |
|
200,000 |
560,000 |
For intermediate voltages above 750 volts the value for flashover may be obtained by interpolation.
D. Additional Insulation
Insulators used in territories where fog or lighting conditions prevail should be given more liberal factors of safety than those indicated in Table 12.
Insulators used at crossings or conflicts shall conform to Rules 104 and 114.