The present International Standard pertains to long rod string insulator units featuring ceramic insulating components, designed for installation in a.c. overhead transmission lines with nominal voltages exceeding 1,000 V and frequencies not exceeding 100 Hz. It also applies to comparable insulators utilized within substations.
This standard encompasses ceramic long rod string insulator units, which may either be equipped with a clevis end fitting at both ends for connection with a tongue, or a socket end fitting at both ends for engagement with a pin ball.
The purpose of this standard is to establish specific values for the electrical and mechanical properties, as well as the primary dimensions of the long rod ceramic string insulator units.
The standard is applicable to string insulator units intended for use on overhead lines in areas with low levels of pollution, and the creepage distances specified in Table 1 are based on the IEC 60815 recommendation of 1.6 mm/kV for Pollution Level I. Nevertheless, shorter creepage distances can be employed in certain unpolluted regions. Should non-standard (either longer or shorter) creepage distances be necessitated by particular operating conditions, the mechanical properties and lengths L (refer to Clause 4) as outlined in this standard should be utilized, unless exceptional circumstances demand lengths exceeding those listed in Table 1. In instances of specialized requirements, such as highly polluted areas or other unique or extreme environmental conditions, alterations to certain dimensions might be required.
NOTES:
- To the extent feasible, this International Standard can also be applied to similar insulator units that fall outside the scope of this standard, such as insulators for electric traction systems.
- This International Standard does not encompass testing procedures for insulators or the dimensions of end fittings.
- Ball and socket couplings are governed by IEC 60120, while clevis and tongue couplings are covered by IEC 60471.
- For the definition of pollution levels, refer to IEC 60815.
- The term “ceramic” in this International Standard denotes porcelain materials, and it does not include glasses as is common in North American practices.
