This International Standard is applicable to string insulator units of the long rod type with insulating parts of ceramic material intended for use in AC overhead power lines with a nominal voltage greater than 1 000 V and a frequency not greater than 100 Hz. It is also applicable to insulators of similar design, used in substations.

This document is applicable to ceramic string insulator units of the long rod type, either with a clevis end fitting at both ends for coupling with a tongue, or with a socket end fitting at both ends for coupling with a pin ball.

The object of this document is to prescribe specified values for electrical and mechanical characteristics, and for the principal dimensions of ceramic string insulator units of the long rod type.

This document is applicable to string insulator units for use on overhead lines situated in lightly polluted areas, and the creepage distances given in Table 1 have been established accordingly, using the IEC TS 60815-2 recommendation of 27,8 mm/kV for SPS class. However, shorter creepage distances are applicable for use in some non-polluted areas. If specific operating conditions require or allow non-standard (longer or shorter) creepage distances, the mechanical characteristics as well as the lengths L (see Clause 4) of this document are intended to be used unless the need for exceptionally long creepage distances requires values of L greater than those given in Table 1. In the case of special requirements, e.g. very heavy polluted areas and for other particular or extreme environmental conditions, it may be necessary for certain dimensions to be changed.

As far as reasonably applicable, this document is also applicable to be applied to similar insulator units outside the scope of this standard, such as insulators for electric traction lines. This document does not include tests on insulators and dimensions of end fittings.

Ball and socket couplings are covered by IEC 60120, clevis and tongue couplings by IEC 60471.

NOTE 1 For the definition of site pollution severity, see applicable part of IEC TS 60815.

NOTE 2 The term "ceramic" is used in this document to refer to porcelain materials and, contrary to North American practice, does not include glass.