IEC 60433-2021 pdf Insulators for overhead lines with a nominal voltage above 1 000 V – Ceramic insulators for AC systems – Characteristics of insulator units of the long rod type

3 Terms and definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: • • IEC Electropedia: available at http://www.electropedia.org/ ISO Online browsing platform: available at http://www.iso.org/obp 3.1 long rod insulator suspension or tension insulator consisting of an approximately cylindrical insulating part provided with sheds and equipped at the ends with external metal fittings Note 1 to entry: The insulator is designed in such a manner that the shortest puncture path through solid insulating material is at least equal to half the arcing distance. Therefore it is a class A insulator according to IEC 60383-1. 4 Characteristics, dimensions and type of long rod insulators String insulator units of the long rod type are characterised by the following specified characteristics: – the standard lightning impulse withstand voltage (see IEC 60071 -1); – the wet power frequency withstand voltage (see IEC 60071 -1); – the tensile mechanical failing load; – the maximum nominal length L of the insulator; – the maximum nominal diameter D of the insulating part; – the minimum nominal creepage distance; – the standard coupling. The corresponding values are specified in Table 1. The minimum nominal creepage distances are based on a unified specific creepage distance of 27,8 mm/kV for the lowest value of the highest voltage for equipment corresponding to the specified value of the standard lightning impulse withstand (in accordance with IEC 60071 -1). NOTE 1 The tolerances given in IEC 60383-1 are applicable to all the dimensions in Table 1, even if the adjectives “minimum” or “maximum” are used before the term “nominal”. NOTE 2 Dry lightning impulse withstand voltage and wet power frequency withstand voltage are specified in Table 1 for single unit string insulators.
The insulators shall be marked either on the upper shed or on the metal parts with the name or trade mark of the manufacturer and the year of manufacture. In addition, each unit shall be marked with the specified mechanical failing load, by using the first part of the designation; for instance, the insulator shall be marked L 160 for the units with 160 kN specified mechanical failing load. These markings shall be legible and indelible. Figure 1 shows a long rod insulator with clevis couplings. Figure 2 shows a long rod insulator with socket couplings.