EN IEC 60305-2021 Insulators for overhead lines with a nominal voltage above 1 000 V – Ceramic or glass insulator units for AC systems – Characteristics of insulator units of the cap and pin type (IEC 60305:2021).
3 Terms and definitions
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4 Mechanical characteristics, dimensions and types
String insulator units of the cap and pin type are standardized by the following specified characteristics:
– Specified electromechanical or mechanical failing load (SFL) according to IEC 60383-1 ;
– maximum nominal diameter of the insulating part;
– nominal spacing;
– minimum nominal creepage distance;
– standard coupling.
The corresponding values are indicated in Table 1 , Table 2, Table 3, Table 4 and Table 5.
NOTE 1 The following points merit attention for insulators for use in polluted areas:
a) even if the creepage distance is the same, the withstand voltage characteristics may change with shed shape of the insulators;
b) even if the string length is the same, the withstand voltage characteristics may decrease with increasing insulator strength due to the lower efficiency of creepage distance for a larger average diameter.
NOTE 2 IEC 6081 5 gives details on the important parameters of shed profiles for antipollution insulators.
5 Designation and marking with respect to shed profile
Insulators are designated in Table 1 , Table 2, Table 3, Table 4 and Table 5 by the letter U followed by a number indicating the specified electromechanical or mechanical failing load in kilonewtons.
The letter B or C which follows specifies a ball and socket or clevis and tongue, respectively.
The following letter S or L, if present, specifies a short or long spacing.
The letter P, D, V, or T present for “anti-fog” profile, “aerodynamic” profile, “two-alternating” profile, or “three-alternating” profile, as shown in Figure 1 , Figure 2, Figure 3,Figure 4 andFigure 5, respectively.
IEC 60383-1 specifies that insulators shall be marked with the specified electromechanical or mechanical failing load. This load may be indicated by using the first part of the designation given in the first column of Table 1 , Table 2, Table 3, Table 4 and Table 5: For instance, the insulator may be marked U 1 60 for the units U 1 60 BS, U 1 60 BL and U 1 60 BLP.
Except for nominal spacing, tolerances for dimensions indicated in IEC 60383-1 are applicable to all nominal values including maximum nominal diameter and minimum nominal creepage distance values given in Table 1 , Table 2, Table 3, Table 4 and Table 5.
Diagram of Table 1 , Table 2, Table 3, Table 4 and Table 5 is shown in Figure 6, Figure 7,
Figure 8, Figure 9 and Figure 1 0, respectively.
Nominal spacing tolerance shall be:
± (0,03 P + 0,3) mm
P being spacing expressed in millimetres.EN IEC 60305 pdf download.