Overhead line porcelain insulators can be divided into ball and socket disc insulators, line post insulators, clamp top insulators and other type insulators.

Ball and socket disc insulators

Ball and socket disc insulators shall comply with designation U 70 BL (for Items 19 & 21) and U 70BLP (for Item 20) as defined in AS 60305 and shall have standard couplings complying with AS 60372. The locking devices shall be “W” clips type 16B in accordance with AS 60372. Similarly for 125kN type insulators (items 22 and 23) the locking devices shall be “R” clips type 16 – in accordance with AS60372. Ferrous metal fittings shall be hot dip galvanized to AS 4680. The thickness of the zinc coating for item 19 shall comply with the acceptance criteria set out in clause 26 of AS 2947.1. Preference will be given to the insulators that exceed these criteria.
For items 20 and 21, the minimum and the average thickness of the galvanizing on the insulator pin shall be 130 and 140 microns respectively. The galvanizing on the cap shall comply with AS2947.1. Preference will be given to the insulators that exceed these criteria.
Further, all insulators shall be supplied with zinc sleeves.

Line post insulators
Line post insulators are to be supplied complete with a M20/24 galvanized steel stud complete with spring lock washer, round washer and nut as specified in Attachment 1. The base of the insulators shall be in accordance with Table ii and Figure 8 of AS IEC60720 as applicable. The size of the threaded hole for the stud shall be in accordance with the requirement.

Clamp top Line post insulators

The clamp top fitting of line post insulators shall be in accordance with Figure 6 and Figure 4 or 5 of AS IEC60720 as applicable. Conductor clamps suitable to accommodate aluminum based conductor with/without armor rods with overall diameter between 5.3 to 18.8mm shall be supplied with the insulators. Conductor clamps are not required for the 66kV insulators.

Ferrous material other than stainless steel shall be galvanized in accordance with AS 4680.