This part of IEC 61466 is applicable to composite string insulator units with a specified mechanical load (SML) of 40 kN to 600 kN for AC overhead lines with a nominal voltage greater than 1 000 V and a frequency not greater than 100 Hz.

It also applies to insulators of similar design used in substations or for railway applications.

This standard applies to string insulator units of composite type with fittingsin accordance with IEC 61466‑1.

This standard specifies values for electrical and dimensional characteristics for composite insulators for overhead lines with a minimum lightning impulse withstand voltage (BIL) up to 3 100 kV and a specified mechanical load (SML) of 40 kN to 600 kN.