This part of IEC 61466 is applicable to composite string insulators with a specified mechanical load (SML) of 40 kN and 70 kN for a.c. overhead distribution 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 on electric traction lines.
This standard applies to string insulator units of composite type with couplings in accordance with IEC 61466-1.
This standard prescribes specified values for electrical and dimensional characteristics of composite string insulator units for overhead distribution lines with a highest lightning impulse level of 325 kV and a specified mechanical load (SML) of 40 kN and 70 kN.
NOTE - General definitions and methods of testing are given in IEC 61109.