Jointing fittings are designed to connect insulators, to keep required distance, to joint the parts of multiple insulator string, to attach the insulator strings to the towers.
The fittings should be designed for mechanical loading caused by tensioning and weight of the conductors as well as other elements during normal working conditions, for additional loading caused by wind or frost. They should withstand the maximum strength guaranted by the manufacturer. The fitting must not be damaged. This is guaranted breaking strength, in catalogue refered as breaking strength.
The fittings should be designed for electrical loading. Nominal short-time current Ith per 1 second is based on the density of short-time current 70 A/mm², when starting temerature is 30 °C and max. temperature app. 400 °C, loading from 1 kN up to working loading.