Failures occurring in practice are usually due to lightning or to deposits of soot or sea salt on the insulator surface. Lightning affects the design of the transmission line rather than that of ...

For overhead lines up to 33 kV and for outdoor substation equipment, the insulator is typically of the post insulator type ... used on low voltage distribution lines and long rods at transmission ...

Above this voltage and up to about 132 kV system voltage 'line post' insulators may be used or, more usually, from 40 kV to the highest transmission system voltages the 'cap and pin' insulator is used ...