The discs are to shed rain and to increase the surface tracking length, to ensure that if the voltage rises to breakdown, the bit that lets go first is the air gap between the metal horns, not the surface or the insulator core, The core up the middle, although the ends have metal hooks, is an insulator, these days usually an epoxy resin fibre composite.

The biggest problem now is that the field gradient along the insulator will be non-uniform and the flash-over voltage will be reduced.

However, 10/11 is not a big deal unless there are other stress factors like salt water spray or conductive dust.

Mike

The discs are to shed rain and to increase the surface tracking length, to ensure that if the voltage rises to breakdown, the bit that lets go first is the air gap between the metal horns, not the surface or the insulator core, The core up the middle, although the ends have metal hooks, is an insulator, these days usually an epoxy resin fibre composite.

The biggest problem now is that the field gradient along the insulator will be non-uniform and the flash-over voltage will be reduced.

However, 10/11 is not a big deal unless there are other stress factors like salt water spray or conductive dust.

Edit Google maps street view is marvellous.

Apologies, these are not solid cored insulators, but the disk and linked type- these look to be glass but the pin and shackle or ball and socket allows the disks to pivot relative to one another by a few degrees, in one or more dierections.

The path throuhg the insulation between the two bits of metal in each disk,  is only some 10s of mm, and although these are probably about 8 inches accross the surface track distance is going to be nearly 3 times that. The cap and pin and the mating surfaces on the glazed ceramic or glass are ribbed, so the cement has something to key into.

- here at both ends of what I think is the same line. At the power station end, there seems to be a longer strings , and corona disks (to shape the field a bit) while at the load end it is simple arc horns.

Mike

The discs are to shed rain and to increase the surface tracking length, to ensure that if the voltage rises to breakdown, the bit that lets go first is the air gap between the metal horns, not the surface or the insulator core, The core up the middle, although the ends have metal hooks, is an insulator, these days usually an epoxy resin fibre composite.

The biggest problem now is that the field gradient along the insulator will be non-uniform and the flash-over voltage will be reduced.

However, 10/11 is not a big deal unless there are other stress factors like salt water spray or conductive dust.

Edit Google maps street view is marvellous.

Apologies, these are not solid cored insulators, but the disk and linked type- these look to be glass but the pin and shackle or ball and socket allows the disks to pivot relative to one another by a few degrees, in one or more dierections.

The path throuhg the insulation between the two bits of metal in each disk,  is only some 10s of mm, and although these are probably about 8 inches accross the surface track distance is going to be nearly 3 times that. The cap and pin and the mating surfaces on the glazed ceramic or glass are ribbed, so the cement has something to key into.

- here at both ends of what I think is the same line. At the power station end, there seems to be a longer strings , and corona disks (to shape the field a bit) while at the load end it is simple arc horns.

Mike