If you have a 3 phase main cable protected by 400 amp fuses what size is the cross section area of each core? Also what would be the size of a single phase take off from this if its protected by a 100 amp fuse at the load end? As you mite of guessed I'm talking DNO cables
new 100 A services are likely to present in 35mm from the street to the house, the street main is fatter. This is not so much a cable current rating thing , but to ensure the substation fuse pops before the house supply cable, at least for a dead short.
Older stuff, who knows. not always the DNOs even. But the older lead clad oily paper sort of cable was better cooled and could take excursions to well over 100C without failure, so do not compare just core area with a modern PVC or XPLE insulation.
Even so 4mm2 is probably a bit mean, but something between 6 and 10 is credible, and probably OK on a 60A service fuse as often in a 100A holder.
DNOs vary a bit but not much, this is UKPNs for new connections from EDS 08-2100
available here UKPN library You do have to create an account to access this, but it is only an Email and there is a lot of other useful stuff. . You can always put IET forum user in the 'job description' if you wish to be coy.
Mike.
new 100 A services are likely to present in 35mm from the street to the house, the street main is fatter. This is not so much a cable current rating thing , but to ensure the substation fuse pops before the house supply cable, at least for a dead short.
Older stuff, who knows. not always the DNOs even. But the older lead clad oily paper sort of cable was better cooled and could take excursions to well over 100C without failure, so do not compare just core area with a modern PVC or XPLE insulation.
Even so 4mm2 is probably a bit mean, but something between 6 and 10 is credible, and probably OK on a 60A service fuse as often in a 100A holder.
DNOs vary a bit but not much, this is UKPNs for new connections from EDS 08-2100
available here UKPN library You do have to create an account to access this, but it is only an Email and there is a lot of other useful stuff. . You can always put IET forum user in the 'job description' if you wish to be coy.
Mike.
