My flat is 50m to the nearest car parking spot and I want a portable Extension lead to run a 2kw vacuum with trailing socket but wish to make my own up. The length would need to be 60m. What size cable do I need please? Cheers
To keep within the 6% volt drop then the cable needs Voltage Drop (per ampere per meter) better than 0.026 so 2.5 mm sq is the smallest cable you could use which is also about the maximum size one can get into a 13A plug. At that distance to comply it would need RCD protection as the earth loop impedance would be too high for any fuse to protect. You should of course have RCD protection to all sockets now but there are still some old installations.
That's the answer I should give but I know with 110 volt supplies at building sites I have seen that much cable feed a vacuum cleaner at 80 meters which due to reduced voltage is more of a problem then with 230v and it worked with 2.5 mm sq cable so at 230 volt very likely 1.5 mm sq cable would work however the vacuum would run slow and again must say how important the RCD is at that distance.