sizing meter tails and switch fuse discrimination

[jase31]

DNO has upgraded service fuse from 30a to 60a, they do not want to go any higher due to the main feed cable.

CU is 4-5m away, connected via switchfuse. Should 16mm or 2mm tails be used, OSG recommend 25mm but seems to assume a 100a supply.

With a 60a head, what size switchfuse should be used for discrimination?

 

[Deleted member 26818]

The DNO fuse is protecting their equipment.
Don't worry about discrimination with their fuse.

 

[i=p/u]

hi spin london, when sizing cables 25mm and above what do you use as Mv/A/m there is 3 options, isit normal too use z option????

 

[jase31]

The DNO fuse is protecting their equipment.
Don't worry about discrimination with their fuse.

With a 60a head, I cant really see the need for a customer switch fuse for 25mm tails that are 4-5m long, but I understand that DNO insist on a switchfuse over 3m. What fuse should be used? 60A

 

[telectrix]

16mm tails and a 60A fuse. keep it simple.

 

[Guest123]

hi spin london, when sizing cables 25mm and above what do you use as Mv/A/m there is 3 options, isit normal too use z option????

Upto 35mm, I continue to use the resistive (r) component for calculating the VD. By moving to the impedance (z) component you will end up with a pessimistically large conductor size.

Going above 35mm and bringing reactance & impedance in to play makes it all a bit more complicated as power factors (if known) and temperature corrections come into play.

Have a read from page 312 (new green book) onwards (appendix 4).