Adiabatic Equation question

[lilman]

Afternoon all - I should probably know this but I thought I'd check with others:

I would like to know the suitability of the 6mm cpc in a 16mm T&E as a submain. Voltage 230V, Zs 0.15ohm, 80A BS1361 in switchfuse. So I = 230V/0.15ohm = 1533.33A. This value is beyond the curve on the time/current characteristics of the 80A fuse. So my question is - do I use the lowest time value of 0.1 seconds in the adiabatic equation? I hope this makes sense.

Cheers

 

[Evans Electric]

It used to be OK for the 16th , has it altered with the 17th then ? You will have full RCD protection with the 17th so why is there a problem ?

The adriatic quotation is a bit frightening methinks.

Deke

 

[Robojin]

Afternoon all - I should probably know this but I thought I'd check with others:I would like to know the suitability of the 6mm cpc in a 16mm T&E as a submain. Voltage 230V, Zs 0.15ohm, 80A BS1361 in switchfuse. So I = 230V/0.15ohm = 1533.33A. This value is beyond the curve on the time/current characteristics of the 80A fuse. So my question is - do I use the lowest time value of 0.1 seconds in the adiabatic equation? I hope this makes sense.

Cheers

If my maths is correct 80A = DT of 5s, your cpc would need to be 8.94mm2 so 16/10 for cable selection based on your numbers and fuse type

 

[Jono Pashley]

wouldnt 5 seconds be the max allowable disconnection time, not the operation time.

 

[Robojin]

wouldnt 5 seconds be the max allowable disconnection time, not the operation time.

The OP was referencing the BRB hence my reply regarding 10mm cpc, so yes to your first comment, and operational time would down to the design characteristics of the protective device