UK 18th edition help

[Daniel Smith]

What is the calculation required For the image attatched? Any help would be appreciate, thanks.

 

[SparkyChick]

It's not a calculation as such. I presume it's an open book exam?

There are tables (the one for this is the one on page 368 I believe) that show the tripping characteristics of various devices. You lookup the table for the device and then look at the line for the device rating and read of the time.

 

[Vortigern]

Look up the time curves in the BBB.