Disconnection under ADS

[Readytorum]

Hi. I'm currently doing my design project and have submitted the first draught I've managed to correct most of my feedback but am struggling with question 5, Determine, for one of the fridges the minimum possible CSA area of CPC which will satisfy the requirements disconnection as ads under earth fault conditions and the adiabatic equation as reg 543.1.3. The feedback I received for my first attempt was suggestive of thermal constraints and that it talks about ADS remember it's 16A *5 80A. How do I go about this as I always seem to go back to my original answer? Thanks

 

[Lister1987]

Hi. I'm currently doing my design project and have submitted the first draught I've managed to correct most of my feedback but am struggling with question 5, Determine, for one of the fridges the minimum possible CSA area of CPC which will satisfy the requirements disconnection as ads under earth fault conditions and the adiabatic equation as reg 543.1.3. The feedback I received for my first attempt was suggestive of thermal constraints and that it talks about ADS remember it's 16A *5 80A. How do I go about this as I always seem to go back to my original answer? Thanks

This is telling you to run the adiabatic equation in Part 5 (Selecting conductor CSA - S = √(I2t)/ k) and not the one from Part 4 (Thermal Withstand - t = k2s2 / I2). You can run thr part 4 equation but you'll already know what disconnection times you'll need to hit.

If your sizes work out then the last check is I2t < K2S2 - Is thr energy let through WITHIN (or less than) the total energy that thr conductor will take before degrading.

Don't forget to add statements to the fact at each part of the equation;

"I believe % under reg # is met because" (or the inverse; is NOT met because)

For % substitute the part of the process; coordination, volt drop, thermal withstand, conductor sizing etc)

For # substitute the regulation number that applies.

Where you're saying the design is not compliant then you need to offer resolutions (bigger cable/OCPD), bonus points for mentioning consideration for Appendix 17 and consideration of potential saving in energy efficiency vs outlay