Adiabatics

[sparks1234]

I understand using the equation and how to work them out, but can someone explain the point of usage of them and why you use them

 

[ezzzekiel]

to calculate that under fault condition the cpc can carry the ammount of fault current created till disconnection occurs

 

[sparks1234]

And would this be a calc to do once the install is in or before or maybe either

 

[ezzzekiel]

usually done before during design process bit late after
nominal cpc sizes are usually a lot bigger any way

 

[sparks1234]

usually done before during design process bit late after
nominal cpc sizes are usually a lot bigger any way

Sorry, when I said that I was thinking of using it to check during a PIR.

 

[skatingsparks]

I think the adiabatic equation is used to ensure that the size of the CPC is large enough that when the circuit is under fault earth conditions it allows sufficient current to flow to cause the protective device to operate fast enough before the fault current flowing damages the cable and that why there are different k factors. Some cables are more resilient that others. Does that make sense? If the CPC is to small the fault current flowing will not cause disconnection before the fault current damages the cable.