adiabatic equation help!

assegayer · Mar 23, 2016

Hi guys,
really need help to solve this question i have on my assignment for my apprenticeship not asking for the answers but for guidance page numbers etc

Basically after cable cals i got 4mm2 for live conductors for one of the circuits they wanted me to work out and it is a 36m length run.

I know that i need to find the fault current and to do this i need r1 and r2 values i think? where do i get them from in OSG or regs?

also the the equation requires a disconnection time or something like that.

I would love some help, thanks guys

Simonslimline · Mar 23, 2016

assegayer said:
Hi guys,
really need help to solve this question i have on my assignment for my apprenticeship not asking for the answers but for guidance page numbers etc

Basically after cable cals i got 4mm2 for live conductors for one of the circuits they wanted me to work out and it is a 36m length run.

I know that i need to find the fault current and to do this i need r1 and r2 values i think? where do i get them from in OSG or regs?

also the the equation requires a disconnection time or something like that.

I would love some help, thanks guys

S=√I²t/K

AMD3 OSG Appendix I (page 189) for Resistance of conductors.

It will be (R1+R2) also mate. The smaller case refers to ring final circuit end to ends.

Once you have calculated the Ipf compare it to the graphs in BS7671 appendix 3 for the disconnection time.

Pete999 · Mar 23, 2016

assegayer said:
Hi guys,
really need help to solve this question i have on my assignment for my apprenticeship not asking for the answers but for guidance page numbers etc

Basically after cable cals i got 4mm2 for live conductors for one of the circuits they wanted me to work out and it is a 36m length run.

I know that i need to find the fault current and to do this i need r1 and r2 values i think? where do i get them from in OSG or regs?

also the the equation requires a disconnection time or something like that.

I would love some help, thanks guys

Appendix I Table 11

Leesparkykent · Mar 23, 2016

The adiabatic equation is given in reg 543.1.3. Values of K are given in tables 54.2 to 6. The time current characteristics of OCPD's are found in appendix 3. You need to know the fault current this can be derived from V/Zs. You can calculate Zs from the length of circuit and Ze.