Calculating Zs!

[Nic Norwood]

Just a quick check to see if my math's are right for NVQ3 assessment.

Ze - 0.01 Ohms
Circuit length - 28m
CSA of line and cpc - 2.5mm2
Conductor material - Copper

[FONT=Calibri, sans-serif]R1=pL/A[/FONT]
[FONT=Calibri, serif][FONT=Calibri, sans-serif] R1=((1.78x10-8)x 28) / (2.5 x10-6)[/FONT][/FONT]
[FONT=Calibri, serif][FONT=Calibri, sans-serif] R1=0.19Ohms[/FONT][/FONT]


[FONT=Calibri, serif][FONT=Calibri, sans-serif] R2=pL/A[/FONT][/FONT]
[FONT=Calibri, serif][FONT=Calibri, sans-serif] R2=((1.78x10-8)x 28) / (2.5 x10-6)[/FONT][/FONT]
[FONT=Calibri, serif][FONT=Calibri, sans-serif] R2=0.19Ohms[/FONT][/FONT]


[FONT=Calibri, serif][FONT=Calibri, sans-serif] Zs= Ze + (R1+R2)[/FONT][/FONT]
[FONT=Calibri, serif][FONT=Calibri, sans-serif] Zs= 0.01 + (R1+R2)[/FONT][/FONT]
[FONT=Calibri, serif][FONT=Calibri, sans-serif] Zs= 0.38 Ohms[/FONT][/FONT]

 

[KAS1]

What are you using to work out R1 and R2 ?

 

[Nic Norwood]

What are you using to work out R1 and R2 ?

Forgive me if I've missed something, but I am using the formula to calculate the resistance of a conductor using the information given regarding the materials specific resistivity, length and area.

 

[KAS1]

I think the resistance of copper 2.5mm is 7.41mOhms /M

 

[martinh287]

Sounds about right I worked out 0.20 ohms using a slightly different method

18.10 ÷ 2.5 * 28 = ___ ÷ 1000 = 0.20 ohms

Your result is more accurate however

 

[KAS1]

Zs= 0.01 + (R1+R2) Zs= 0.01 + ( 7.41 X 28 X R2 )/1000

 

[Guest55]

Zs for 28mtrs of 2.5 / 2.5

(7.41 + 7.41 ) x 28 / 1000 = 0.41

( 0.41 x 1.2* ) + Ze

0.5 + 0.01 = 0.51 ohms

* max operating cable temp adjustment factor for 70 deg. pvc.

 

[Nic Norwood]

Zs for 28mtrs of 2.5 / 2.5

(7.41 + 7.41 ) x 28 / 1000 = 0.41

( 0.41 x 1.2* ) + Ze

0.5 + 0.01 = 0.51 ohms

* max operating cable temp adjustment factor for 70 deg. pvc.

Thanks for the advice, though they may be wrong, I think that I'm best off sticking with the values of resistivity that the college have given me to work out my resistance. However would you be able to point me to information regarding the correction factor of 1.2 for the temp adjustment.

 

[Guest55]

page 184 of on-site guide.