Calculating Zs for known and unknown cable length.

[ulfr]

Hi guys,

Am I doing Continuity test calculations in a right way?

For unknown length of a cable:
Circuit breaker B16A, let Ze be 0.26 ohms. Zs from Table B6 (OSG, p125).
MAX Zs-Ze = Max expected (R1 + R2) = 2.2 - 0.26 = 1.94 ohms

For known length:
Let's assume the cable is twin with 1.5x1.5mm2 line and cpc, and Ze=0.26ohms, and length is 2m.
R1+R2 from OSG p.189 Table I1 but in mili ohms! So we would have to convert to ohms *10(-3)

Zs=Ze+(R1+R2)=0.26+(2m * 24.20 * 10(-3) ) = 0.26 + 0.0484 = 0.3084 ohms which gives 308.4 mOhms.

Is that correct? And which numbers do I need to write as a test result? Ohms or mili Ohms?

Thanks.

 

[telectrix]

on test sheets, you enter resistances in ohms, usually to 2 dec. places.