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VD Topic Question one

VD Topic Question one

by jye leckner -
Number of replies: 5

Determine the minimum conductor size for a final sub-circuit supplying a single-phase 230V power circuit protected by a 20A Circuit breaker. The circuit consists of TPS cable with copper conductors in a roof space. The route length of the circuit is 38m, and the voltage drop in the existing consumer's mains is 3V. 

Voltage drop permissible in the final subcircuit. Answer

Find the maximum Vc Value for the cable Answer

Minimum size cable as per table Answer mm2


In reply to jye leckner

Re: VD Topic Question one

by Brandon Pretorius -

After working it out, I found:

The Voltage drop in final subcircuit = 8,13 V = 3.5%

Vc value = 3.86 mV/A.m

Cable size = 10mm2  

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In reply to Brandon Pretorius

Re: VD Topic Question one

by Zhaobing Ma -
Vd<=230*5%-3=8.5V
Vc=1000*Vd/(L*I)<=11.18mV/A.m
Convert to three phase Vc=11.18*0.866=9.69
AS3008 Tab 42 Col 6
Vc=6.49
Minimum conductor size 6mm2.