Voltage Drop Calculation

by Steve on December 7, 2009

To Calculate Voltage Drop

Reference to:Regs  App 4.6OSG Appendix 6   

This is the formula for volt drop calculations.

Voltage drop = (mV/A/mtr) x Ib x L


(mV/A/mtr) – mV drop per amp per mtr   Found in Regs App 4 & OSG App 6 Tables.

Ib – Design Current

L – Length of cable rum in meters

The resulting volt drop must then be multiplied by a factor of 1.20.  This is the factor from table 9C in the on site guide to correct for the rise in temperature when the circuit is under load.

Maximum Voltage Drop allowed.


{ 1 comment… read it below or add one }

bas September 14, 2011 at 14:05

The mV/A/m values in Appendix 4 of the regs and Appendix 6 of the OSG already assume a conductor temperature of 70°C.

Why do you want to multiply your calculated voltage drop figure by 1.2 to allow for a temperature rise from 20°C to 70°C?

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