help with my 2391- equations?

[vbyrne]

I am looking help with some equations that could come up in my 2391 exam ,is there any body out there that could explain to me from start to finish how I calculate voltage drop.

 

[IQ Electrical]

Voltage drop = (mV/A/mtr) x Ib x L /1000

(mV/A/mtr) – mV drop per amp per mtr Found in BS7671/OSG

Ib – Design Current

L – Length of cable run in meters

 

[topquark]

.... as above and if it's a three phase circuit (distribution etc). Then adjust the table values by dividing by square root of 3 and include adjusted reactance figure as well (add the two together). Finally you may need to adjust the resistance (but not reactance) for temperature (depending on what table you are using).