Conductor Resistances and Reactances Dilemna
Conductor Resistances and Reactances Dilemna
(OP)
Hi to all. I am looking into NEC table 9.1.1.9 and gives me the value of insulated conductor or cable resistances, reactances and impedances in terms of "Line-To-Neutral". Does line-to-neutral impedance synonimous to "Impedance per Phase" or Single Phase Impedance?
It is confusing that the Table is entitled"Alternating Current Resistance and Reactance for 600volts Cables, 3phase, 60Hz, 75 deg C-Three Single Conductor in Conduit" while the values are in Ohms to neutral.
It is confusing that the Table is entitled"Alternating Current Resistance and Reactance for 600volts Cables, 3phase, 60Hz, 75 deg C-Three Single Conductor in Conduit" while the values are in Ohms to neutral.






RE: Conductor Resistances and Reactances Dilemna
RE: Conductor Resistances and Reactances Dilemna
Vdrop line-to-line = 1.732 * highest current on phase *
Z(line-to-neutral).
the 1.732 multiplier, although the line current is single phase will account on the assumption of a balanced three phase to simplify the calculation. Is my understanding correct.
If I do have my 3phase load current, single phase line-to-line load current and single phase line-to-neutral load current, using a Ohms to neutral impedances from Table 9.1.1.9, are these correct for me to calculate the watts losses on these cables?
1. Cond. Watts loss 1phase, L-L = 2*[I(line-line)]^2 * R
2. Cond. Watts loss 1phase, L-N = [I(line-line)]^2 * R
3. Cond. Watts loss 3phase, = 3*[I(line-line)]^2 * R
RE: Conductor Resistances and Reactances Dilemna
1. Cond. Watts loss 1phase, L-L = 2*[I(line-line)]^2 * R
2. Cond. Watts loss 1phase, L-N = [I(line-neutral)]^2 * R
3. Cond. Watts loss 3phase, = 3*[I(3phase)]^2 * R
where R = Ohms to neutral
Any comments. Thanks
RE: Conductor Resistances and Reactances Dilemna
If you are really looking for conductor losses, rather than voltage drop, they aren't the same thing, just figure out the number of amps in the conductor, square that, and multiply by the resistance of the conductor. Calculate the amps in each phase conductor plus the neutral and calculate the loss in each.
Line to neutral ohms would be the one-way impedance of the conductor.
RE: Conductor Resistances and Reactances Dilemna