Validated & Verified voltage-drop example

[ramsy]

I have asked the member who posted this voltage drop example below to confirm it was created using ETAP, validated and verified (V&V) against IEEE and several other standards.

Assuming 480V, 400A, 750ft, pf= 0.85, above ground installation of magnetic conduit, and limiting VD = 2%

(1 set) 1/C 600 KCMIL = 5.3% VD
(2 set) 1/C 600 KCMIL = 2.6% VD
(3 set) 1/C 500 KCMIL = 1.8% VD

if installation is underground duct, using PVC, then;

(2 set) 1/C 500 KCMIL = 2.4% VD
(3 set) 1/C 350 KCMIL = 2.0% VD

Me and Smart $ had comparative results using formulas from Note #2 of NEC Table 8 & 9, but my results only match the V&V example above using 420 Amps rather than the 400 provided.

I suspect this ETAP example has done something important to the amperage, which me and Smart are both missing. Could this I = (Watts / Phases / L-to-N voltage) have something to do with it.

 

[kingpb]

The calculations were done using the load flow module of ETAP. The load is comprised of 80% motor, and 20% static. Cable is installed as U/G buried (non-duct bank) operating at maximum 75 deg C. Branch losses are S= 4.8kw + j5kVar.

I would curious to know what numbers your getting, so I can then try and see where the difference is occurring.

 

[ramsy]

I haven't compensated for mixed loads or branch losses (ie) S= 4.8kw + j5kVar. My numbers are:
Using 480v, 400A 3?, 750ft, #600cu, Pf = 0.85, ferrous conduit @ 21c ambient gets me:
I-Load = 400A (Not Pf adjusted), Z = 0.03464, Op.Temp = 69.9c, Volts dropped = 24, or 5%