Hi,

Want to size the cable for a load of 2000kW feeder, I assumed that the pf is 0.8 and efficiency is 0.85 and the voltage is 690V, 50 Hz. 3 ph.

I got

1000 × 2000 / 1.73 × 690 × 0.8 × 0.85 = 2461.00A

I always thought the using 9 runs of 1c x 150 sq.mm would be sufficient as the derated current for this cable is 293 (Actual vendor's cable rated current was 367A)

9 runs I got becos 2461/293 = 8.4 runs.

In this case it happens that i get 9 runs when I used single core so I can terminate easily 3 runs per phase. Suppose I had got 10 run, I guess I should use 12 runs of single core. Is this correct?

Now what is the difference if I use 3C or 1C. I always thought same size sq.mm cable whether 3c or 1c has the same CONDUCTOR (that is only same copper cross-section area) cross-section. Is this correct? for example a 240mm2, 3 core cable and 240mm2 1C cable has the same conductor size.

But if I use 3 core x 150 sq.mm in the above, now the cable derated current is only 205A (Actual vendor cable rated current is 257A). So I would require 2461/205 = 12 runs of 3c x 150 sq.mm.

I understand that voltage drop and short circuit calculations also have to be done. But pls clarify my above basic query. Thanks

## Comments rated to be "almost" Good Answers:

Re: Single Core or 3 Core - Why ?" by BabyGuinness on 02/07/2008 3:03 PM (score 1)