Gentlemen I have an installation where i have a 125Amp MCCB to a 50Kva transformer. My cable size is 35MM. The distance of the conductor is approximately 300 feet. My question is. Is the 35MM(2/0 conductor of the right size for the distance of the cable run. Insight will be most appreciated.
Reasoning: while tables do vary, we can safely assume that the rating of copper wires is roughly the same around the world. According to the Austrian table, 35 mm2 is only good for 119 amps if there are three current carrying conductors (i.e. a 3-phase system, the neutral is not considered a current-carrying conductor in this case, only in single phase applications) and at 30° C ambient temperature. At 25° C we can go up to 128 amps but considering you're in Kuwait I seriously doubt you would get by without exceeding that temperature even if the cable is run underground. Sooo, even without doing any voltage drop calcs it's at the very best borderline.
I quickly did an online voltage drop calculation and that read 1.9%. Way too much for a main feeder, you'd want more like 0.5% for anything close to European standards (most European countries specify no more than 4% in the entire fixed installation).
Unless this is a "make do" situation definitely upgrade to 50 mm2 or downgrade to 100 A or smaller MCCB (and even that results in a rather bad 1.5% voltage drop).
Thanks for the insight. The cable is rated to 50cecius. Originally I wanted to use a 30Kva transformer but out here it is near impossible to locally find step dowen transformers from british to american voltage. Again thank you.