The main reason why dc cannot be used is that it cannot be stepped up as Ac using transformers.
When transmitting either ac or dc, there exist losses(dc losses is higher though in short distance). Assuming the consumers end has been reached and the remaining voltage is low, we can use transformer to boost the low voltage if it is ac; but if it is dc, nothing can be done
Well done @greenrun
Please can you reread your reply and make some corrections, on the first part of your comment, as I cannot clearly understand what you mean.
DC losses is higher in short distance transmission. At longer distance, DC beats AC. Thank you.
Corrected
I had 1% battery remaining after reading this post last night, so i typed the comment quickly.
A DC converter station can be step up DC to a very high voltage, up to 1100KV as evidenced by the new ultra-high voltage direct current (UHVDC) transmission using Siemens Transformer. The only issue is that DC is not economical for short distance transmission,i.e. distances shorter than 600KM, at distances greater than 600KM, the AC losses increases so much that a DC setup becomes more efficient.
Ooooh
That should be an improvement in technology
I know from farday's law, flux must exist for a transformer to work
And dc got no flux