The fractional frequency transmission system FFTS is a very promising long -distance transmission approach, which uses lower frequency (50/3) to reduce the electrical length of the AC power line, and thus its transmission capacity can be increased several fold .   This paper introduces the primary experiments results of FFTS. 
 
The experiment uses the phase-controlled cycloconverter as the frequency changer, stepping up 50/3Hz electricity to 50Hz   electricity and supplying it to the utility grid. Thus, a new flexible ac transmission system device is successfully established   in this experiment. The synchronizing process of 50/3Hz transmission   system   with 50Hz utility system is introduced   in this paper. The experiment results   show that a 1200km/500kv transmission   line can transmit more than 2000MW electric power when employing the FFTS. The experiment also illustrates   that there is no essential difficulty   to realize FFTS in engineering practice.