section 3 Table of mains voltages and frequencies:
.........................Voltage......Frequency
China, Hong Kong, Macau..220..........50
Japan....................110..........East Japan 50 Hz; West Japan 60 Hz (including Nagoya)
Russia...................220..........50
South Korea..............220..........60
Taiwan...................110..........60
United States.....
(ii) mains (adj): "of or relating to utility distribution mains <mains voltage> <mains water>" http://www.merriam-webster.com/dictionary/mains
(iii) main (n): "a pipe, duct, or circuit which carries the combined flow of tributary branches of a utility system"
(b) Setting aside the difference in voltage and frequency of electricity, it just scientifically not feasible. That is why Taiwan proper never tries to supply electricity to an outlying island. For the same reason, I am perplexed why China builds dams to generate electricity in its southwest or Burma. See