What is rated power, rated voltage and currency？What is relationship between them？ 

Rated power (pe) refers to the maximum active power that the generator can output under the rated operation conditions, and its unit is kilowatt (Kw) or megawatt (Mv). 
Rated voltage (Ue) refers to the line voltage when the generator is in normal operation, and its unit is volt (V) or kilovolt (Kv). 
Rated current (Ie) refers to line current when the generator is under rated operation conditions, and its unit is ampere (A) or kilo-ampere (KA). 
Rated power= rated voltage × rated current