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19. PROPERTY, PLANT AND EQUIPMENT (Details 3)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure of detailed information about property, plant and equipment [line items]      
Average annual depreciation rate 3.13% 3.72% 3.14%
Hydroelectric Generation [Member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Average annual depreciation rate 2.83%    
Thermoelectric Generation [Member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Average annual depreciation rate 4.13%    
Wind Power Generation [Member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Average annual depreciation rate 4.87%    
Administration [Member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Average annual depreciation rate 8.29%