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20 Accounts payable to suppliers (Tables)
 12 Months Ended
Dec. 31, 2020
Accounts Payable To Suppliers [Abstract]  
Schedule of accounts payable to suppliers
  12.31.2020 12.31.2019
Energy supplies  1,393,899  1,085,777
Materials and supplies 671,458 520,647
Natural gas for resale  38,574 79,174
Charges for use of grid system 332,521 187,595
   2,436,452  1,873,193
Current  2,291,307  1,685,280
Noncurrent 145,145 187,913