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3. PRINCIPLES OF CONSOLIDATION (Details) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Cemig Geracao E Transmissao [member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Form of valuation |  | Consolidation | Consolidation
Percentage of ownership in subsidiary direct interest |  | 100.00% | 100.00%
Percentage of ownership in subsidiary indirect interest |  |  |
Cemig Distribuicao SA [member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Form of valuation |  | Consolidation | Consolidation
Percentage of ownership in subsidiary direct interest |  | 100.00% | 100.00%
Percentage of ownership in subsidiary indirect interest |  |  |
Gasmig [member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Form of valuation |  | Consolidation | Consolidation
Percentage of ownership in subsidiary direct interest |  | 99.57% | 99.57%
Percentage of ownership in subsidiary indirect interest |  |  |
Cemig Geracao Distribuida (Usina Termica Ipatinga) [member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Form of valuation | [1] | Consolidation | Consolidation
Percentage of ownership in subsidiary direct interest | [1] | 100.00% | 100.00%
Percentage of ownership in subsidiary indirect interest |  |  |
Cemig Sim (Efficientia) [member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Form of valuation | [2] | Consolidation | Consolidation
Percentage of ownership in subsidiary direct interest | [2] | 100.00% | 100.00%
Percentage of ownership in subsidiary indirect interest |  |  |
Centroeste [member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Form of valuation | [3] | Consolidation | Equity method
Percentage of ownership in subsidiary direct interest | [3] | 100.00% | 51.00%
Percentage of ownership in subsidiary indirect interest |  |  |
[1] | On October 19, 2020, an Extraordinary General Meeting of Shareholders approved the merger of this wholly-owned subsidiary, at book value, and as a result the investee ceased to exist and the Company took over of all its rights and liabilities.
[2] | On April 14, 2020, the Annual Shareholders General Meeting decided to change this subsidiary's By-laws, changing the name of this subsidiary to Cemig Solucoes Inteligentes em Energia S.A.-Cemig Sim.
[3] | On January 13, 2020, the Company concluded acquisition of the equity interest of 49% of the share capital held by Eletrobras in Centroeste, resulting in its now holding 100% of that investee. More details see notes 1 and 16.

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