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15. CONCESSION CONTRACT ASSETS (Details Narrative) - BRL (R$) R$ / shares in Units, R$ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Disclosure of assets recognised from costs to obtain or fulfil contracts with customers [line items] |  |  |  |
Borrowing costs capitalised | R$ 34 |  |  |
Impairment on assets | 14 | R$ 22 |  |
Contract assets | R$ 4,980 |  |  |
Periodic Tariff Revision of Permitted Annual Revenue |  | 9.13% |  |
Increase in revenues | 13.15% |  |  |
NET REVENUE | R$ 25,228 | R$ 25,487 | [1] | R$ 22,266
Assets | 54,083 | R$ 50,526 | [1] | R$ 59,855
Basic Network of the Existing System (BNES) [member] |  |  |  |
Disclosure of assets recognised from costs to obtain or fulfil contracts with customers [line items] |  |  |  |
Assets | R$ 207 |  |  |
Percentage of changes in the asset base | 7.00% |  |  |
Percentage of account write-offs and assets | 38.00% |  |  |
Basic Network of New Facilities (BNNF) [member] |  |  |  |
Disclosure of assets recognised from costs to obtain or fulfil contracts with customers [line items] |  |  |  |
Assets | R$ 321 |  |  |
Net of PIS/Pasep and Cofins taxes | 502 |  |  |
contract 006/1997 [member] |  |  |  |
Disclosure of assets recognised from costs to obtain or fulfil contracts with customers [line items] |  |  |  |
NET REVENUE | R$ 528 |  |  |
Amounts reclassified | R$ 1,296 | R$ 1,281 |  |
contract 079/2020 [member] |  |  |  |
Disclosure of assets recognised from costs to obtain or fulfil contracts with customers [line items] |  |  |  |
NET REVENUE | R$ 23 |  |  |
Repositioning factor | 57.50% |  |  |
Commercial operation | R$ 24 |  |  |
contract 079/2020 [member] | Bottom Of Range [member] |  |  |  |
Disclosure of assets recognised from costs to obtain or fulfil contracts with customers [line items] |  |  |  |
Weighted average cost of capital after tax | 6.64% |  |  |
contract 079/2020 [member] | Top of Range [member] |  |  |  |
Disclosure of assets recognised from costs to obtain or fulfil contracts with customers [line items] |  |  |  |
Weighted average cost of capital after tax | 7.71% |  |  |
[1] | See note 2.8.

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