The rapid penetration of wind and solar generation in the Brazilian Interconnected System has shifted the role of transmission: lines feeding the renewable-rich Northeast and South corridors toward the Southeast load centre have become the binding constraint on the financial viability of variable renewable energy. Their failures translate increasingly into curtailment of wind and solar generation, measurable welfare losses, redispatch and ancillary-service costs, and contractual exposures under the concession regime. This study develops an integrated economic framework that quantifies, exclusively from public-domain data, the joint cost of energy not served (valued by three complementary methods), the Variable Parcel imposed by Brazilian regulation, the redispatch triggered by the contingency, and the curtailed renewable energy that would otherwise have flowed through the affected corridor.

Line availability is modelled as a two-state alternating process with stationary failure and restoration distributions calibrated from perturbation disclosures published by the national system operator. Renewable curtailment is computed as the difference between unrestricted dispatch and the dispatch feasible after the contingency, using daily-resolution wind and solar generation profiles obtained from plant-level public series. Inputs include the regulator's tariff and concession data, the system operator's perturbation and dispatch records, the planning agency's deficit cost, the clearinghouse's settlement prices and public renewable generation series; no proprietary or confidential data are used. Costs are aggregated through a twenty-five-year Monte Carlo simulation with ten thousand trajectories under the regulatory cost of capital. Corrective, preventive and predictive maintenance strategies are compared on net present value, internal rate of return, discounted payback and life cycle cost.

Predictive maintenance is shown to dominate the alternatives on lines that feed renewable corridors, with net present value gains above fifteen per cent under the regulatory cost of capital; the share of curtailed renewable energy in total economic loss is sizeable and largely absent from current official valuations of energy not served; divergence among the three valuation methods produces a meaningful uncertainty band that should be reported alongside any single-point estimate of reliability cost.

The framework offers transmission concessionaires, the regulator and the system operator a quantitative basis to incorporate variable renewable curtailment into reliability and regulatory decisions, supporting revision of the Brazilian penalty mechanism and the design of expansion auctions in renewable-dense corridors.