General provisions
Article 21
1. The process of merging the individual grid models established in accordance with Article 27 of Regulation (EU) 2015/1222 shall apply when merging the individual grid models into a common grid model for each long-term time frame. No later than six months after the approval of the generation and load data provision methodology for long-term time frames referred to in Article 17 and the common grid model methodology for long-term time frames referred to in Article 18, all TSOs in each capacity calculation region shall jointly develop operational rules for long-term capacity calculation time frames supplementing the rules defined for the operation to merge the individual grid models pursuant to Article 27 of Regulation (EU) 2015/1222. 2. The coordinated capacity calculators established in Article 27 of Regulation (EU) 2015/1222 shall calculate long-term cross-zonal capacities for their capacity calculation region. For this purpose, no later than six months after the approval of the capacity calculation methodology for long-term time frames referred to in Article 10, all TSOs in each capacity calculation region shall jointly develop operational rules for long-term capacity calculation time frames supplementing the rules defined for the operation of the coordinated capacity calculators pursuant to Article 27 of Regulation (EU) 2015/1222. 3. The relevant requirements set in Article 27 of Regulation (EU) 2015/1222 shall apply for long-term capacity calculation time frames.