CALCULATION OF THE N – 1 FORMULA

The N – 1 formula describes the ability of the technical capacity of the gas infrastructure to satisfy total gas demand in the calculated area in the event of disruption of the single largest gas infrastructure during a day of exceptionally high gas demand occurring with a statistical probability of once in 20 years. Gas infrastructure includes the gas transmission network including interconnectors as well as production, LNG and storage facilities connected to the calculated area. The technical capacity According to Article 2(1)(18) of Regulation (EC) No 715/2009, ‘technical capacity’ means the maximum firm capacity that the transmission system operator can offer to the network users, taking account of system integrity and the operational requirements of the transmission network. of all remaining available gas infrastructure in the event of disruption of the single largest gas infrastructure should be at least equal to the sum of the total daily gas demand of the calculated area during a day of exceptionally high gas demand occurring with a statistical probability of once in 20 years. The results of the N – 1 formula, as calculated below, should at least equal 100 %. N – 1% = (EP_(m) + P_(m) + S_(m) + LNG_(m) – I_(m) / D_(max)) × 100, N – 1 ≥ 100 % ‘Calculated area’ means a geographical area for which the N – 1 formula is calculated, as determined by the Competent Authority. ‘D_(max)’ means the total daily gas demand (in mcm/d) of the calculated area during a day of exceptionally high gas demand occurring with a statistical probability of once in 20 years. ‘EP_(m)’: technical capacity of entry points (in mcm/d), other than production, LNG and storage facilities covered by P_(m), S_(m) and LNG_(m), means the sum of the technical capacity of all border entry points capable of supplying gas to the calculated area. ‘P_(m)’: maximal technical production capability (in mcm/d) means the sum of the maximal technical daily production capability of all gas production facilities which can be delivered to the entry points in the calculated area. ‘S_(m)’: maximal technical storage deliverability (in mcm/d) means the sum of the maximal technical daily withdrawal capacity of all storage facilities which can be delivered to the entry points of the calculated area, taking into account their respective physical characteristics. ‘LNG_(m)’: maximal technical LNG facility capacity (in mcm/d) means the sum of the maximal technical daily send-out capacities at all LNG facilities in the calculated area, taking into account critical elements like offloading, ancillary services, temporary storage and re-gasification of LNG as well as technical send-out capacity to the system. ‘I_(m)’ means the technical capacity of the single largest gas infrastructure (in mcm/d) with the highest capacity to supply the calculated area. When several gas infrastructures are connected to a common upstream or downstream gas infrastructure and cannot be separately operated, they shall be considered as one single gas infrastructure. N – 1% = (EP_(m) + P_(m) + S_(m) + LNG_(m) – I_(m) / D_(max) – D_(eff)) × 100, N – 1 ≥ 100 % ‘D_(eff)’ means the part (in mcm/d) of D_(max) that in case of a supply disruption can be sufficiently and timely covered with market-based demand-side measures in accordance with Article 5(1)(b) and Article 6(2). The calculated area referred to in point 3 shall be extended to the appropriate regional level where applicable, as determined by the Competent Authorities of the Member States concerned. For the calculation of the N – 1 formula at regional level, the single largest gas infrastructure of common interest shall be used. The single largest gas infrastructure of common interest to a region is the largest gas infrastructure in the region that directly or indirectly contributes to the supply of gas to the Member States of that region and shall be defined in the joint Preventive Action Plan. The regional N – 1 calculation can only replace the national N – 1 calculation, where the single largest gas infrastructure of common interest is of major importance for the gas supply of all Member States concerned according to the joint risk assessment.

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Source: EUR-Lex (Cellar) · retrieved 2026-11-04 · Text as adopted (Official Journal); later amendments are not incorporated in this text.