Methodology used to calculate technical capacity

The valid Regulation (EC) No 715/2009 of the European Parliament and of the Council stipulates the following: “The transmission system operator shall make public detailed and comprehensive description of the methodology and the procedure, including the parameters and the main assumptions, used for calculate technical capacity“.  

Technical capacity - definition and explanation 
Definition by the Regulation (EC) No 715/2009 of the European Parliament and of the Council: “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“.
At determining maximum technical capacity, technical possibilities of all important system components relevant for the hydraulic calculations, network configuration, expected gas composition and operational marginal conditions are taken into account.
Technical capacity of each entry point and exit depends on the following: Level of simultaneous use of capacities of other entry and exit points at the same part of the system

Calculation methodology
SIMONE programme package for the hydraulic simulations of transmission system has been used for calculating technical capacities. All current physical parameters of the gas pipeline and the transmission system plants make topology of SIMONE model of the transmission network for the entries and exits for which technical capacities have been calculated. SIMONE software is widely used computer tool for analyzing flow of gas through a transmission system.

The simulations are based on non-linear partial differential equations which describe mass preservation, momentum and energy. The behaviour of the real gas is described by the equation of state which includes the real gas composition. The pressure drop caused by the flow resistance is calculated by the use of friction factor which depends on the roughness of a pipeline wall, pipeline diameter, flow velocity and the characteristics of a gas composition.

Main parameters
Assumptions for the simulation scenarios Calculation procedure

In compliance with the mentioned parameters and assumptions the worst-case scenarios of transmission are made and in that way are determined the maximum flow amounts for the each entry and exit point achievable in all entry and exit combinations by taking into account necessary pressure conditions at the takeover points as well as requirements regarding security and efficiency of the system. 
The simulations which meet the criterion regarding pressure and flow at all entry and exit points are considered to be referential for determining technical capacity.

The result of methodology application is the amount of technical capacity for which the transmission system operator can guarantee that it will always be achieved at regular operating conditions and which is offered for allocation as a firm capacity.

Transmission system entry/exit capacity within the borders of the Republic of Croatia has been expressed in the Preliminary connection approval issued to the owners of associated systems and plants.
For border interconnections technical capacity is determined in cooperation with the neighbouring transmission system operator and defined by an Interconnection Agreement.

Data publication

Plinacro have published information on the technical entry/exit capacities of the transmission system on its web site