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Capacity Calculation

Description of the methodology to calculate the technical capacity to meet point 3.1.2. lit m) of EU Regulation 715/2009

The calculation of the technical capacity of the ONTRAS grid is executed at least once a year based on the existing network and existing technical and contractual framework parameters.

The contractual framework parameters include the minimum and maximum pressures and capacities agreed upon with adjacent network operators and consumers directly connected to the ONTRAS grid. The technical framework parameters include pipeline properties such as diameter, pressure level, and pipe roughness, as well as performance parameters of compressor stations and other facilities such as gas pressure, control, and measurement systems (GDRMA).

To calculate the technical capacity of the ONTRAS grid, the existing pipeline system is divided into individual pipeline sections. Pipeline sections are pipe segments with consistent attributes along their total length, such as diameter. They begin or end at attribute changes and at each branching pipeline section. This process creates a network model consisting of pipelines and all relevant facilities, including compressor stations. In this network model, the volume flow and pressure loss in each pipeline section are calculated under various load scenarios, while adhering to the first and second Kirchhoff’s laws using an iterative approximation method.

During the regular calculation of the capacity model at the beginning of each year, different load flow scenarios are considered. This includes varying the withdrawal quantities of exit points based on temperature and comparing different uses of entry points. Requests for additional capacity during the year are evaluated using the current network model and relevant load flow scenarios.

If the contractual and technical conditions are not violated under various load flow scenarios, the technical capacity at the entry and exit points can be designated and marketed as firm Freely allocable capacity (FZK). However, if contractual or technical conditions are violated, it is necessary to either reduce FZK at an appropriate location or designate the requested capacity as Dynamically allocable capacity (DZK) or Conditional firm freely allocable capacity (bfzK).

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