Firm

There are two definitions of firm capacity, one for consumption and one for generation: 

Permitted consumption capacity: The maximum capacity specified in the connection agreement for electrical installations concluded between the TSO or DSO and the network user, in the ownership boundary act and/or other documents related to the network user’s electrical installations, which the network user may consume from the electricity networks at any time. 

Permitted generation capacity: The maximum active power that may be supplied from the network user’s electrical installations to the TSO’s or DSO’s electricity networks at the connection point, as specified in the connection agreement for electrical installations concluded between the TSO or DSO and the network user, in the ownership boundary act and/or other documents related to the network user’s electrical installations. At present, the impact of consumers’ capacity on the distribution electricity network is assessed using theoretical calculations, as regulated in the methodology for determining calculated electrical loads - link to methodology for Determining Consumers’ Calculated Electrical Loads, in Lithuanian only: https://www.e-tar.lt/portal/de/legalAct/ca6c23a0f1fc11ec8fa7d02a65c371ad. The distribution network is developed based on assumptions, taking into account the diversity factors of certain consumer groups (apartments in multi-apartment buildings, homesteads, residential houses), determining the normative capacities of facilities, and considering the impact of heat pumps and EV charging stations on the distribution network

Two terms for non-firm capacity are considered: flexible connection agreement and variable capacity. 

Flexible capacity is understood in the context of flexible connection agreements as outlined in Directive (EU) 2024/1711. 

Flexible capacity is interpreted as capacity provided under special network use terms. 

These terms may vary and depend on whether the capacity is needed for consumption or generation, as well as on the user and the size and nature of the required capacity. When referred to generation, flexible capacity is treated as the available network capability to accept generation during periods that do not coincide with the solar generation profile. When referred to consumption capacity, two scenarios are distinguished:

• Available network capacity during periods that do not coincide with the peak consumption profile. Peak consumption is determined by the actual load of the substation and may differ depending on the substation to which the user is connected.
• If the user’s needs require steady capacity in all periods (even if temporarily lower), then we treat flexible capacity as connecting the user in N-0 mode, with the connection agreement specifying conditions regarding possible restrictions and more frequent disconnections from the network during network maintenance. Such a user connection would be exclusively temporary until the end of the substation reconstruction, when it will be possible to switch the user to N-1 mode.

Variable capacity differs from flexible capacity in two main ways. First, it is not a temporary arrangement – the object always operates under this agreement. Second, there are no predefined capacity limits for specific time periods. Instead, the object must continuously adapt to the actual grid load, without exceeding its maximum permitted capacity. At present, these objects are directly connected to the transformer via fiber optic cables, enabling them to follow real-time data. This setup allows only one variable connection per transformer. In the long run, we plan to integrate DERMS solutions to connect multiple objects simultaneously

For flexible connection agreement capacity, historical 15-minute net load data for substations and secondary substations are used. Substation and secondary substation loads are checked across different seasons – for example, in winter when consumption is highest and in summer when generation is highest. From the analysis results, peak and off-peak periods are identified, and the actual load is assessed. In addition, expected loads are added for users that have been issued connection permission but are not yet connected. To manage the risks, a load margin is maintained. For variable capacity, no fixed methodology exists, as the object must continuously adjust its consumption or generation in real time based on the grid load.

As per the answer provided in the description of the methodology leading to firm capacity results, following is the link to the methodology for determining consumers’ calculated electrical loads (in Lithuanian only): https://www.e-tar.lt/portal/de/legalAct/ca6c23a0f1fc11ec8fa7d02a65c371ad

Currently, the impact of consumers’ capacity on the distribution electricity network is assessed using theoretical calculations, as regulated in the methodology for determining calculated electrical loads. The distribution network is developed based on assumptions, taking into account the diversity factors of certain consumer groups (apartments in multi-apartment buildings, homesteads, residential houses), determining the normative capacities of facilities, and considering the impact of heat pumps and EV charging stations on the distribution network