Individual Grid Models and Common Grid Model
The common grid model methodology (CGMM) defines an Individual grid model (IGM) as "a data set describing power system characteristics (generation, load and grid topology) and related rules to change these characteristics during capacity calculation, prepared by the responsible TSOs". These IGMs, one for each control area, are then combined into a common grid model (CGM) which the CGMM defines as "a Union-wide data set agreed between various TSOs describing the main characteristic of the power system…"
The main purpose of this service is to provide a common data model representing the power system in the Nordic and Pan-European area, which can be used for performing further analysis through the other services performed by the Nordic RSC, in order to ensure a secure power market and security of supply.
The CGMs are created for different time horizons from a near real time representation of the grid, to one and two days ahead, and all the way up to year ahead models. The different time horizons have different purposes and provide input data for different services.
When the TSOs build IGMs for the different time horizons they ensure that the model represents the real power system as closely as possible. They make sure that the equipment model is up to date and they incorporate topological changes during the different period by applying an outage plan. The TSOs then use forecasts for load, consumption, net position in each bidding zone and the flow on the different DC lines to ensure that the flow in the grid is as accurate as possible.
The service at the RSC starts when the individual grid models (IGMs) are received from the TSOs. The IGMs are imported to the CGM System, where the RSC is validating that the models are following a set of rules about the modelling and convergence behavior of the IGMs. In case IGMs are missing, invalid or do not converge in terms of power flow calculation, the RSC will follow defined issue resolution and fallback procedures. After having merged the IGMs into a CGM the model is again validated in order to ensure that it is can be used for the subsequent business processes. Finally, the CGM is made available for the TSOs as well as the services at the Nordic RSC using the CGM as input data.
Today the CGM service is being implemented on Nordic level where the Nordic TSOs send their IGMs directly to Nordic RSC. The current work is on improving the quality, reliability and trustworthiness of the models, followed by the implementation of the D-1, D-2 and ID business process. However, this process will eventually be a pan-European process where all European TSOs send their IGMs to a central system (OPDE) and one RSC is responsible for creating the full pan-European CGM. The process of defining that process and designing and creating the system is ongoing and is coordinated by ENTSO-E.
See the video below for a basic explanation of the service provided by ENTSO-E and Coreso.