What is the grid code?

The grid code, also known as the transmission code in some countries, is the set of rules a transmission system operator (TSO) uses to define conditions for accessing the electricity grid.

Role of the grid code

The grid code regulates the general conditions pertaining to how installations connect to the high and extra-high voltage grid. The code also covers grid usage, system services, grid expansion, and general grid operation. Depending on the country, conditions for the grid at the low-voltage or distribution level are fixed separately (often in a distribution code). The rules of the grid code apply to all systems that feed into the grid control network, from a large power plant producing several hundred megawatts to a solar plant producing just 500 kW. Among other things, the grid code defines specific conditions that must be met for plants to receive pre-qualification and participate in providing grid frequency measures. Ciaran Roberts provides a good overview of the varying international grid code regulations in a document written for the Lawrence Berkeley National Laboratory (funded by the US Energy Regulatory Commission, Office of Electric Reliability).