The Grid Code is the technical document which establishes the rules governing the operation, maintenance and development of the transmission system and sets out the procedures for governing the actions of all transmission system users. The document ensures that all users are treated in a transparent and equitable manner. For the purposes of the Grid Code, a user is defined as any party using or planning to use the transmission system.
Units that are controlled by EirGrid are required to comply with technical rules in the Grid Code. When a unit connects for the first time, makes changes or returns from maintenance, they test the performance of the unit. These tests are witnessed by EirGrid.