This article discusses windfarm electrical power system issues in grid codes. Grid codes are published by utilities and system operators to define the requirements for the interconnection of generation and other facilities to the grid. The purpose of the grid code requirements is to ensure reliability, stability, power quality, protection of equipment, and worker safety. These requirements are given at the point of interconnection (POI) with the transmission or distribution system and are different depending on the sizes and types of generation. Grid codes can cover a broad range of requirements, from continuous operational constraints to behavior during contingencies such as faults, and they vary considerably based on the issuer, their country or region, and the type of transmission or distribution system. Manufacturer specifications for wind turbines are generally given on a per-turbine basis at the collector system voltage. When a wind farm is proposed, an initial assessment is made of the suitability of the wind turbines to the system. Studies that evaluate system performance and conformance with the grid code are performed of the grid and wind farm(s) being considered. Finally, tests and measurements during and after commissioning verify conformance of the wind farm to the applicable grid code.