Grid Codes of Transmissions System Operators (TSO) put large demands on the currently installed Wind Power Plants (WPPs). Nowadays WPP are treated similarly as conventional power stations. They should work even if operating conditions deviate from nominal values, e.g. when during a fault the voltage at the connection bus drops nearly to zero. The paper describes grid codes distinguishing requirements of active and reactive power generation and Fault Ride Through characteristics. Among the described standards Polish, German and Danish and in some cases British and Norwegian requirements are mentioned. The differences between the standards are reviewed and are referenced to Polish grid regulations. Discussion supplements certain results of the laboratory research.