EN 50550: This standard applies to power frequency overvoltage protection devices (POPs) designed for household and similar applications, operating at 50 Hz with a rated voltage of 230 V AC. It specifies the requirements for POPs used with main protective devices like circuit breakers, residual current circuit breakers, or residual current circuit breakers with overcurrent protection. POPs are intended to protect equipment from overvoltages caused by issues such as loss of the neutral conductor by triggering the main protective device. The standard includes definitions, classifications, characteristics, marking requirements, and testing conditions for POPs. It does not cover surge protective devices or protection against common mode overvoltages.