These standards outline guidelines and requirements for relay protection systems used in renewable energy systems. tries but also emerging countries such as China. Moreover, the advantages of photovoltaic panels are numerous, both in terms of duration of the installation and in. Modern solar photovoltaic (PV) power plants typically generate electricity at low voltages, ranging from 400V to 800V. To efficiently export this electricity to the utility grid, the generated voltage must be stepped up to medium or high voltage levels—such as 11kV, 33kV, 66kV, or 132kV—depending. An Introduction to Protective Relays for Solar-Plus-Storage Systems Electrical relays, protective devices used to switch power on or off for parts of a circuit, have been integrated into circuits for nearly two hundred years. The first example of a relay dates back to the mid-nineteenth century. aic installations on top of buildings within the European Uni n. These requirements come, for example, from bui ding insurers, the local fire. The recommendations and guidelines in this document are based on the experience and judgment of WECC members and include criteria for developing protection system best practices that, when implemented and used consistently, result in dependable, secure protection systems.