The book describes the principles of operation and maintenance of the most common relay protection devices and electrical automation of secondary and signal chains of power plants and substations. Operations with relay protection and automation in the production of various switching in primary chains are considered . The first edition was published in !976 g. The book is intended for operational personnel of power plants and substations and mobile operational teams, it can be useful for personnel of RZAI services for training of operational personnel, as well as for students of PTU of relevant specialization .