Types of damages and abnormal modes of operation of electric power systems, diagrams and principles of their relay protection, purpose and action of protection against ground faults in electrical networks, differential, remote and high-frequency protection of electric lines, protection of power transformers, electric motors and busbars, automatic reclosing devices, including frequency, automatic transfer switching, redundancy in case of failure of circuit breakers and emergency control automation, types and principles of control of electrical devices and alarms at substations. Information on microprocessor (digital) relay protection devices is given. For students of institutions of secondary vocational education.