This publication provides introductory technical guidance for electrical engineers interested in relays and controls for electrical distribution systems. Here is what is discussed: 1. RELAY FUNCTIONS 2. RELAY FUNDAMENTALS 3. RELAY CONSTRUCTION 4. RELAY MAINTENANCE PERIODS 5. RELAY GENERAL FIELD INSPECTION 6. RELAY PERFORMANCE TESTS 7. COMMON ELECTROMECHANICAL RELAY TESTS 8. RELAY TEST EQUIPMENT 9. RELAY REPAIRS 10. CONTROL FUNCTIONS 11. PREVENTIVE MAINTENANCE AND INSPECTIONS OF CONTROLS 12. TROUBLESHOOTING CONTROLS.