Introductory technical guidance for electrical engineers interested in harmonics in electric power distribution systems. Here is what is discussed:1. HARMONICS DEFINED2. HARMONIC SOURCES3. HARMONIC TECHNICAL HISTORY4. RESONANCE5. ELECTRICAL LOADS6. NEUTRAL CURRENTS7. DERATING POWER EQUIPMENT8. GENERATOR CONTROL PROBLEMS9. UPS OUTPUT HARMONIC DISTORTION10. AC SYSTEM RESPONSE TO HARMONICS11. SOLUTION OF HARMONIC PROBLEMS12. MEASUREMENT OF NON-SINUSOIDAL CURRENTS AND VOLTAGES13. CONCLUSIONS.