Harmonics and system natural frequencies

High harmonic contents in power distribution systems are usually due to system resonances at harmonic frequencies. This paper investigates harmonic resonance related problems under various system operating conditions using an accurate computer model. Three harmonic reduction methods are examined to observe their effectiveness. These methods are installation of harmonic filters, harmonic cancellation by the /spl Delta///spl Delta/ and /spl Delta//Y transformer configuration, and low voltage capacitor resizing. To demonstrate these applications, an actual industrial distribution system with field harmonic measurements is presented. The results of the case study are also presented.