K-Factor can be a Misleading Power Quality Indicator

This paper looks at the evolution and measure of success of different harmonic treatments applied in commercial buildings. Typical levels of voltage distortion are described in light of extensive harmonic data collection at North American sites over several years at hundreds of electrical panels and transformers. The field data shows that contrary to the popular belief, doubling the neutral and derating or k-rating the transformer does not properly address the harmonic issues facing today’s buildings. Voltage distortion often exceeded the 5% recommended limit set out in section 6.6 of IEEE Std 519-1992. A case study is presented that documents voltage distortion levels in a typical commercial high rise building, and the effectiveness of different transformer configurations in reducing these harmonic levels are evaluated.