Power Quality

Four steps to reduce harmonic distortion

Electrical engineers should follow these four steps when designing for high-quality power systems

By Nick Holway, PE, CDM Smith, Boston September 13, 2019
  1. Preliminary harmonics study. Model the network and loads using power system analysis software. Calculate short circuit and maximum demand. Establish the point of common coupling and analyze harmonic distortion.
  2. Design development. Review the results of the harmonic analysis. Determine the need for additional harmonic mitigation. Determine the impact of harmonics on sources of standby power. Design and specify products to mitigate distortion. Specify performance testing procedures to measure distortion during project startup. Consider including power monitoring devices and systems to allow for nonintrusive performance testing. Memorialize the harmonic analysis by revising the model to include mitigation equipment. Document the results of the preliminary harmonic study before procurement or the bid phase. There are many methods to reduce harmonic distortion within a system. A wide range of products are available to engineers and end users. Several products with advantages and disadvantages are listed in Table 1 to provide guidance. 
  3. Final harmonic study. Incorporate as-built conditions into the model. Review results of the final analysis with respect to performance requirements. Recommend additional harmonic mitigation equipment if as-built conditions have introduced additional challenges. Consider specifying an independent third-party analysis for projects where a conflict of interest is a concern.
  4. Performance testing. Measure values in compliance with the latest standard of IEEE Standard 519. Specify testing procedures to reflect worst-case operating scenarios. Coordinate performance testing procedures with the owner to avoid surprises or impacts to operation. Review results for compliance with performance criteria. Discuss unexpected test results with all stakeholders and evaluate if additional engineering, analysis or testing is needed to provide a reliable system. Document test results as benchmarks for future projects. 

Nick Holway, PE, CDM Smith, Boston
Author Bio: Nick Holway is a senior electrical engineer at CDM Smith with more than 10 years of experience working in the electrical engineering field, providing design, engineering and construction support of power systems for municipal, industrial and private clients.