Harmonic assessment on power netwoks — Application to Portuguese distribution grid

LABELEC has developed a method to identify harmonic content and their origin in power networks which has been extensively and successively applied on Portuguese Distribution Grid in sites where harmonics exceeded the standard limits on EDP Distribuição Annual Power Quality Monitoring Program. The developed technique is based on the use of Fourier Series for identifying the amplitude and phase of the harmonic components of the signal. It uses the direction of flow of the harmonic real power, calculated using monitored voltage and current, to identify the direction of flow of the harmonic power and therefore establishes its origin. Three case studies have been selected as an example of the methodology application to Portuguese Distribution Grid: capacitor banks and the 5th harmonic, even harmonics and triplen harmonics in LV systems. In all of them, it has always been clearly identified the harmonics origin.