The Importance of Realistic Load Modeling in Power System Harmonic Respnance Analysis

Parallel resonances in electrical power systems can considerably increase levels of harmonic voltages, which may lead to a component breakdown. Major capacitive network components, such as shunt capacitors, can significantly change the network harmonic impedance. It is therefore common to perform a harmonic load flow analysis before the installation of these devices. Due to the difficulty of accurate modeling, system loads are often ignored in such assessments. However, this approach can lead to very pessimistic results, possibly leading to unnecessary investments in filtering solutions. This paper presents the results of a harmonic load flow analysis that was performed during the planning of new capacitors in the 110-kV subtransmission network of Helsinki. Different harmonic load models were employed. The results indicate that because of load damping in the network, it is not necessary to have additional harmonic limiting devices with the capacitors.