Influence of the ground impedance on the earth fault current calculation in lengthy electrical networks containing harmonic sources

The influence of the earth impedance on the harmonic earth fault current in a lengthy 110 kV supply network (total length over 7700 km, galvanic connected, neutral earthed by Petersen coils) will be shown in the paper. It will be pointed out that the earth impedance can be correctly considered by means of the implementation of the harmonic network equivalent impedance into the computation model. A practical approach of harmonic network impedance determination on the base of long-time current and voltage measurements at the network node is described in the paper.