Analysis of active powers of non-linear loads connected to the high voltage network

The paper presents the results of an analysis of active powers at the nodes connecting the 220 kV supply network to three large-capacity nonlinear loads: an aluminum smelter shop, a paper mill and a traction substation. These facilities have different load curves. The load of the aluminum smelter shop remains virtually invariable. The paper mill load changes during the day time because of shift work. The load of the traction substation is abruptly variable. The main electrical equipment of the facilities is the source of harmonics. The measurements of currents and voltages were used to calculate active power for harmonics 2-40. The calculations show that although the facilities are the sources of harmonics and generate harmonic active powers to the supply network they also receive harmonic active powers from the supply network. During the measurements, the harmonic active powers change the flow directions. Their values change in a wide range and can reach several tens of kilowatts.