The converter for dynamic reactive power compensation KONTRAC PN225AC is produced by Končar – Electronics and Informatics, Inc. and is built in traction substations 25 kV, 50 Hz. The rated power of the converter is 225 kvar and a response of the converter to step change of rated reactive power is less than few periods of the supply voltage main harmonic. The converter is therefore able to compensate reactive power practically continuous in a range from 225 kvar inductive to 225 kvar capacitive. In traction substations overall reactive power for compensation can be adjusted either by installation of appropriate number of the converters which are connected in parallel or a combination of the parallel connected converters and the facility with fixed reactive power compensation can be used. In this way reactive power of the traction substation can be compensated but without excessive reactive power and associated costs. In the paper are presented overall costs of electrical energy for electric traction in Croatia in few past years and an influence of electric railway system on power quality in transmission system is briefly described. A description of the converter comprises work principle, technical data and measurement results which were made in laboratory and in traction substation. Namely, the facility with fixed reactive power compensation and two converters connected in parallel are installed in traction substation Mrzlo Polje in 2017 and a trial operation has been started since the beginning of the December 2017.

converter, reactive power compensation, traction substation