The impact of 50 Hz railroad systems on utility system unbalance

50 Hz railway loads, typically supplied by two phases of the transmission system, represent a possible source of the unbalance. The penetration of the unbalance is highly dependent on the stiffness of the power system and connections from the local, public network. This paper presents observations of the unbalance caused by rail loads in two various Finnish areas. Kainuu represents a rural area of a relatively weak transmission system and heavy ore trains. On the opposite, Helsinki urban area has a stiff transmission system and train loads are proportionally considerably minor. These extreme Finnish power system characteristics result in relatively high unbalance values in Kainuu and lower values in Helsinki.