Abstract: The field windings of large generators of hydroelectric power stations which are continuously connected to a three-phase system and are designed to produce large capacitive powers, are fed from a "positive" main static converter, designed for 8 kA, via a field circuit. An anti-parallel "negative" auxiliary static converter designed for 600 A maintains a link current (i.sub.Z) of 200 A in a direct-current link with a link choke. To prevent overcurrents, which can be harmful for the link choke and the auxiliary static converter, in the direct-current link due to disturbances such as, for example, a short-circuit in the three-phase system or connection or disconnection of capacitor banks, a free-wheeling residual current is initiated in the direct-current link when the link current (i.sub.Z) exceeds a predeterminable first current limit value (i.sub.G1), corresponding to 120% of the nominal link current, during a minimum period of time of 0.5 ms.