Swedish distribution networks-a new method for earthfault protection in cable- and overhead systems

For reliability as well as other reasons, an increasing number of overhead distribution lines are being replaced by cable feeders. This in turn makes it necessary to review the efficiency of existing protection concepts. Encouraged by recent changes of safety regulations in Sweden, a static device for residual current compensation (RCC) has been developed. The RCC-device is capable of suppressing arcing single phase faults even in cable systems; it thereby restores a very cost efficient way for earth fault protection with a minimum of disturbance to subscribers. The author describes the measurement method which is used to gain suitable control parameters for the RCC-device. The method also provides distance-to-earth fault information