Asea Ab

Gert Apell

Nils Brandt

Finn Andersson

A method and a device in connection with digital distance relays for obtaining a backup function in the event of faults in the digital signal processing and/or in the event of faults detected during automatic testing. The method comprises testing the distance relay continuously, in case of a faultless network, with respect to the digital signal processing by means of a central control unit. In case of a characteristic fault on the network, the distance relay is switched over from testing to protective function involving measurement by means of measurement signal units included in the distance relay. In case of a fault on the network and a simultaneous fault in the digital signal processing, fault signals from the measurement signal units, via time delay circuits and logical elements, bring about tripping of the line section subjected to the fault. When a fault is detected in the digital signal processing, an alarm function is triggered.

Growing community of inventors

Vaster.ang.s, Sweden

Gert Apell