METHOD OF PROTECTION OF ELECTRICAL NETWORKS IN THE EVENT OF POWER SWINGING BY MEANS OF A SWING ARRESTER AND A SWING ARRESTER FOR THE PERFORMANCE OF THE METHOD

摘要

For the protection of electrical networks in the event of power swings, a swing arrester (P) is employed, which independently of the value of the impedance at any time continuously monitors and evaluates the alteration with time either of the measured impedance or of the voltage multiplied by the cosine of the phase shift between current and voltage. For the current connection (IR-IS) and the voltage connection (UR-US) there are employed inter alia two parallel connected pick-up-and-hold members (8, 8') the output signals from which are subtracted in a device (9) for the formation of a difference, so that the trigger circuit (10) connected after them and a counter (11) emit at the output (12) from the swing arrester (P) a logical signal only when the trigger circuit (10) emits a logical signal twice in succession within a predetermined time. With this protection the electrical networks are adequately protected in the event of power swings against incorrect trippings also in cooperation with any kind of short-circuit protective relay.