Förfarande för att efter det att ett fel har inträffat i ett kraftnät mäta och återskapa fasströmmarna samt anordning för genomförande av det nämnda förfarandet

摘要

A method and a device, after a fault has occurred in a power network, for measuring and recreating the phase currents IB prior to the occurrence of the fault by determining continuously, starting from sampled measured values of the phase currents up to the time of the fault for each phase, the amplitude I and the phase angle phi of the phase currents based on two consecutive sampled measured values, whereupon a comparison is made between the last determined value Ik obtained and the rated current In of the power network. If Ik is greater than In, it is considered that a fault has occurred and the phase currents prior to the fault are indicated as IB=Ik-1xsin ( phi k-1+ omega (t-tk-1)).