ANALYSIS OF SYMPATHETIC INRUSH DUE TO PARALLEL POWER TRANSFORMER ENERGIZATION AND ITS DETECTION BY DIFFERENTIAL RELAYING

摘要

In this paper an analysis of sympathetic inrush and a proposal to discriminate this condition for the normal inrush is presented. Sympathetic inrush is due to the energization of a transformer when another is connected in parallel and already energized. This condition is analyzed as a cause of the reduction in the levels of the ratio 2nd/1st order harmonics of the differential currents used in the conventional relaying techniques. It follows that the threshold setting is complicated; in some cases the ratio is so distorted that unwanted tripping can be issued. This paper discussed the way in which sympathetic inrush is produced in power systems, and how a detection method based on the terminal voltage observation can be applied to narrow the thresholds during this special condition.