INTELLIGENT ZERO HARMONIC FILTER BUILT-IN RELAY

摘要

The present invention relates to a zero harmonic filter. According to an embodiment of the present invention, the zeroharmonic filter includes: a zigzag-connected transformer electrically connected to an R-phase busbar, an S-phase busbar, a T-phase busbar, and an N-phase busbar and removing zero harmonics by circulating zero harmonics in the inside; a switching unit disposed on a line to connect the zigzag-connected transformer to the R-phase busbar, the S-phase busbar, and the T-phase busbar; and a control module which calculates a zero-phase average value for each time zone by scanning a zero-phase component in an electric current on the N-phase busbar for one day whenever a predetermined time has elapsed, electrically disconnects the zigzag-connected transformer from the R-phase busbar, the S-phase busbar, the S-phase busbar, and the T-phase busbar in a time zone in which the zero-phase average value calculated from a time point when the zero-phase average value is calculated to a time point when the preset time has elapsed is equal to or less than a preset zero-phase lower limit, and connects the zigzag-connected transformer to the R-phase busbar, the S-phase busbar, and the T-phase busbar in a time zone in which the calculated zero-phase average value exceeds the preset zero-phase lower limit. The control module updates the zero-phase average value of one day for each time zone whenever the preset time has elapsed, and connects or disconnects the zigzag-connected transformer to or from the R-phase busbar, the S-phase busbar, and the T-phase busbar during the preset time by using the updated zero-phase average value of one day for each time zone.