DIGITAL RATIO DIFFERENTIAL PROTECTION RELAY

摘要

The present invention relates to a digital ratio differential protection relay used for main protection of a power transformer. In the related art, the relay malfunctions due to excessive excitation inrush currents when the transformer is turned on, when voltage is restored, and when the transformer is placed in parallel. When a large part of the load is separated from the relay, there is a problem that the over-excitation due to the voltage rise of the transformer terminal also causes malfunction.;In view of this, by analyzing the input current from the current transformer using the digital signal processing unit, the digital filtering technique is used to investigate the inrush situation with two harmonic components, and the over-excitation situation with the five harmonic components. It prevents malfunction of transformer and protects circuit by sending trip signal to breaker accurately and quickly in case of internal failure.;Therefore, the transformer main protection relay can be multifunctional and miniaturized, and there is a convenient effect on improving reliability and maintenance.