MOTOR PROTECTION RELAY

摘要

PURPOSE: A motor protection relay is provided to show a negative phase sequence current to a user by performing a DFT(Discrete Fourier Transform) operation. CONSTITUTION: A current measurement unit(310) detects the current of a wiring connected to a motor by a current transformer. A DFT operation processor(330) comprises a DFT operation unit and a negative phase sequence current operation unit and perform the DFT operation of the current measured by the current measurement unit. A negative phase sequence current operation unit calculates the negative phase sequence current by using the DFT operated value. A display unit displays the negative phase sequence current calculated by the DFT operation processor.