Digital protection relay and operation method thereof

摘要

The present disclosure relates to a digital protection relay and an operation method of the digital protection relay for enhancing the operation of a frequency change rate relay element (81R) thereof, and the digital protection relay and an operation method thereof may calculate a plurality of different frequency change rates from the measured frequency and use a value of the frequency change rate selected based on a predetermined criteria in the control of a relay operation, thereby providing an effect of enhancing reliability for the operation of the frequency change rate relay element.

主权项

1. A digital protection relay, comprising:
a frequency measurement unit configured to measure a frequency of an input signal using a zero-crossing scheme, wherein the frequency is defined by the following equation: f=1/T where f denotes a frequency (Hz) and T denotes a period (sec); a frequency change rate calculation unit configured to calculate a frequency change rate of the frequency for each of a plurality of predetermined periods of the input signal to acquire first data, and accumulate and average the measured frequency for the plurality of predetermined periods and then calculate a frequency change rate of the averaged frequency to acquire one or more second data; a deviation calculation unit configured to calculate a deviation of consecutive frequency change rates of the first or second data for a predetermined interval of time; and an operation controller configured to compare the deviation of the frequency change rates with a reference value, and select either one of the first data and second data based on the comparison result to control the operation of the relay.