| 摘要 |
A protection relay for protection of an electric network, comprising measuring (706) an electric signal in the network. The protection relay comprises converting (706) the measured signal to a frequency domain representation of the measured signal, generating (706) a measuring phasor (622E) based on the frequency domain representation, the phase rotation of the measuring phasor being dependent on one or more frequency components present in the measured electric signal, comparing (714) the measuring phasor to the reference phasor (620E), the phase rotation of the reference phasor being based on either a nominal or a measured frequency of the electric network, and launching (716) protection if the comparison of the of the measuring phasor and the reference phasor fulfils a predetermined criterion. |
