| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of malfunction caused by saturation in a current transformer due to an external trouble, by detecting a maximum value of the amount of restraint among past samplings which were stored, and calculating the current sensitivity of heavy-current area properties according to the amplitude of the amount of restraint. SOLUTION: A restraint amount detecting means 12 calculates the amount of restraint, which is stored in a data memory. Respective data are read from a prescribed data memory which has stored the values of (n) samplings, and a maximum amount of restraint is detected by a maximum restraint amount detecting means 13. A current sensitivity calculating means 14 calculates the current sensitivity of heavy-current area properties according to the amplitude of the amount of restraint. It is thus possible to prevent a current differential protection relay from making an unnecessary response to the occurrence of distortion in a light-current area by changing the current sensitivity calculated from the amplitude of the amount of restraint, even if a waveform distortion occurs which is caused by saturation in a current transformer(CT) due to an external failure. |
