| 摘要 |
PROBLEM TO BE SOLVED: To prevent malfunction by breaking a main transformer so that the residual magnetic flux of the iron core of the main transformer may be settled within a given zero range, when a protective relay outputs a trip signal and breaks the main transformer from a power system. SOLUTION: A protective relay has a system input means 1 which measures the primary voltage V1 and current 11 and the secondary voltage V2 and current 12 of a main transformer 1, and outputs output signals 11-14. This has a protective relay operating circuit 2 which detects the accident of a power system or inside a transformer with the data 11-14 of the system input means 1, and outputs trip signals 21. A forecasting circuit 5 forecasts the timing to zero the residual magnetic fluxes of the iron core of the main transformer with the data 11-14 of the system input means 1. A logical circuit 3 takes the AND of the trip signal 21 of the protective relay operating circuit 2 and a magnetic flux forecast signal 55 of the forecasting circuit 5, and outputs a trip signal 31. Therefore, the residual magnetic flux of the iron core of the main transformer is settled within the specified zero range. |
