| 摘要 |
PROBLEM TO BE SOLVED: To realize a temperature calculation type overload protective relay 3, which can eliminate unnecessary cut-offs of a load, even if the load has much fluctuations such as flicker load, and which enables stable operation. SOLUTION: Currents, flowing through monitor lines 1L and 2L, are detected and weather conditions (the temperature, wind velocity, and sunshine) around the monitor lines 1L and 2L are detected. The wire temperatures of the monitor lines 1L and 2L are estimated, according to the detected current values and weather conditions and are compared with a set value to decide the overload conditions of the monitor lines 1L and 2L. With such a constitution, since the overload conditions are decided according to the wire temperature estimated taking the weather conditions into account, the frequency of unnecessary cut-offs of a load is reduced, and hence more stable power supply can be realized, in comparison with a case using a conventional overload protective relay which decides overload states, according to a current value only and controls the conditions according to the total time of overload periods, and hence more stable power supply can be realized. |
