| 摘要 |
PROBLEM TO BE SOLVED: To provide a protection method by which equipment to be protected can be protected even when protecting operations are started a relatively short time after preceding protecting operations and which takes the temperature of the equipment into consideration. SOLUTION: In a protection method, equipment to be protected is protected from an excessive temperature rise which occurs by conduction by disconnecting the equipment from a power source-side circuit by providing an overcurrent relay, to which an inverse time lag characteristic taking the temperature rise into consideration is given, between the equipment and power source-side circuit and monitoring the current flowing to the equipment. When the equipment is restarted after the power supply to the equipment is stopped, the temperature drop of the equipment from a value related to the thermal time constant of the equipment corresponding to the power supply stopping time of the equipment and protecting operations are performed in accordance with the inverse specifies time characteristic by calculating the temperature rise caused by the power supply at the restarting time from the dropped temperature. |
