| 摘要 |
PURPOSE:To enable the removal of effect of electromagnetic induction, by using several sensor units different in the set temperature of a temperature sensor while optical detection is employed to discriminate the type of an abnormality. CONSTITUTION:To detect abnormality of a connection 11 between power cable 12A and 12B, a light emitter and a light receiver are connected to optical connectors 18A, 18B and 18C respectively to determine whether any light receiver can receive light or not. When it can, no abnormality is judged to be present and when it can not, abnormality is judged to exist. At the periodical inspection, a third temperature sensor 17C is used to examine whether the temperature of the connection 11 exceeded a specified temperature in the past or not. In case of a trouble in a cable line, a first and second temperature sensors 17A and 17B are checked. If only the second temperature sensor 17B is in operation, no electric breakdown occurs at the connection but undoubtedly a short-circuit current runs, which enables the judgement that a breakdown occurs somewhere else. When the temperature sensors 17A and 17B are in operation, an electric breakdown can be judged to be present at the connection.
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