| 摘要 |
PROBLEM TO BE SOLVED: To prevent a loss of electric energy and damage to equipment and generation of an accident resulting in injury or death by enabling a simple and accurate detection of degradation in electric insulation performance of a furnace material in an electric melting furnace in which an electric insulating furnace material is used. SOLUTION: An electric melting furnace K is provided with a melting furnace body 3 composed of an electric insulating furnace-material 3a and a shell 3b covering the material 3a, and a DC source apparatus 8 for electric energy supply to the furnace body 3. The shell 3b of the furnace body 3 is grounded, and a grounding resistor R is inserted between output terminals of the DC source apparatus 8, and the center thereof is grounded. A grounding fault current Ig flowing in a grounding wire L1 on the shell 3b or grounding wire L2 on a grounding resistor R is continuously detected to detect a degradation in the performance of electric insulation of the furnace material 3a from the detected value of the grounding fault current Ig, and the operation shutdown of the furnace K is controlled.
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