PURPOSE: To detect the partial or average insulation deterioration of a cooled- magnet main body against the ground so as to automatically take such a protective means as the forcible cutoff of power supply, etc., by grounding arbitrary one point of a power unit or DC transmission cable through an electric resistor and detecting and measuring the electric current flowing through the electric resistor. ;CONSTITUTION: A power unit 5 for water-cooled magnet is connected to a water-cooled magnet main body 1 through a DC transmission cable 6 and arbitrary one point of the cable 6 is grounded through an electric resistor 8 having a high resistance. The electric current flowing through the resistor 8 is detected by means of a current detector 9 and determined by means of a current measuring instrument 11. Then the electric signal of the measuring instrument 11 is inputted to a protective setter 13 after the signal is amplified by means of an amplifier 12 and the magnitude the electric current is determined. Therefore, the magnet main body 1 can be sufficiently protected from insulation deterioration against the ground.;COPYRIGHT: (C)1996,JPO
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