Due to the inherent connection structure between the power supplies and the superconducting magnetic coil, the power supplies are seeing each others as loads through the coil. It has been observed in the pilot test at TLS that there is about 300mA earth leakage current flowing through the earth leakage protection circuit, which presented an interlock and halted the whole system down. The existence of earth leakage current may undermine the overall system stability and pose more threat on the electronic system safety. In this paper, the earth leakage mechanisms are thoroughly examined and measures to conquer the problem are proposed.

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