Ground fault tracing: CT magnetization

When tracing ground faults on ungrounded DC systems, one should not assume that there will be no DC current flowing through the circuit. If a current clamp (CT) is placed on a line with DC current, the DC current will cause the CT, namely its iron core, to magnetize. The higher the DC current, the stronger the magnetization will be. This can make removing the CT quite difficult. The CT can be damaged in the process of removal. In some cases, the CT cannot be removed from the line.

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