H3C WX3000 Installation Manual page 98

If the multimeter displays that the left wire is the zero wire and the right is the live wire, it means that
the PE terminal of the arrester is not well grounded.
Otherwise, it means that the power receptacle of the arrester is set to the reverse polarity. In this
case, open the power receptacle of the arrester and correct the polarity. After that, if the red LED
still alarms, it means that the arrester is not well grounded yet.
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