The PV 150 is detecting greater than 30V leaking back to Earth (Ground in the US). This can happen with a genuine Earth fault (check earth continuity on individual modules in turn to find the fault), or if the reading is greater than 100V, it usually indicates that Earth and Neutral are connected together in the system. These need to be separated in the combiner box for the purpose of testing, and then re-connected before energising the system again.
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