YOU CAN picture the scenario - you're drilling into a wall to put up a shelf when there's a flash and the lights go out. Shorting the cables on a buried mains cable is best avoided, but at least the RCD or MCB in the feed to that cable keeps the event brief and hopefully minimises the hazard. Should the cable you inadvertently hit be one from a photovoltaic array, however, the result can be very different. Shorting the DC cables from a PV array on your house roof won't cause a fuse to blow; in fact, the array will simply sit there merrily feeding current into the short circuit. Shorting the output of a PV array won't do any particular harm and has been used as a control strategy in some off-grid battery charging applications.
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