Notice that the operating voltage VF is close to the knee of
their I-V characteristics. Therefore, each string is providing the
current close to Isc. In other words, Iother is close to (n-1) Isc. Iother
has no path to go but to backfeed into String 1. As a result, Iback
at String 1 becomes (n-1) Isc, flowing into the ground-fault point F.