Why Sending End voltage increased with increase in power export.?

Question

3 X 1000 KW Hydro Power Plant is connected to 11 KV grid Substation through 11 KV transmission line of length 17 KM. When power export from this Hydro Plant to 11 KV substation grid is increased from 0 to 3000 KW the sending end (Generation end) voltage is also increased proportionally from 11 KV to 12.5 KV. While voltage at recieving end (Substation end) remain constant. P.F at recieving and sending ends remain constant and maintained as 0.95 (Lagging)

Answer 1

Sounds as of the power level at the sending end was automatically or manually increased as the demand increased. This would have been to maintain 11KV at the substation end.