Zone can transfer more power to other zones than the generation capacity within the zone

[sriharid]

Currently, there is no constraint to limit the power that is transferred out of a load zone to the generation capacity in that zone. Due to this, if the transmission line capacity is large enough, overgeneration is allowed and the overgeneration and unserved energy penalties are such that it is cheaper to overgenerate in this zone and transfer the power to another zone, that is is chosen by the optimisation. However, such an occurence is physically not possible in a real system.

This is possibly related to issue # 986, but creating a new issue since the proposed solution here is different from #986.