If a transmission path operator sells 500 MW of its 1000 MW TTC limit, what is the ATC?

To determine the Available Transfer Capacity (ATC), one must understand its relationship with the Total Transfer Capability (TTC) and the capacity that has already been sold or reserved. In this case, the transmission path operator has a Total Transfer Capability (TTC) of 1000 MW.

If the operator sells 500 MW of this capacity, the amount of capacity that remains available for other transactions must be calculated. The ATC represents the unused portion of the TTC after accounting for the commitments already made. Thus, it is calculated as:

ATC = TTC - Reserved Capacity

Substituting the given values:

ATC = 1000 MW - 500 MW = 500 MW.

This calculation shows that, after selling 500 MW, there is still an additional 500 MW available for use by other transactions or operators, confirming that the ATC is indeed 500 MW. The choice that correctly represents this calculation is the one that states 500 MW.