Transmission companies determine the utmost reputable ability of each line (ordinarily less than its Bodily or thermal Restrict) making sure that spare capacity is offered from the event of the failure in another Element of the network.P R = V 2 × I = V R R + R C × V R + R C = R R + R C × V 2 R + R C = R R + R C P V displaystyle P_ R =V_ two mom