Transmission lines (69 kV and 138 kV) New transmission lines include a fixed cost and a variable cost. The fixed cost is for the design work, the purchase/ installation of the three-phase circuit breakers, associated relays, and changes to the substation bus structure. The fixed costs are $200,000 for a 138-kV line and $125,000 for a 69-kV line. The variable costs depend on the type of conductor and the length of the line. The assumed cos