Abstract
We have been investigated the operational feasibility of a future metropolitan electric power system associated with highly densified cryogenic cables. A new conception of power system configuration with cryogenic cables and its operation has been proposed. Three different models of future power transmission systems in large cities of our country have been constructed as the background systems prior to introduction of cryogenic cables at the 21st century. In this paper, we take up one of the three models, which is characterized by its conventional transmission system being constructed mainly by 154 kV transmission lines stepping down directly from the 500kV outer ring without any intermediate voltage class. This paper discusses whether the power system model will be effectively operated or not together with cryogenic cables to supply demands forecasted in the period subsequent to the first decade of the 21st century. The computer simulations are carried out to obtain power flow and bus voltage distributions for a peak load period as well as for an off-peak one in the power system model. These simulations reveal that the conventional background power system should be arranged so carefully ahead of introducing the cryogenic cables to facilitate their operations.
(1) On a contingent trip of a cryogenic cable in the peak load period, all bus voltages are not expected to be kept within a tolerant zone due to high impedance of 154 kV conventional transmission lines in the power system model.
(2) It is thus proposed that the background conventional system prior to introduction of cryogenic cables should be developed not only by extension of 154kV conventional transmission lines but also by introduction of 275 kV ones.
(3) Bus voltage rises induced in the off-peak load period are reduced by effective utilization of 275kV conventional transmission lines.
