Feasibility of the low frequency AC transmission

It has become hard to establish new overhead transmission lines for many reasons, and underground power cables will be adopted more in the future. A power cable has a difficulty of limitation in transmission length when it is operated in conventional AC system. An HVDC transmission can solve this problem for DC is free from charging current problem. XLPE cable is being more widely used at each voltage level instead of of cables and the other types, because it has many advantages. But XLPE cable has a difficulty of operation in DC, because space charge accumulates in the XLPE dielectrics. The authors propose a low frequency AC transmission (LFAC) to a power cable system. The proposing LFAC system uses the power electronics apparatus of AC/AC converters at the terminals. From the frequency characteristics of the space charge behavior in XLPE dielectrics, the power cable operation in higher frequency than 1 Hz can be admitted. The presenting LFAC transmission can use the conventional AC XLPE cable by operating higher than this frequency. In the paper, the authors describe other merits and demerits of the proposed LFAC transmission compared to the conventional AC transmission and an HVDC transmission. Finally, the authors present the simulation results of the simplified LFAC system model by using EMTP.