Contents Introduction
A HSR is currently under construction in Taiwan to reduce the traffic density on the road between Taipei and Kaohsiung. The HSR will effectively reduce travel time. In the future, the transportation network in Taiwan will be improved by integrating the Mass Rapid Transport (MRT) systems in cities on the HSR railway line. Seven substations, located along the railway, supply electrical power to the traction loads of HSR. The Taiwan Power Company (TPC) provides electrical energy to each HSR substation from the 161kV power grid. This power supply arrangement is known as a center-feed system. The power-supply is the AC system. Moreover, the rated power of thyristor controlled electric locomotives for haul has a range between 4.8 MVA and 6.4 MVA. The working capacity of Scott transformer at traction substations attained 80MVA. HIGH Speed Railway (HSR) is currently under construction in Taiwan to reduce the traffic density on the road between Taipei and Kaohsiung. The HSR will effectively reduce travel time. In the future, the transportation network in Taiwan will be improved by integrating the Mass Rapid Transport (MRT) systems in cities on the HSR railway line. Seven substations, located along the railway, supply electrical power to the traction loads of HSR. The Taiwan Power Company (TPC) provides electrical energy to each HSR substation from the 161kV power grid via two independent 25KV feeders that provide power to the HSR in opposite directions from each substation. This power supply arrangement is known as a center-feed system. The power-supply is the AT system. Moreover, the electrical power is converted from three-phase to two single phases at each HSR substation. However, single-phase loads unbalance the power system. Consequently, TPC requires the HSR's contractor to use a specially connected transformer to ensure power supply quality. This work studied the fundamental characteristics of the se specially connected transformers, i.e., Single-phase, V-V, Wye-Delta, Scott, Le Blanc, and Modified Woodbridge connected transformers. Each specially connected transformer provides two single sources on its secondary. The traditional method of describing the voltage unbalances associated with various specially connected transformers [1]–[3] assumes that the planning loads on each single source are correlated, and therefore does not truly express the degree of unbalance which may be experienced when the two sources are unequally loaded. Furthermore, the planning load of specially connected transformers can be obtained based on the train dispatch schedule.
