chapter  4
Phase-Shifting Transformers
Pages 18

The necessity to control the power flow rose early in the history of the development of electrical power

systems. When high-voltage grids were superimposed on local systems, parallel-connected systems or

transmission lines of different voltage levels became standard. Nowadays large high-voltage power grids

are connected to increase the reliability of the electrical power supply and to allow exchange of electrical

power over large distances. Complications, attributed to several factors such as variation in power-

generation output and=or power demand, can arise and have to be dealt with to avoid potentially

catastrophic system disturbances. Additional tools in the form of phase-shifting transformers (PSTs) are

available to control the power flow to stabilize the grids. These may be justified to maintain the required

quality of the electrical power supply.