Voltage support of radial transmission lines by var compensation at distribution buses

Voltage support of transmission lines by var compensation is now carried out mostly on transmission buses. The authors show that var compensation on distribution buses and deregulation of transmission voltages is not only feasible in certain circumstances but also economically advantageous. This opens the prospect of the distribution sector offering voltage support to the transmission sector as an ancillary service. The considered system is a 400 km long, 230 kV, heavily loaded (800 MW) radial transmission line which feeds several remote load centres spaced along its length. Analysis of the benefits and demonstration of feasibility, steady-state stability and robustness in the face of short-circuit faults are presented.