System studies and basic design for an advanced series compensation scheme (ASC)

A new innovative advanced series compensation (ASC) scheme will be supplied by Siemens for installation in the 230 kV Kayenta substation by the Western Area Power Administration USA (WAPA) in early 1992. This scheme includes thyristor controlled reactors in parallel with a three-phase capacitor bank, which represents significant progress in terms of flexible AC transmission systems (FACTS). The authors describe the theory and equipment used for the ASC scheme. The following aspects of the ASC are discussed: steady state behaviour and impedance variation dependence on firing angle and line current; bang-bang control and modulation of firing angle to damp power oscillations at different frequencies; elimination of spark gaps and reduction of MOV energy using the ASC scheme; advantages of digital control and protection for the ASC scheme; fast reinsertion of the capacitor bank after fault clearing in the AC network; and smooth reinsertion of the capacitor bank