A static VAR system has been considered located at the middle of a long transmission line, and the effect of the SVS auxiliary controllers on the system dynamic performances has been examined over a wide range of operating conditions. The performance of auxiliary controllers has been studied when a reduced order network model, represented by a lumped parameter T-circuit, is used. The performance is compared with a system having a network model represented by single lumped parameter π-circuit on either side of SVS. It is observed that the size of the system matrix reduces significantly when the reduced order model is used. Also The accuracy of the eigenvalues of the system Is not much affected. The application of the auxiliary controllers, considerably, increases the system damping and unstable system modes are stabilized. © 1995 Taylor & Francis Group, LLC.