SOME ASPECTS OF EFFECTS OF HVDC LINKS ON TRANSIENT STABILITY OF HVAC SYSTEM.

Oscillations in an ac system arise due to faults which may be short circuits or sudden load rejections. If these oscillations build up, the system may become unstable. The conventional methods which maintain stability under such conditions are fast excitation system, fast governing and fast relaying etc. This paper deals with the deployment of a dc line in parallel with an ac line which gives a substantial positive damping to such electromechanical oscillations and in many cases prevents systems from becoming unstable.