Voltage stability improvement of a reactive power constrained longitudinal network feeding predominantly agricultural loads in scattered remote areas

This paper focuses on voltage stability improvement of an isolated longitudinal system of Quetta in Baluchistan province in the western region of Pakistan. The regional system of Quetta has little local generation, poor reactive power support and is mainly fed from the National grid through a very long 220 kV radial transmission link while its network configuration also comprises of many long radial 132 kV lines feeding predominantly agricultural (tube-well motor) load in remotely scattered areas. Quetta power system experiences voltage instability/collapse when load demand rises or any contingency occurs. In this paper, the results of static and dynamic simulations have been presented to analyze and improve the voltage stability of Quetta system by using various reactive compensation options. The effectiveness of the proposed solution comprising of switched capacitors and FACTS controllers as well as impact of their sizes, locations and parameter variation has been demonstrated to improve voltage stability of the peculiar longitudinal system of Quetta.