Comparative analysis of different power delivery systems using voltage stability index

Comparative analysis of different power delivery systems using voltage stability indices are of significant importance in current scenario of interconnected power systems. While analyzing transmission systems generally resistances of lines are neglected in different voltage stability indices therefore the same index cannot be used for a distribution system. Moreover, Newton-Raphson load flow method which is used for a transmission system analysis, does not converge for a distribution system. In the present work, three power delivery systems IEEE 30-bus transmission system, a 36-bus real time Indian semi-transmission systems and the IEEE 69-bus distribution system are considered to test the existing voltage stability index. For Transmission system and semi-transmission system NR load flow method and for Distribution system Teng's method of load flow is used. A voltage stability index [2] is used, as it is, for transmission system whereas for distribution system resistance value for lines is also taken into consideration in the same index. The maximum load-ability of all the buses for all the systems considered, were calculated one-by-one. The bus having least loading-ability is considered as weakest. The proposed method is efficient and gives additional information about collapse phenomenon and maximum load-ability.