Voltage stability index of radial Distribution network

Distribution networks experience distinct change from a low to high load level every day. Hence, a major concern in power distribution networks, which have surfaced fairly, recently is the problem of voltage stability. In this paper in the first phase of work an attempt has been made for performing voltage stability analysis of electrical power distribution system. A formula for computing the voltage stability index (VSI) of all nodes of distribution network is verified in this paper using MATLAB version 6.5 Multiple nodes having minimum stability index have been selected first and then the node having the minimum value of voltage stability index is declared as most sensitive node. Taking example of a typical radial Distribution network, it has been shown that the node having the minimum value of VSI is the most sensitive. In the second phase of work the critical values of total real power load and total reactive power load for various cases is found out, the system will collapse beyond the computed values of critical power. It has been observed that for various cases of critical loading the node which is coming most sensitive will collapse first. The critical power obtained by various cases provide an acute information with reference to the stability condition of the weakest node, taking into account the entire system loading at a given operating point. Also graphically the comparison is made for all the cases by drawing PV curves of critical loading.