VOLTAGE COLLAPSE IN POWER SYSTEMS

Voltage stability has become an important issue in operating power systems. The reason is a higher stress level due to increasing loads in the systems. Many utilities are already experiencing such problems and the tendency is to operate closer to the margins. This calls for a more exact evaluation of the actual security level in order to prevent voltage collapse. This paper presents and discusses the use of static voltage stability indices. First, to find critical point, step by step load flow method is used. To increase the speed of calculation, a predication-correction method is presented. This method is faster but still takes lots of computing time. Based on a singular value decomposition of the power flow jacobian matrix, a more accurate method is presented. This method is depend on power flow model. At the end, the method is extended for different power flow models.