Abstract
In this paper a computer package-NETOMAC, which is developed by Siemens power transmission and distribution group and used to analyze system voltage collapses in time-domain, is presented. The components, which significantly affect the voltage stability, are modeled in detail with the NETOMAC controllers in the simulation process. The advantage of NETOMAC is that it can simulate nearly all dynamic elements such as various loads, controllers, governors and regulators in the system and nearly there is no bus number limit. Furthermore, it can show the power angle and voltage profiles at same time by which the factor of voltage collapse whether caused by angle or voltage instability is observable. For illustrative purpose a test system from CIGRE[4 ] is applied to NETOMAC and the results are promising.